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Morphogenesis of the compound leaf in three genotypes of the pea, Pisum sativum
Abstract
Leaf anatomy, ontogeny, and morphology were described and compared in a pea line (Pisum sativum L.) with conventional leaves and in isogenic lines carrying the mutations af (afila) or tl (tendril-less or acacia). The anatomy of stem, petiole, and rachis is not modified by these mutations. The tendrils, which in af replace leaflets, have normal tendril anatomy, and the terminal leaflets of the tl form have normal leaflet anatomy. The shoot apical dome has the same size and shape in the three genotypes, as does the leaf primordium up to the stage of initiation of the first laterals. The mature morphology of leaves varies with node of insertion. Some leaves, especially at nodes 3 and 4, have structures that are not typical of their genotype. An in vitro culture system is described for axillary shoots. Such shoots recapitulate most of the foliar features of seedling plants, but leaf morphology is on average more complex, and aberrant structures are more frequent. All these observations are discussed in relation to Young's algebraic model for compound leaf development.
... During P3 and P4, the terminal unifoliate leaflet expanded, began to fold, and initiated epidermal hairs at its tip ( Figure 2D). previously by several authors (Meicenheimer et al., 1983;Gould et al., 1986;DeMason, 1997, 1999a). A brief SEM analysis of near-isogenic lines of these genotypes-JI 1194, JI 1197, JI 1195, and JI 1199, respectively-is presented in Figure 3 to facilitate the identification of those structures labeled in subsequent in situ hybridization sections. ...
... The function of TL in the suppression of blastozone activity in the tertiary lateral primordia of af mutant leaves was first apparent during P5. Our observations of changes during leaf ontogeny were in broad agreement with those made in earlier studies that compared wild-type and mutant leaf development (Meicenheimer et al., 1983;Gould et al., 1986;DeMason, 1997, 1999a). Because previous reports had provided genetic evidence to suggest that UNI, AF, and TL interact to pattern the pea leaf (Marx, 1987;Ellis, 1996, 1998), we examined UNI expression in the wild type, tl, af, and af tl mutants to deter- A, shoot apex; P1 to P4, plastochron 1 to plastochron 4 of leaf development; S1 to S3, stipule primordia present on P1 to P3 marginal blastozones; L2 to L4, proximal leaflet primordia present on P2 to P4 marginal blastozones; T3 and T4, tendril primordia present on P3 and P4 marginal blastozones. ...
... Organ primordia initiated from the marginal blastozone during P2 on af single mutant and af tl double mutant leaves are morphologically indistinguishable from those of wildtype plants and tl mutants at this stage (Meicenheimer et al., 1983;Gould et al., 1986;DeMason, 1997, 1999). Differences between these four genotypes first occur during P3, when these first-initiated organ primordia (which would form determinate leaflets in wild-type and tl mutant leaves) behave like blastozones in af and af tl leaves (Figures 3E and 3G) and initiate tertiary primordia. ...
The compound leaf primordium of pea represents a marginal blastozone that initiates organ primordia, in an acropetal manner, from its growing distal region. The UNIFOLIATA (UNI) gene is important in marginal blastozone maintenance because loss or reduction of its function results in uni mutant leaves of reduced complexity. In this study, we show that UNI is expressed in the leaf blastozone over the period in which organ primordia are initiated and is downregulated at the time of leaf primordium determination. Prolonged UNI expression was associated with increased blastozone activity in the complex leaves of afila (af), cochleata (coch), and afila tendril-less (af tl) mutant plants. Our analysis suggests that UNI expression is negatively regulated by COCH in stipule primordia, by AF in proximal leaflet primordia, and by AF and TL in distal and terminal tendril primordia. We propose that the control of UNI expression by AF, TL, and COCH is important in the regulation of blastozone activity and pattern formation in the compound leaf primordium of the pea.
... In the afaf background, the distal-most tips of the proximal, branched pinnae and the distal, simple pinnae are slightly flattened (Fig. 1 E ;Lu et al., 1996 ;Villani and DeMason, 1999 b). The broad tendril\narrow leaflets in the Tltl heterozygotes are anatomically similar to true leaflets in wildtype plants and leaflets at all positions on Af\-plants, in that they possess recognizable palisade parenchyma and spongy mesophyll, although there is little intercellular space and cell shapes are not as well defined (Gould et al., 1986 ;DeMason, 1997, 1999 b). Furthermore, although the broad tendril\narrow leaflets are narrower than true leaflets in the distal positions of Afaftltl plants ( Fig. 1 B-D), their palisade and spongy mesophyll cells are larger (Villani and DeMason, 1999 b). ...
... They stated that pinna initiation is basipetal in the terminal domain because differentiation and expansion of the terminal pinna precedes initiation of the ultimate lateral pinna pair (Hofer and Ellis, 1998). Previous authors (Gould et al., 1986 ;Co# te! et al., 1992 ;Villani and DeMason, 1997) had already shown clearly that lateral pinna pair initiation on wildtype leaves is strictly acropetal (toward the tip), but the exact timing of terminal pinna differentiation has not previously been evaluated. The terminal pinnae on leaves of plants heterozygous at the Af and\or Tl loci possess all possible morphologies : tendril (AfafTlTl ), leaflet (Afaftltl) and broad tendril\narrow leaflet (Af-Tltl ) (Fig. 1), and the relative timing of differentiation events during leaf development in these genotypes might shed light on whether the terminal pinna should be considered a separate region\domain, either combined with all of the lateral pinnae in the distal region or only with the ultimate lateral, pinna pair. ...
... The wildtype, acacia, afila and aftl double mutant genotypes exhibit heteroblastic leaf variation (an ontogenic progression in which early or juvenile structures are different from later or adult ones). Leaves at lower nodes are smaller and have fewer lateral pinna pairs than leaves at upper nodes (Gould et al., 1986(Gould et al., , 1992Lu et al., 1996 ;DeMason, 1997, 1999 a). Using these criteria to analyse the relative rates of shoot ontogeny, the Af and Tl genes appear to interact to modify shoot development. ...
The wildtype leaf blade of Pisum sativum possesses proximal leaflets and distal tendrils, which may be altered by two recessive mutations that affect pinna morphology,
afila (afaf) and tendrilless (tltl). Using morphological observations and SEM, the variation in leaf forms along the plant axis and leaf development were characterized
for plants heterozygous at the Af and/or Tl loci. The Af and Tl genes interacted to affect many characteristics of shoot ontogeny, including rate changes in leaf blade length and complexity
increases, as well as time to flowering. The Af gene retarded early vegetative development and accelerated the time to flowering. The leaf phenotypes of these heterozygous
genotypes were specified mainly by changes in the timing of major developmental events. The data support the hypotheses that
both genes are heterochronic in nature and that the pea leaf blade consists of three genetically- and developmentally- determined
regions: proximal, distal and terminal. Copyright 2000 Annals of Botany Company
... In the afaf background, the distal-most tips of the proximal, branched pinnae and the distal, simple pinnae are slightly flattened (Fig. 1 E ;Lu et al., 1996 ;Villani and DeMason, 1999 b). The broad tendril\narrow leaflets in the Tltl heterozygotes are anatomically similar to true leaflets in wildtype plants and leaflets at all positions on Af\-plants, in that they possess recognizable palisade parenchyma and spongy mesophyll, although there is little intercellular space and cell shapes are not as well defined (Gould et al., 1986 ;DeMason, 1997, 1999 b). Furthermore, although the broad tendril\narrow leaflets are narrower than true leaflets in the distal positions of Afaftltl plants ( Fig. 1 B-D), their palisade and spongy mesophyll cells are larger (Villani and DeMason, 1999 b). ...
... They stated that pinna initiation is basipetal in the terminal domain because differentiation and expansion of the terminal pinna precedes initiation of the ultimate lateral pinna pair (Hofer and Ellis, 1998). Previous authors (Gould et al., 1986 ;Co# te! et al., 1992 ;Villani and DeMason, 1997) had already shown clearly that lateral pinna pair initiation on wildtype leaves is strictly acropetal (toward the tip), but the exact timing of terminal pinna differentiation has not previously been evaluated. The terminal pinnae on leaves of plants heterozygous at the Af and\or Tl loci possess all possible morphologies : tendril (AfafTlTl ), leaflet (Afaftltl) and broad tendril\narrow leaflet (Af-Tltl ) (Fig. 1), and the relative timing of differentiation events during leaf development in these genotypes might shed light on whether the terminal pinna should be considered a separate region\domain, either combined with all of the lateral pinnae in the distal region or only with the ultimate lateral, pinna pair. ...
... The wildtype, acacia, afila and aftl double mutant genotypes exhibit heteroblastic leaf variation (an ontogenic progression in which early or juvenile structures are different from later or adult ones). Leaves at lower nodes are smaller and have fewer lateral pinna pairs than leaves at upper nodes (Gould et al., 1986(Gould et al., , 1992Lu et al., 1996 ;DeMason, 1997, 1999 a). Using these criteria to analyse the relative rates of shoot ontogeny, the Af and Tl genes appear to interact to modify shoot development. ...
The wildtype leaf blade of Pisum satiäum possesses proximal leaflets and distal tendrils, which may be altered by two recessive mutations that aect pinna morphology, afila (afaf) and tendrilless (tltl). Using morphological observations and SEM, the variation in leaf forms along the plant axis and leaf development were characterized for plants heterozygous at the Af and}or Tl loci. The Af and Tl genes interacted to aect many characteristics of shoot ontogeny, including rate changes in leaf blade length and complexity increases, as well as time to flowering. The Af gene retarded early vegetative development and accelerated the time to flowering. The leaf phenotypes of these heterozygous genotypes were specified mainly by changes in the timing of major developmental events. The data support the hypotheses that both genes are heterochronic in nature and that the pea leaf blade consists of three genetically- and developmentally- determined regions: proximal, distal and terminal. # 2000 Annals of Botany Company
... In a major review of pea leaf development mutants, Marx (1987) suggested that various mutants appear to operate in these three dierent`domains' within the leaf (basal, proximal and distal), and that the action of these leaf development genes might help to de®ne these areas. However, studies of pea leaf development have concentrated on the recessive mutant a®la(af) (Kujala, 1953;Goldenberg, 1965), the semidominant mutant tendril-less(tl) (Vilmorin and Bateson, 1911) and the af tl double mutant (Fig. 1D, F and G), which alter lea¯et and tendril pinna identity in the proximal and distal domains (Meicenheimer et al., 1983;Gould et al., 1986Gould et al., , 1994Cote et al., 1992;Lu et al., 1996;Villani and DeMason, 1997, 1999a, b, 2000. The stipules and basal compartment have received little attention, with only one model of pea leaf development (Gourlay et al., 2000) considering the cochleata (coch) mutant (Wellensiek, 1959), in which the stipules of the middle nodes of the plant are compound (Fig. 1B). ...
... Meristem size has been linked to the size of the structures they produce (Smith and Hake, 1992;Sundberg and Orr, 1996;Lijsebettens and Clarke, 1998;Jackson and Hake, 1999). It has been suggested that dierences in meristem or primordial size could produce dierent pea leaf mutants (Young, 1983;Gould et al., 1992), although no size dierence was found in the meristems of af, tl and af tl mutants (Meicenheimer et al., 1983;Gould et al., 1986;Cote et al., 1992). Here, we examine the early leaf development of coch and unifoliata (uni) (Eriksson, 1929) mutants to investigate the role of meristem size in the development of dierent types of leaf structures in addition to lea¯ets and tendrils. ...
... The eects of the mutations coch and uni seem to be apparent at an earlier stage (late P 1 to early P 2 ) of leaf primordia development than the mutants tendril-less and a®la (apparent late P 4 ±P 6 and late P 2 ±P 3 , respectively) (Meicenheimer et al., 1983;Gould et al., 1986;Gourlay et al., 2000;Villani and DeMason, 2000), so they may act earlier in the leaf developmental pathway. No dierences in the size of the shoot apical dome have previously been reported in pea leaf mutants. ...
The stipule mutant cochleata(coch) and the simple-leaf mutantunifoliata (uni) are utilized to increase understanding of the control of compound leaf and flower development in pea. The phenotype of the coch mutant, which affects the basal stipules of the pea leaf, is described in detail. Mutant coch flowers have supernumerary organs, abnormal fusing of flower parts, mosaic organs and partial male and female sterility. The wild-type Coch gene is shown to have a role in inflorescence development, floral organ identity and in the positioning of leaf parts. Changes in meristem size may be related to changes in leaf morphology. In the coch mutant, stipule primordia are small and their development is retarded in comparison with that of the first leaflet primordia. The diameter of the shoot apical meristem of the uni mutant is approx. 25% less than that of its wild-type siblings. This is the first time that a significant difference in apical meristem size has been observed in a pea leaf mutant. Genetic controls in the basal part of the leaf are illustrated by interactions between coch and other mutants. The mutantcoch gene is shown to change stipules into a more ‘compound leaf-like’ identity which is not affected by thestipules reduced mutation. The interaction of coch and tendril-less(tl) genes reveals that the expression of the wild-type Tl gene is reduced at the base of the leaf, supporting the theories of gradients of gene action.
... The use of near isogenic lines provides an opportunity to study the genetic regulation of leaf development by allowing morphological and developmental comparisons between plants that differ only by single genes. A set of near isogenic lines developed by G. A. Marx has been used by various researchers (Gould, Cutter and Young, 1986, 1994Gould, Young and Cutter, 1992 ;Lu et al., 1996 ;Villani and DeMason, 1997). Gould et al. (1992) used L-system analysis to describe complexity of pea leaf pinnae and found that afila and pleiofila are more complex and variable than wildtype and acacia phenotypes. ...
... Various authors have attempted to describe the developmental events that lead to the observed leaf phenotypes (Meicenheimer et al., 1983 ;Gould et al., 1986Gould et al., , 1994Cote et al., 1992 ;Lu et al., 1996 ;Villani and DeMason, 1997). Gould et al. (1986) first described the developmental events that give rise to embryonic and early postembryonic leaves on afila compared to the other phenotypes. ...
... Various authors have attempted to describe the developmental events that lead to the observed leaf phenotypes (Meicenheimer et al., 1983 ;Gould et al., 1986Gould et al., , 1994Cote et al., 1992 ;Lu et al., 1996 ;Villani and DeMason, 1997). Gould et al. (1986) first described the developmental events that give rise to embryonic and early postembryonic leaves on afila compared to the other phenotypes. They showed that there is no difference in the initial appearance of leaf primordia, or sequence of pinna initiation (acropetal) among wildtype, acacia or afila phenotypes, but that pinnae were initiated later in afila than in wildtype or acacia. ...
The wildtype leaf of the garden pea possesses proximal pairs of leaflets and distal pairs of tendrils in the blade region. Theafila (af) mutation causes leaflets to be replaced by compound (branched) tendrils. We characterized the morphological variation in leaf form along the plant axis and leaf development in early and late postembryonic leaves onafilaplants to infer the role of theAfgene. Leaf forms are more diverse early in shoot ontogeny onafilaplants.Afinfluences pinna length and pinna branching in addition to pinna type. Pinna initiation in the proximal region ofafilaleaf primordia is basipetal and delayed compared to wildtype plants. In addition, pinna development in the proximal region ofafilaleaves occurs for a longer period of time than on wildtype leaf primordia. Therefore,Afregulates the timing and direction of leaf developmental processes in the proximal region of the leaf, but has little effect on the distal region. These data support the heterochronic model of pea leaf morphogenesis proposed by Luet al. (International Journal of Plant Science157: 311–355, 1996).
... Leaves were numbered in acropetal order, with the cotyledonary node designated as node 1. Measurements were conducted in two phases: (1) nodes 4-17 were measured as soon as leaf 17 was fully expanded; and (2) nodes 18-27 were measured as soon as leaf 27 was fully expanded. Leaves at nodes 2 and 3 were not measured because they are scalar leaves without any lateral structures and show no discernible differences in morphology (Gould, Cutter, and Young, 1986). Pinna positions within a leaf were also numbered in acropetal order. ...
... primordia at nodes 16-18 (late postembryonic leaves) were initiated as lateral outgrowths of the shoot apical meristem in a manner similar to early postembryonic leaves (Lyndon,1970, 1971Meicenheimer et al., 1983;Gould, Cutter, and Young, 1986). During P 2 (second plastochron), pinnae at positions 1 and 2 were initiated in an acropetal sequence (Fig. 10). ...
... Although the wild-type pea leaf is typically symmetrical such that leaflets occur opposite leaflets and tendrils opposite tendrils, asymmetries in the form of mixed pairs also occur. Using L-system analysis, Gould, Cutter, andYoung (1992)showed that asymmetric leaves also occur in afila and aftl genotypes.Lu et al. (1996)plotted the position of mixed pinna pairs on wild-type, afila, and pleiofila leaves and found that they occur only at the boundary between the distal and proximal regions of the leaf. Here we report that leaves with mixed pairs occur at specific nodal positions on wild-type plants and mark positions on the shoot where leaf complexity increases such that an additional pair of pinnae is added to the proximal compartment of the leaves. ...
The pleiofila phenotype (afaftltl double mutant) of Pisum sativum arises from two single-gene, recessive mutations known to affect the identity of leaf pinnae, afila (af), and acacia (tl). The wild-type leaf consists of proximal leaflets and distal tendrils, whereas the pleiofila leaf consists of branched pinnae terminating in small leaflets. Using morphological measurements, histology, and SEM, we characterized the variation in leaf form along the plant axis, in leaflet anatomy, and in leaf development in embryonic, early postembryonic, and late postembryonic leaves of aftl and wild-type plants. Leaves on aftl plants increase in complexity more rapidly during shoot ontogeny than those on wild-type plants. Leaflets of aftl plants have identical histology to wild-type leaflets although they have smaller and fewer cells. Pinna initiation is acropetal in early postembryonic leaves of aftl plants and in all leaves of wild-type plants, whereas in late postembryonic leaves of aftl plants pinna initiation is bidirectional. Most phenotypic differences between these genotypes can be attributed to differential timing (heterochrony) of major developmental events.
... Xanthium sp. is the most widely studied using the plastochron index formula given by Erickson and Michelini (1957). Plant processes such as leaf development (Maksymowych 1959;Maksymowych and Erickson 1960), petiole development and xylem differentiation (Maksymowych and Maksymowych 1982), incorporation of 14 CO 2 into soluble proteins (Loewenberg 1970), chloroplast growth (Holowinsky et al. 1965), changes in isoenzyme patterns (Chen et al. 1970), and flower initiation (Jacobs 1972) (Miller 1960), stipule length and width (Meicenheimer et al. 1983), leaf length (Wimmers and Turgeon 1991) and some researchers working with primodia tissues such as Gould and Cutter (1985) used an arbitrary plastochron value depending on the relative size of the leaf primodium. Clearly, an argument can be made for using PI but that thus requires the use of an accurate and functional PI formula; resulting in a constructive growth model of the plant; which can serve as a predictor of the structurefunction state of the plant. ...
... Several studies were subsequently undertaken using P. sativum using the plastochron index. For example, the correlation of leaf plastochron age with Hill-reaction activity of chloroplasts (Miller 1960); meristem characteristics of genetically modified pea leaf primodia (Meicenheimer et al. 1983); changes in volume and cell number in the different regions of the shoot apex (Lyndon 1968); morphogenesis of the compound leaf in three genotypes of the pea (Gould and Cutter 1985); appearance of transfer cells and solute uptake in minor veins of P. sativum leaves (Wimmers and Turgeon 1991); pea leaf, leaflet and tendril determination from primodia (Gould et al. 1994). Most of these studies were carried out using other parameters (based on authors' discretion) than internode length and values other than 20 mm. ...
... Meicenheimer et al. (1983) determined shoot age by using the measured radii from the central protoxylem elements, or procambium of each leaf primodium to the center of the apical meristem. Gould and Cutter (1985) defined the plastochron age of a leaf primodium as the number of visible leaf primodia initiated on the shoot meristem after its own initiation plus one. Gould and Cutter (1985) gave a leaf primodium an arbitrary plastochron value depending on its relative size. ...
Thesis (Ph.D. (Botany)) - Rhodes University, 2006.
... Leaf primordium initiation and early development in wildtype , tl , af , and af tl pea leaves have been described in detail previously by several authors (Meicenheimer et al., 1983; Gould et al., 1986; Villani and DeMason, 1997, 1999a). A brief SEM analysis of near-isogenic lines of these genotypes—JI 1194, JI 1197, JI 1195, and JI 1199, respectively—is presented in Figure 3 to facilitate the identification of those structures labeled in subsequent in situ hybridization sections . ...
... The function of TL in the suppression of blastozone activity in the tertiary lateral primordia of af mutant leaves was first apparent during P5. Our observations of changes during leaf ontogeny were in broad agreement with those made in earlier studies that compared wild-type and mutant leaf development (Meicenheimer et al., 1983; Gould et al., 1986; Villani and DeMason, 1997, 1999a). Because previous reports had provided genetic evidence to suggest that UNI, AF, and TL interact to pattern the pea leaf (Marx, 1987; Hofer and Ellis, 1996, 1998), we examined UNI expression in the wild type, tl, af, and af tl mutants to ...
... Leaf primordium initiation and early development in wildtype , tl , af , and af tl pea leaves have been described in detail previously by several authors (Meicenheimer et al., 1983; Gould et al., 1986; DeMason, 1997, 1999a). A brief SEM analysis of near-isogenic lines of these genotypes—JI 1194, JI 1197, JI 1195, and JI 1199, respectively—is presented inFigure 3 to facilitate the identification of those structures labeled in subsequent in situ hybridization sections . ...
The compound leaf primordium of pea represents a marginal blastozone that initiates organ primordia, in an acropetal manner, from its growing distal region. The UNIFOLIATA (UNI) gene is important in marginal blastozone maintenance because loss or reduction of its function results in uni mutant leaves of reduced complexity. In this study, we show that UNI is expressed in the leaf blastozone over the period in which organ primordia are initiated and is downregulated at the time of leaf primordium determination. Prolonged UNI expression was associated with increased blastozone activity in the complex leaves of afila (af), cochleata (coch), and afila tendril-less (af tl) mutant plants. Our analysis suggests that UNI expression is negatively regulated by COCH in stipule primordia, by AF in proximal leaflet primordia, and by AF and TL in distal and terminal tendril primordia. We propose that the control of UNI expression by AF, TL, and COCH is important in the regulation of blastozone activity and pattern formation in the compound leaf primordium of the pea.
... The parsley-leaved peas also lack stipules and tendrils, and have numerous minute leaflets where the tendrils normally would be. These kind of leaves (multiple imparipinnate leaves: Makasheva, 1983), form as a result ofinteractions between the recessive alleles af and tl (Gould et al., 1986). For stylistic convenience, herein we will refer to the aca-cia as 'leafy' because oftheir large, flat leaflets, and the parsley-leaved ones as 'leafless' when discussing these two varieties. ...
... comm.), and both varieties set seed cleistogamously. Further details on the biology of these varieties can be found in Gritton (1972), Marx (1974), Sharma (1972), Hedley and Ambrose (1981), Snoad (1981), Gould et al. (1986), and Ellison and Rabinowitz (1989). ...
We investigated the hypothesis that plant form can dramatically affect plant competitive ability, and that forms with dense canopies can invade populations of plants with more open canopies regardless of initial relative frequencies. Under controlled field conditions, we examined the effects of plant form on growth rate, size variation, mortality, and reproduction in high-density monocultures and mixtures of two morphologically distinct varieties of peas. These two varieties differ genetically at only the afila locus. In high-density monocultures and mixtures, peas with finely dissected, minute leaflets (af/af) grew more slowly and produced fewer seeds than Af/-individuals with large leaflets that cast more shade on neighbors. After as few as four generations, mixtures begun with 10% Af/- peas would be expected to evolve to Af/- monocultures. We conclude that an increase in morphological complexity (e.g., virtually leafless to leafy) can have dramatic ecological and evolutionary impacts on plant population dynamics.
... The novel function of UNI in regulating leaf morphogenesis is supported by the presence of PEAFLO mRNA during the first four plastochrons after leaf primordium initiation ( Figure 5), at the time when pea leaf pattern is established [21,22]. Strong PEAFLO expression was detected in petiole-rachis progenitor cells of the P1 primordium, at a stage prior to the differentiation of leaf lateral organs [25,26]. In older primordia, P4-P6, PEAFLO transcript levels were reduced in the rachis; strong expression was confined to newly developed lateral appendages, corresponding to rachilla and leaflet primordia in this genotype (Figure 5a). ...
... Leaf shape in tomato, another species with compound leaves, can be manipulated by overexpression of a different gene, KNOTTED [6]. It is possible that different regulatory mechanisms operate in pea and tomato, which are distinguished by acropetal and basipetal leaf development, respectively [7,26]; analysis of a range of species will be required to ascertain whether FLO/LFY homologues play a role in the morphogenesis of all types of compound leaves, or only in leaves with acropetally-initiating lateral organs. ...
The vegetative phenotype of the pea mutant unifoliata (uni) is a simplification of the wild-type compound leaf to a single leaflet. Mutant uni plants are also self-sterile and the flowers resemble known floral meristem and organ identity mutants. In Antirrhinum and Arabidopsis, mutations in the floral meristem identity gene FLORICAULA/LEAFY (FLO/LFY) affect flower development alone, whereas the tobacco FLO/LFY homologue, NFL, is expressed in vegetative tissues, suggesting that NFL specifies determinacy in the progenitor cells for both flowers and leaves. In this paper, we characterised the pea homologue of FLO/LFY.
The pea cDNA homologue of FLO/LFY, PEAFLO, mapped to the uni locus in recombinant-inbred mapping populations and markers based on PEAFLO cosegregated with uni in segregating sibling populations. The characterisation of two spontaneous uni mutant alleles, one containing a deletion and the other a point mutation in the PEAFLO coding sequences, predicted that PEAFLO corresponds to UNI and that the mutant vegetative phenotype was conferred by the defective PEAFLO gene.
The uni mutant demonstrates that there are shared regulatory processes in the morphogenesis of leaves and flowers and that floral meristem identity genes have an extended role in plant development. Pleiotropic regulatory genes such as UNI support the hypothesis that leaves and flowers derive from a common ancestral sporophyll-like structure. The regulation of indeterminancy during leaf and flower morphogenesis by UNI may reflect a primitive function for the gene in the pre-angiosperm era.
... Plant tendrils may be derived from a variety of structures, such as leaf parts, whole leaves, or stems (Bell 1991). For example, pea tendrils and leaflets can be considered as homologous structures (Gould et al. 1986), whereas tendrils in the Vitaceae seem to be modified reproductive organs (Millington 1966;Tucker and Hoefert 1968;Gerrath and Posluszny 1988). ...
Key message:
Next-generation sequencing-aided map-based cloning delimited the cucumber tendril - less1 ( td - 1 ) locus into a 190.7-kb region in chromosome 6 harboring a putative, novel-function candidate gene encoding a histone acetyltransferase ( CsGCN5 ). The tendril initiated from the lateral meristem is an important and characteristic organ for the species in the Cucurbitaceae family including cucumber (Cucumis sativus L.). While the tendril has its evolutionary significance, it also poses a nuisance in cucumber cultivation under protected environments in which tendril-less cucumber has its advantages. From an EMS mutagenesis population, we identified a tendril-less mutant B007, which was controlled by a recessive gene td-1. Through next-generation sequencing-aided map-based cloning, we show CsGCN5 (Cucumis sativus GENERAL CONTROL NONDEREPRESSIBLE 5), a cucumber gene for a histone acetyltransferase as the most possible candidate for td-1. A non-synonymous SNP in the first exon of CsGCN5 resulted in an amino-acid substitution from Asp (D) in the wild type to Asn (N) in the tendril-less mutant. The candidacy of CsGCN5 was further confirmed by multiple lines of evidence in both biparental and natural cucumber populations. Non-significant expression of CsGCN5 in multiple organs was found between the wild type and the mutant. CsGCN5 exhibited strong expression in the tendril of wild-type plants suggesting its important roles in growth and development of plant tendrils. The identification and characterization of the td-1 mutant from the present study provided a useful tool in understanding the molecular mechanisms of tendril organogenesis and investigation of novel functions of the histone acetyltransferase in cucumber.
... An epigenetic model of plant patterning asserts that meristem activities are induced, determined, and maintained through a cascade of decreasing developmental options in response to competing molecular signals (Sachs, 1991). Work with leaf mutants in Pisum sativum has shown that the compartmentalization of leaves into stipules, leaflets, and tendrils results from homeotic gene control of the size, growth, and division of leaf meristems (Gould et al., 1986;Marx, 1987, Meicenheimer et al., 1983Young, 1983). Accordingly, the FV trait may disrupt the petiole-leaf blade boundary in C. pepo by altering the distribution of a signal or signals responsible for marginal meristem activity. ...
The morphology, growth rate and anatomy of the fused vein trait were characterized in Cucurbita pepo using the inbreds NH2405 (fused vein), NH7210 (moderately fused vein), and NH614 (normal). Morphological analysis showed that the trait is characterized by a partial fusion of the five primary leaf veins. Fusion begins at the distal point of the petiole and extends along the central vein. Branching of the veins is delayed and there is a reduction of the interveinal leaf blade. Consequently, the upper leaf surface appears puckered or wrinkled. Depending on genetic background, the onset of fused vein leaf production starts at the fourth to tenth leaf stage and continues throughout vegetative growth. The extent of fusion increases with leaf number but stabilizes by the twentieth leaf stage. The maximum extent of vein fusion also varies with genetic background (5-20 cm). Though fused vein and normal inbreds differed in the rate and pattern of leaf growth, examination of F2 and BC populations revealed no significant effect of the fused vein trait on leaf number, leaf size, and rate of leaf initiation. Anatomical examination revealed different vascular patterns in the transition zone between petiole and leaf blade for normal and fused vein leaves. In normal leaves, the vascular bundles of the petiole enlarge and coalesce to form a vascular crescent. The crescent reorganizes and diverges as large vascular columns and pairs of smaller flanking vascular bundles into each vein. In contrast, two cycles of enlargement, coalescence, and dispersal occur in fused vein leaves.
... Tendrils share some developmental processes such as radial growth with typical stems (e.g. Gould and Cutter, 1986 ;Meicenheimer et al., 1983 ;Cote! et al., 1992 ;Gould et al., 1994). Therefore, it would be relevant to ask how the proteins of tendrils (such as those of peas) relate to those of stems. ...
Plant morphology, including morphogenesis, remains relevant to practically all disciplines of plant biology such as molecular genetics, physiology, ecology, evolutionary biology and systematics. This relevance derives from the fact that other disciplines refer to or imply morphological concepts, conceptual frameworks of morphology, and morphological theories. Most commonly, morphology is equated with classical morphology and its conceptual framework. According to this, flowering plants and certain other taxa are reduced to the mutually exclusive categories of root, stem (caulome) and leaf (phyllome). This ignores the fact that plant morphology has undergone fundamental conceptual, theoretical and philosophical innovation in recent times. These changes, when recognized, can fundamentally affect research in various disciplines of plant biology. They may even change the questions that are asked and thus may affect the direction of future research. If, for example, plant diversity and evolution are seen as a dynamic continuum, then compound leaves can be seen as intermediate between simple leaves and whole shoots. Recent results in molecular genetics support this view. Phylogenetically, this could mean that compound leaves are the result of developmental hybridization, i.e. partial homeosis. Many other examples are given to illustrate the relevance and potential impact of basic conceptual and theoretical innovations in plant morphology.
... Tendrils share some developmental processes such as radial growth with typical stems (e.g. Gould and Cutter, 1986 ;Meicenheimer et al., 1983 ;Cote! et al., 1992 ;Gould et al., 1994). Therefore, it would be relevant to ask how the proteins of tendrils (such as those of peas) relate to those of stems. ...
... For example, some mutations in Pisum sativum leaves have been described as homeotic. The leaves of the afila strain bear tendrils at sites normally occupied by leaflets, whereas the leaves of the tendrilless strain bear leaflets at sites normally occupied by tendrils(GOULD et al. 1986). ...
The early ontogeny of the compound leaves and their associated stipules in Leea guineensis G. Don was studied using SEM. At initiation, the leaf primordium uses up most of the shoot apical meristem, which fluctuates greatly in size at different stages of development. Continuous meristematic regions at the base of the leaf primordium, later recognized as stipules, grow around and enclose the apical meristem. The continuity between the leaf, the stipules, and the shoot axis is striking at early stages of development, making it difficult to delimit these different structures. If growth processes such as timing and duration of growth and meristem fusion or extension are used to explain the vegetative morphology of L. guineensis, visualizing the relationship between the leaf, the stipules, and the shoot axis becomes easier.
... ofMeicenheimer et al. (1983) andFig. 9ofGould et al. (1986), perpendicular leaflet inception can be seen in young leaves of the garden pea and mutants. In contrast, figures byCGtC et al. (1992)show more or less radial leaflet and tendril primordia in conventional and semileafless peas. ...
The early development of the pinnately compound leaves in Murraya paniculata was studied using both epi-illumination and scanning electron microscopy as well as semithin plastic sectioning of the same specimens that were illustrated by means of epi-illumination. It is shown that morphological conclusions may be influenced by technical approaches such as the plane of sectioning. If the developing leaves are sectioned in the (median) sagittal plane, they appear to be rather different from stems and shoots. If, however, they are sectioned in the frontal plane, perpendicular to the sagittal plane, they appear more shoot-like in early development. Their apex could be described in terms of a tunica-corpus organization and the leaflet primordia are initiated like leaf primordia on a shoot tip with distichous phyllotaxy sensu lato. Subsequently, due to differential growth, reorientation of the leaflets occurs in one plane. Thus, the planar structure of the pinnate leaf is ontogenetically secondary. From a phylogenetic perspective, at least two conclusions are possible for plants with pinnate leaves such as those of Murraya: (i) if the ancestor of a pinnate taxon had simple leaves, the pinnate condition arose through homeosis, i.e., the expression of shoot features in leaf sites; (ii) if the ancestor of a pinnate taxon did not have simple leaves, the shoot-like early development of the pinnate leaves may indicate a common evolutionary basis of shoots and pinnate leaves in primitive branching systems. Since it is generally thought that the most primitive angiosperms have simple leaves, the homeotic hypothesis appears to be the preferred hypothesis for the origin of compound leaves in flowering plants. Key words: leaf development, comparative morphogenesis, shoot–leaf relationships, partial shoot theory of the leaf, homeosis.
... Several recent studies on leaf development (Dengler 1984;Gould et al. 1986;Jeune 1987;Meicenheimer et al. 1983; observations on young stages of leaf development in certain Vitis taxa (C. R. Lacroix and U. Posluszny, unpublished) confirm that differences between basic leaf shapes are visible at very early stages of development, especially with respect to pubescence and to the prominence of leaf lobe tips and leaf sinuses. ...
This study investigates the initiation of leaf shape in three taxa of Vitis from a quantitative point of view. Leaf characters, such as angles between major veins, ratios of the length of leaf lobes, of leaf lobes and sinuses, and of petioles and leaf lobes, were measured on leaves of different sizes and compared against leaf blade length (an indirect measure of developmental time) to see if there were differences between them at different developmental stages, and between taxa. Two trends were observed. Characters dealing with angles between major leaf veins, and those dealing with the ratio of the distance to the first point of branching of the major leaf vein of a lobe and the length of that leaf lobe, showed relatively little change over leaf blade length compared to more variable characters such as those involving the leaf petiole, leaf sinuses, or leaf lobes. If we assume that leaves of different lengths represent leaves at different stages of development, we can say that the characters dealing with angles or venation do not change extensively over time. However, characters dealing with ratios of the distance to a leaf sinus and lobe length, ratios of the length of two leaf lobes, or those dealing with the ratio of the length of the petiole and lobe length showed a stronger indication of change over leaf blade length. The parameters of interest in most of these ratios (petiole length or sinus depth compared against the length of a leaf lobe) varied more at different leaf blade lengths. It was also possible to distinguish between taxa for characters dealing with leaf lobes, petioles, and sinuses. Key words: morphometry, leaves, Vitis, development, characters, shape.
... The principal approach being pursued for the genetic dissection of processes that control leaf formation in P. sativum consists of characterization of relative morphology, anatomy and gene expression in leaves at different stages of development, in leaf morphology affecting recessive loss-of-function mutants and corresponding wildtypes [18,20,22,23,[28][29][30]40]. Concordantly, spontaneous and leaf morphology mutants have been detected/are being searched in land races, segregating populations of wide crosses and mutagenized populations [5,[11][12][13][14][15][16][17]19,21,24,27,36,38,40]. ...
The wild type compound leaf-blade of Pisum sativum has one to three pairs of simple leaflet pinnae in its petiole proximal domain, one to four pairs of simple tendril pinnae in the distal domain and a simple tendril pinna in the apical domain. A novel ethyl methane sulfonate induced dominant mutant was isolated and characterized whose leaf-blades formed MULTIFOLIATE PINNA pairs in the distal domain. The distal multifoliate pinnae or compound pinna-blades had three tendrilled-leaflets as pinnules. The pinnules had a bifacial elliptic-lanceolate leaflet body and arc shaped apex that mimicked the ringlet shaped apex of tendrils. The TL/tl, mfp/mfp and tl/tl, mfp/mfp leaf-blades also produced multifoliate (compound) pinna-blades in distal positions; the pinnules of these genotypes had elliptic shape. The pinnae were branched tendrils in TL/TL, MFP/mfp plants. The leaf-blade rachis was more ramified in af mfp double mutants than in af mutant. In the af mfp double mutant, the multifoliate pinna-blades were present on tertiary and secondary branches of the rachis in the proximal domain and on secondary branches and the primary rachis in the distal domain. The leaf-blades of the af tl mfp triple mutant genotype were an order of magnitude more ramified than those of af tl and af mfp genotypes in proximal as well as distal domains. The leaf-blade phenotypes of various genotypes revealed in this study and those known from previous work have allowed the following conclusions about the nature of mfp mutation and mfp function(s). (a) The presence of mfp mutation or mfp function changes the identity of distal primordia, from tendrils in the wildtype (MFP/MFP) leaf-blades to multifoliate pinna-blades in mfp/mfp mutant. (b) A pathway for the lamination of pinnules of multifoliate blades formed in distal and terminal domains in the mfp mutant and all domains in af mfp double mutant is activated by the mfp mutation. (c) The leaflet-/pinnule-lamination pathway activated by the tl mutation interacts with the mfp-directed pathway. (d) The mfp mutation intensifies rachis ramification in proximal and distal domains activated by the af mutation. This process is distinct from analogous rachis ramification that occurs in the af tl double mutant.
... Pairs of bars indicated by horizontal lines above them were analyzed by Student ' s t -test; N. S. = P > 0.05, * P < 0.05, ** P < 0.02. ( Meicenheimer et al., 1983 ;Gould et al., 1986 ;DeMason, 1997 , 2000 ), the additional pinna pairs produced on GA-treated uni-tac leaves are formed as the result of a longer period of tip-directed morphogenesis and reduced determinacy. Our gene expression experiments support this interpretation because GA upregulates UNI mRNA in unitac shoot tips. ...
Leaf morphogenesis, including that of compound leaves, provides the basis for the great diversity of leaf form among higher plants. Leaf form is an important character by which plants adapt to their environment. The common garden pea provides a developmental model system for understanding leaf development in the legumes and a contrasting one for other groups of plants.
We used genetic, tissue culture, and physiological methods, as well as DR5::GUS expression and qRT-PCR, to explore the interactions between the hormones gibberellic acid (GA) and auxin and Unifoliata ( UNI ) gene expression that control leaf morphogenesis in pea.
Rate of increase in leaf complexity during shoot ontogeny (i.e., heteroblasty) and adult leaf complexity are controlled by GA through UNI . Leaves on greenhouse-grown uni-tac mutants are rescued by weekly GA or auxin applications. Auxin responsiveness is reduced in uni-tac shoot and root tips and in wild-type shoot tips treated with auxin transport inhibitors. GA and auxin increase UNI mRNA levels in uni-tac as well as that of other transcription factors.
GA and auxin positively promote leaf dissection during leaf morphogenesis in pea by prolonging the time during which acropetally initiated pinna pairs are produced. GA-generated elaboration of leaf morphogenesis is in distinct contrast to that in other species, such as tomato and Cardamine . Instead, GA and auxin play common and supportive roles in pea leaf morphogenesis as they do in many other aspects of plant development
... Gould and Cutter (1985) defined the plastochron age of a leaf primodium as the number of visible leaf primodia initiated on the shoot meristem after its own initiation plus one. Gould and Cutter (1985) gave a leaf primodium an arbitrary plastochron value depending on its relative size. All of these methods are either complicated or involve damaging the plant. ...
The plastochron index (PI) is a measure of plant growth reports our findings on PI using the average length of and can be used to determine growth rate, based upon the first pair of leaflets on each node. Early leaflet appearance of successive leaves on the axis of the growth in peas occurs exponentially and the early plant. PI should under ideal growth conditions be a stages of growth of successive pairs of leaflets occur at regular event and should be predictable with a relatively the same relative growth rate. Given that growth of small error of a few hours. PI has been variously leaflets during early development can be measured calculated in peas, and each method reported has had successfully, we propose the use of leaflet growth as a with it a number of problems that do not allow for measure of the plastochron index in peas. Our results reasonable prediction of PI. Internode length varies suggest that plant age is best expressed using the greatly and is dependent upon the variety, which may be plastochron index, which is a measure of the time short- or long-stemmed; thus this parameter is not ideal interval between the initiations of successive events — for determining growth rate or plant age. This paper in the case of peas, of successive pairs of leaflets.
Pea leaf determination was examined by culturing excised leaf, leaflet, and tendril primordia of different ages on a nutrient medium. Pinna primordia were designated as 1) determined, if they grew normally in culture; 2) undetermined, if they grew into differentiated structures that were morphologically and anatomically different from either leaflet or tendril; or 3) partially determined, if the two pinnae of an opposite pair developed unequally in isolation, or for leaflet pinnae only, if laminae were initiated but did not develop completely. The compound pea leaf as a whole is determined over four plastochrons of development. Proximal pinnae are determined during the second leaf plastochron, approximately 0.8 plastochron after their initiation. The second most proximal pair of pinnae is determined during the third plastochron, and the terminal portion of the rachis is determined last, during the fourth plastochron. Determination of leaflet dorsiventrality is gradual, requiring a critical minimum period with the leaf in physiological contact with the shoot system. The rachis primordium, when isolated from the shoot, does not affect determination of its pinnae as leaflets or tendrils. Afila and tendril-less homeotic mutations do not alter the timing of pinna determination.
The mature wild type petals of Clarkia tembloriensis consist of a long slender claw and an expanded deltoid-shaped limb. They are pink, with a maroon spot at the base of the limb. Their surface texture is smooth. A variant of petal form, crinkled petal, occurs commonly in several natural populations of C. tembloriensis. The mature crinkled petals are elongated, greenish pink, and possess trichomes. They resemble the mature sepals of C. tembloriensis in general shape, color, and surface texture. Organ initiation and subsequent patterns of development of wild type petals, wild type sepals, and crinkled petals were examined and compared using scanning electron microscopy and allometric growth analysis. Crinkled petals are similar to wild type petals in time and position of primordia initiation, and in size and shape at inception. Crinkled petals are similar to wild type sepals in pattern of allometric growth. The crinkled petal mutant fits the broad definition of a homeotic mutant in that the petal has assumed characteristics of the sepal.
The early ontogeny of the pinnately, palmately, and ternately compound leaves in the Lardizabalaceae was studied by SEM. The leaf primordium of each of the three leaf types emerges as an identical short protrusion on the shoot apex; the leaf primordium produces the first leaflet initials laterally on its margin. Successive acropetal growth of the leaf axis and the following inception of the leaflet primordia are responsible for the pinnately compound leaf, whereas short basipetal growth accompanied with initiation of two or more pairs of leaflet initials results in a palmately compound leaf. If no elongation of the leaf axis nor additional inception of leaflet primordia occur during early ontogeny, a ternate leaf ensues.
According to a broad definition, homeosis is the assumption by one part of an organism of likeness to another part. In developmental terms this means that at the site of one part another part or features of another part are expressed. Whereas homeosis continues to be actively investigated in animals, especially at the genetic level, it has been almost completely ignored or overlooked in plants. One purpose of this article is to draw attention to the fact that homeosis is widespread in plants from the cellular to the organismal level. Another purpose is to examine some of the consequences of this phenomenon for developmental and evolutionary plant biology, particularly homology, punctuated equilibra, and macroevolution.
The effects of plant form and emergence time on size hierarchy formation in populations of two morphologically and genetically distinct varieties of peas (leafless and leafed) were studied. There were no significant differences in germinability between the two varieties, although leafless peas imbibed more rapidly than the leafed ones did. Monocultures of leafed and leafless peas were established at two densities: plants grown alone in small pots and plants grown at 576 m -. Time emergence was noted, and plant shape, biomass and seed production were measured at two-week intervals for ten weeks. Seedlings emerged continually over an eight-day period, and two cohorts of seedlings were distinguished (seedlings emerging 6–7 days after planting, and seedlings emerging > 7 days after planting). Dominance and suppression were observed in the high-density populations, and early-emerging plants had less hierarchical biomass distributions than did late-emerging ones. Although leafless peas were larger and suffered less mortality than leafed ones did at identical densities, there were no differences in the degree of size inequality between the two genotypes (emergence cohorts pooled), or within emergence cohorts between genotypes. The degree of size inequality increased with time among dominant individuals and decreased with time among suppressed individuals. These results broadly support Weiner and Thomas's (1986) hypothesis that plant form may affect the extent but not the existence of competitive asymmetry in plant populations.
Inflorescence ontogeny and morphology of the det mutant of Pisum sativum L. were investigated using scanning electron microscopy. This mutation causes the production of a limited number of axillary flowers followed by the formation of an apparent terminal flower slightly offset from the vertical. Our study indicates that the apparent terminal flower arises from an axillary meristem. The terminal meristem senesces and differentiates hairs, forming a rudimentary stub in the same manner as axillary meristems of conventional (Det) and det plants. Thus the dramatic effect of the det gene on inflorescence architecture results from early apical arrest rather than conversion of the terminal meristem to a flower as implied by the symbol det. This mutant will be valuable in elucidating regulation of apical arrest.
An kritischen Auseinandersetzungen mit der Pflanzenmorphologie ist kein Mangel (SATTLER 1986; RUTISHAUSER u. SATTLER 1986; MEEUSE 1986). MEEUSE (1986) sieht zwar in seiner “Anatomy of Morphology” das Konzept der Urpflanzen im Sinne von TROLL als “an abhorrence in a science supposed to be more or less exact”, doch sei eine moderne Form des Bauplan- (Typus-) Prinzips sehr viel rationaler als SATTLERS Formenkontinuum. SATTLER (1986) streitet in seiner “Biophilosophy” der “klassischen Cormuslehre” den Erfolg nicht ab, doch plädiert er für komplementäre Betrachtungsweisen, wie z.B. seiner “Continuum-Lehre” oder auch der von RUTISHAUSER (1986) ebenfalls für fruchtbar gehaltenen “Phytonlehre”. In Fallstudien wie z.B. Acacia longipedunculata, galioiden Rubiaceen, Hydrothrix gardeneri oder den Utricularia- Arten u.a. wird gezeigt, daß man mit dem Blattbegriff in erhebliche Schwierigkeiten kommt (SATTLER 1986: 101 ff; SATTLER u. RUTISHAUSER 1986; vgl. aber auch KAPLAN 1984). Dies ist richtig, doch sind die angeführten Fallstudien nicht wirklich klar. Die “Cormuslehre” wird von SATTLER (1986: 102) als die klassische mor-phologische Theorie ausgegeben. Die sogenannten Grundorgane können bei der Mehrzahl aller höheren Pflanzen beschrieben werden. Sie bilden un-abhängig von ihrer Form ein Gefügesystem (Typus), in dem sie durch ihre Lagebeziehungen zueinander definiert, d.h. homolog gesetzt werden können.
Leaves, the plant organs responsible for capturing and converting most of the 170 billion metric tons of carbon fixed globally each year, can be broadly grouped into two morphological categories— that is, simple and compound. Although simple-leaved species, such as corn and Arabidopsis, have traditionally been favored as model systems for studying leaf development, recent years have seen an increase in the genetic and molecular studies of compound leaf development. Two compound-leaved species, in particular, have emerged as model systems: tomato and pea. A variety of mutations that alter leaf morphology in these species have been described in the chapter and analyses of these mutations have allowed the construction of testable models of leaf development. In addition to the recent genetic and molecular analyses of tomato and pea, insight into the nature of compound leaf development may be gained through the study of: (a) the heteroblasty and heterophylly phenomena, in which a range of leaf forms can be produced, by a single shoot and (b) the evolutionary origins of compound leaves.
A number of single-gene, recessive mutations have been described in Pisum sativum L. that alter the form of the normal pinnately compound leaf and that show promise in elucidating genetic mechanisms of leaf development. Two recessive mutant alleles are known for the Unifoliata gene (the putative Lfy/Flo orthologue): uni and uni-tac (tendrilled acacia). To better understand the role of Uni in pea, we made observations on shoot development, leaf development, and in situ expression of Uni mRNA in these two mutants in comparison to wild-type plants. Although uni plants have abnormal, sterile flowers, those of uni-tac are usually normal and fertile. The uni and uni-tac plants produce more leaves and flower later than wild type, especially under long days. Some shoot features that are altered under long days are unaffected in uni plants, indicating that Uni may play a role in some photoperiodic responses. Adult uni leaves exceed one lateral leaflet pair only under short days, whereas uni-tac leaves typically possess two to three lateral leaflet pairs and one lateral tendril pair. Fusions between the ultimate lateral pinnae and the terminal leaflet are common in both mutants. Pinnae are initiated in an acropetal sequence over five plastochrons (P) for wild type, four for uni-tac, and three for uni. Lateral leaflet initiation and expansion occur earlier on wild-type leaves than on the mutants. Uni mRNA is expressed in the tips of juvenile leaf primordia through P4 in wild type, through P3 in uni-tac, and through P2 in uni. Ectopic expression also occurs in the shoot apical meristem of the mutants. We conclude that the Uni gene affects leaf development in pea by prolonging leaf tip growth and the period of pinna initiation and by delaying leaf tip differentiation. Therefore, it allows larger and more complex leaves to be produced by altering the timing of developmental events.
Three well-defined genes affect the morphological and anatomical features of the pea (Pisum sativum) compound leaf. Either singly or in combination, they specify five distinct pinna types. Using simple genetics, classical criteria for establishing homology, SEM of leaf development, and pinna histology, the phenotypes of the afila (af), tendril-less (tl), and tendrilled acacia (uni-tac)/unifoliata (uni) mutants are compared with that of wild-type plants, and the roles of the Af, Tl, and Uni genes are deduced. Marx's concept of inherent regions within the pea leaf is upheld. The leaf blade consists of three genetically/developmentally determined regions: proximal, distal, and terminal. All three genes modify leaf blade form by altering the timing of events during leaf development. In addition, these genes affect most aspects of leaf morphology (pinna pair number, pinna, petiole and leaf lengths, pinna branching) and histology (cell arrangement and size) as well as characteristics of shoot ontogeny (number of leaves, first node to flower, leaf heteroblasty).
Pea (Pisum sativum L.) plantlets with the afila (af) allele, alone or in combination with other leaf form mutations, were grown on media containing the auxin transport inhibitors 2,3,5,-triiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA), or the weak auxin p-chlorophenoxyisobutyric acid (PCIB). The morphology of the resulting plantlets was analyzed, and shoot tips were fixed for SEM observations and were frozen to monitor Uni gene expression using semiquantitative RT-PCR. Auxin transport was measured in leaf parts of two genotypes using 14C-labeled IAA. All three inhibitors produced similar morphological abnormalities in the four af genotypes used in this study, and the number and severity of abnormalities increased at the higher inhibitor concentrations. The number of pinna pairs produced on leaves was reduced. The proximal compound pinnae had fewer secondary branches and/or congenitally fused margins. Some leaves were converted from pinnately to palmately compound or to simple forms. Others were converted to scale leaves, or the leaf blades were lost, leaving only a pair of stipules. Various terminal pinna conversions occurred. Polar IAA transport was basipetal for all leaf parts and was greater in the petioles of af than wild type. Uni expression was reduced in shoot tips of plantlets grown in 60 μM NPA and TIBA and in the af uni-tac and af tl uni-tac genotypes. These results indicate that both an auxin gradient and the Uni gene play fundamental roles in controlling leaf morphogenesis, and specifically, in the compound pinnae of the af genotypes of pea.
When nodal segments of pea (Pisum sativum L.) are cultured in vitro, axillary shoots grow into miniature versions of their in situ homologues. Different organs on these shoots are miniaturized to diferent degrees. Leaf tendrils are most reduced in size; reproductive structures are least affected. Normal allometric relationships are maintained. Miniaturization is achieved primarily through a reduction in relative rate of elongation. Both cell size and cell numbers are reduced in the epidermis.
The partial-shoot theory of the leaf was a controversial hypothesis revived by Arber and supported by her morphological and
anatomical studies. This theory highlighted the parallels between leaves and shoots and contrasted with an alternative view
that leaves, with their limited growth potential, are completely distinct from shoots. Pea morphological mutants with altered
growth potential in their compound leaves are described. The unifoliata mutant has a limited growth potential relative to wild-type;cochleata, afila and insecatus have extended potentials. Characterization of theunifoliata mutation and gene expression patterns indicate that unifoliata is a common factor in pea compound leaf and floral shoot development, and so provides rudimentary support for the idea that
some leaves have shoot-like characteristics. Tomato leaves are also considered to lend tentative support. The afila and insecatus leaf forms are described as bipinnate and weakly bipinnate, respectively. These and the tendril-less mutant are potential phenocopies of legume relatives, an idea based on Vavilov's law of homologous series of variation. Arber
illustrated, but did not articulate in genetical terms, that morphological variation in structures within an individual plant
can be interpreted as reiteration of design. Analogous with Vavilov's view, this can be considered a consequence of the same
genetic programme in a different location.Copyright 2001 Annals of Botany Company
The translocation profiles of 11C-photoassimilates from either tendrils or leaflets of the compound leaf of Pisum sativum were similar in shape, speed and susceptibility to blockage by chilling and heat girdling. When the feed leaf component was
exposed to an anaerobic gas stream consisting of N2 gas supplemented with 40 Pa CO2, the export of previously-fixed 11C-photoassimilates from both leaflets and tendrils continued in the light, but stopped in the dark. However, in the light,
translocation of 11C-assimilates from the leaflet was rapidly blocked by a flow of pure N2 (i.e. anoxia). Movement of 11C-assimilates from the leaf of another C3 plant, sunflower, was similar to that from the pea leaflet. In contrast to both laminar leaf components, export from the
tendrils was stopped under pure N2 only in the dark. Taken together the data suggest that photosynthetic O2 production facilitated the movement of 11C-assimilates in the absence of exogenous O2. The differences observed between the tendrils and the leaflets exposed to pure N2 could be attributed to the greater capacity of tendrils to produce and recycle CO2 to support photosynthetic O2 production in the light.
The leaf blade of Pisum sativum L. possesses proximal leaflets and distal tendrils and is altered by two recessive mutations that affect pinna identity, afila (af) and acacia/tendrilless (tl). Using morphological and histology features we characterized the variation in leaf form and pinna anatomy of the Af and Tl heterozygous genotypes. Our goal was to identify the specific interactions of these genes and the relative influence of each in regulating all structural components of the leaf and pinna phenotypes. The Tl/tl genotypes possess broad tendril - narrow leaflets in the distal region that are histologically more similar to leaflets than to tendrils. The afafTltl leaves have simple tendrils in the distal region and branching complexity that is intermediate between that of aftl and af leaves in the proximal region. Only the most distal tips are slightly expanded. Because the Af and Tl genes interact to affect almost all aspects of leaf and pinna form, they affect development at multiple levels of organization.Key words: acacia, afila, Fabaceae, leaf morphology, leaf anatomy, Pisum sativum.
Respiratory changes during development, as well as growth and maintenance coefficients, were measured in organs of a typical compound leaf at the seventh node position of a pea (Pisum sativum) plant. The leaf consists of both laminar (leaflets and stipules) and cylindrical organs (tendrils, rachis, and petiole). Young tissue of each organ had relatively high respiration rates that declined as the tissue expanded. The respiration rates of leaflet, stipule, and tendril tissue throughout maturation were significantly greater than those of the other organs. The growth respiration coefficients were not significantly different among laminar and cylindrical organs. Maintenance respiration, expressed on a total dry mass basis and on a carbohydrate-corrected dry mass basis, as well as in vitro photosynthetic rates, were significantly lower in petioles and rachises than in tendrils or the leaflets and stipules. No difference in maintenance respiration of organs was observed when rates were expressed on a protein basis. A linear relationship between mass-based respiration and organ protein concentration was observed, suggesting that the energy costs involved in protein turnover may account, in part, for the differences in maintenance respiration among the organs. Taken together, our data show that although the tendril is structurally similar to the rachis, petioles, and stem, which have a role in supporting the canopy of this climbing plant, the respiratory properties of tendrils are more like those of leaflets and stipules, thus parallelling the photosynthetic characteristics of these organs in the compound leaf. Keywords: development, leaflets, Pisum sativum, respiration, stipules, tendrils.
We describe and compare leaf development in juvenile and adult shoots of Pseudopanax crassifolius, a strongly heteroblastic tree native to New Zealand. The shoot apical meristem is significantly larger in adult plants than in juvenile plants. Leaf primordia of the two forms are morphologically comparable at inception. The allometry of leaf length and width is similar in both forms up to a length of 7 mm. However, a shape index based on the relative position of maximum leaf width indicates that their morphology diverges when leaf primordia are 300 μm long. Laminae are initiated when the leaf primordium is shorter in adult shoots than in juvenile shoots. Maturation processes of the two leaf forms are similar. Cells and tissue types expand and differentiate in an acropetal direction. When leaf length, expressed as a proportion of mature leaf length, is used as a developmental index, the timing of all stages of leaf differentiation is comparable for the two leaf forms. The juvenile form is considered to be derived from the adult form by accelerated growth of the primordial leaf axis. Key words: Pseudopanax crassifolius, heteroblasty, leaf shape, development, allometry, New Zealand.
A modified mathematical model based on the concept of generative centers is proposed to describe organogenesis in young leaf primordia of Murraya paniculata. Measurements of specific parameters on leaf primordia at different stages of development support the basic assumptions of the model. These assumptions are exponential elongation and widening of primordia in the organogenetic phase and rhythmic production of lateral elements at a fixed distance from the apex of the developing primordium. In general, the model provides good estimates for growth parameters such as elemental growth rates. It also provides a relatively accurate description of the shape of the primordium during the organogenesis of lateral elements or leaflet primordia. Key words: leaf development, mathematical model, organogenesis, compound leaf, Murraya paniculata.
Comparative leaf development of conventional (cv. Improved Laxton's Progress) and semileafless (cv. Curly) peas was studied three-dimensionally, from initiation to maturity. The pattern of initiation of leaf primordia, stipules, and the pairs of lateral leaflet and tendril primordia is the same for both cultivars. However, their respective developmental pathways diverge by the time four pairs of lateral primordia have formed. In the conventional cultivar, the basal lateral primordia become increasingly dorsiventral as they develop into leaflets. Distal lateral primordia retain a cylindrical form and develop into tendrils. In contrast, basal first-order lateral primordia of the semileafless cultivar retain a cylindrical form and initiate second-order primordia, first in pairs, then in an alternate pattern. These second-order primordia develop into tendrils. Distal lateral primordium initiation and development are the same in both cultivars. Macroscopic development was subdivided into three stages based on tendril function. Stage I is an elongation phase during which the coiling response is not yet exhibited. During stage II, the tendrils are thigmotropic and retain their capacity to elongate. By stage III the tendrils have completed coiling and they no longer respond to thigmotropic stimuli. Stage I lasts an average of 1.4 ± 0.1 days in 'Improved Laxton's Progress' and 2.1 ± 0.1 days in 'Curly' from emergence from the stipule. Stage II may last up to 8 days, with an average of 6.4 ± 0.2 and 6.9 ± 0.3 days for 'Improved Laxton's Progress' and 'Curly', respectively, under greenhouse conditions for both cultivars. Key words: peas, Pisum sativum, leaf development, tendrils, afila.
We have examined the long-standing hypothesis that leaves are morphologically more complex following prolonged proximity to the shoot apical meristem. Growth rates of the petiole and rachis of conventional and mutant pea leaves were compared for successive nodes of insertion in seedling plants. Leaves were longer at higher nodes, though the relative growth rate did not vary. Mature afila leaves were longer than those of conventional and tendril-less genotypes. The afila leaf alone exhibited a transient, highly significant rise in relative growth rate during the plastochron interval P4.5–P5.5. This rise occurred after the stage at which leaves of the different genotypes were anatomically distinguishable (stage P2–P3). Rates of vertical displacement of the leaf primordium from the shoot apical meristem did not differ significantly among genotypes. Our data suggest that the rate of leaf extension is one of the consequences, rather than a cause, of leaf morphology.
Numbers of buds within a leaf axil and of leaf primordia within a bud varied with node of insertion, both in intact pea (Pisum sativum) seedlings and in cultured axillary shoots. Normally one or more nodes bore no visible buds. At the higher nodes naked buds and aberrant forms were observed. Shoots dissected from the embryo bore five or six leaf primordia and buds were present at the cotyledonary node and at three nodes immediately above. Benzylaminopurine in the nutrient medium promoted vegetative growth of cultured shoots. The height and extent of proliferation of cultured shoots varied both with the parental node from which explants were derived and with benzylaminopurine concentration. Results are discussed in relation to correlative inhibition.
The leguminous flora of Delhi comprises 78 Papilionoideae, 24 Caesalpinioideae and 24 Mimosoideae species; 80 of them are perennials. Five types of imparipinnate and two types of paripinnate compound leaves was observed on the species. The paripinnate leaves are bipinnate in 25 species (mostly mimosoid) and bifoliate in two species. The imparipinnate leaves were trifoliate or multifoliate in 59 papilionoid species and multifoliate in 16 caesalpinioid species; four of the papilionoid species produced leafletted and tendrilled unipinnate leaves. Leaves were bifacially simple in 22 species, simple with ectopic terminal growth in one species and simple tendril in one species. Twenty-one species (mostly mimosoid) were devoid of stipules. In 82 species stipules were small and free. Stipules were large and lobed in 17 species and large and adnate in four species. Two species of Caesalpinioideae produce compound leaf-like stipules. All four stipule phenotypes of 126 species corresponded with stipular phenotypes observed in wild type, coch, st and coch st genotypes of the model legume P. sativum. The seven leaf phenotypes observed in 126 species corresponded with phenotypes expected among combinations of uni (uni-tac), af, ins, mfp and tl mutants of P. sativum and sgl1, cfl1, slm1 and palm1 mutants of M. truncatula, also an IRL model legume. All the variation in leaf and stipule morphologies observed in the leguminous flora of Delhi could be explained in terms of the gene regulatory networks already revealed in P. sativum and M. truncatula. It is hypothesized that the ancestral gene regulatory networks for leaves and stipules produced in Leguminosae were like that prevalent in P. sativum.
Pea (Pisum sativum) has been an important model plant for several generations of plant physiologists, geneticists and developmental biologists. There exists an extensive body of knowledge on the genetics of many developmental processes including gibberellic acid (GA) biosynthesis and GA and auxin interactions during stem elongation. Auxin is a morphogen and is transported from cell to cell via vesicle-mediated secretion from sites of synthesis. This creates auxin concentration gradients, which can regulate genes controlling morphogenesis. Among the genes regulated are those of GA biosynthesis and this subsequently sets up secondary, parallel gradients of GA concentration. Both these hormones have been proposed to play roles during leaf development in other plant species. The question posed is whether auxin/GA interactions control leaf morphogenesis in pea. It was addressed by (1) looking at effects of auxin and GA inhibitors on leaf development, (2) attempting to rescue leaf form mutants by hormone application and (3) looking for genes expressed during leaf development that might be regulated by auxin and GA. Auxin and GA inhibitors produce common abnormalities during pea leaf development of wildtype (WT) cultured plantlets, which include: inhibition of leaf initiation, reductions in the number of pinna pairs produced and conversion of terminal tendrils into leaflets. Both GA and auxin rescued the tendrilled acacia (uni-tac) mutant by (1) increasing the number of pinna pairs produced and (2) converting terminal leaflets into tendrils. The Uni gene was transcriptionally up-regulated by auxin in shoot tips of cultured WT plantlets. Stable mRNA levels of three genes (PsPIN1, LE and IAA 4/5) known to be auxin-regulated also increased. These results suggest that both auxin and GA are involved in leaf initiation, promote leaf tip growth, and function in gradients and at multiple levels during pea leaf morphogenesis.
Isogenic lines of pea (Pisum sativum L.) with the genetically determined changes in leaf morphology, afila (af) and tendril-less (tl), were used to study the relationship between shoot and root growth rates. The time-course of shoot and root growth was followed
during the pre-floral period in the intact plants grown under similar conditions. The af mutation produced afila leaves without leaflets, whereas in the case of the tl mutations, tendrils were substituted with leaflets, and acacia-like leaves were developed. Due to the changes in leaf morphology
caused by these mutations, pea genotypes differed in leaf area: starting from day 7, the leaf area was lower in the af plants and larger in the tl plants as compared to the wild-type plants. Such divergence was amplified in the course of plant development and reached
its maximum immediately before the transition to flowering. Plants of isogenic lines did not notably differ in stem surface
areas. In spite of significant difference in total leaf area, the wild type and tl plants did not differ in leaf dry weight. Starting from leaf 9, the af plants lagged behind two leaflet-bearing genotypes (wild type and tl) in leaf dry weight, whereas stem dry weight was similar in the wild type and tl forms and slightly lower in the af plants. Root dry weights were practically similar in the wild type and tl plants until flowering. The reduction of leaf area in the af plants drastically reduced root dry weight. In other words, the latter index was related to the total weight and total area
of leaves and stems. The correlation analysis demonstrated an extremely low relationship between leaf and stem area and dry
weight and those of roots early in plant development (when plants develop five to seven leaves). Later, immediately before
flowering (nine to eleven leaves), root weight was positively related to leaf weight and area; however, stem area and root
weight did not correlate. Thus, in three genotypes (wild type, af, and tl), at the end of their vegetative growth phase, leaf and root biomass accumulated in proportion, independently of leaf area
expansion.
The comparative study of shoot and root growth was carried out, and the level of ABA therein determined in the mutant af and tl and wild-type isogenic lines of pea. The recessive af mutation transformed the leaflets into tendrils, and the tl mutation transformed the tendrils into leaflets. These mutations did not affect the length and number of internodes. In all
plants, the level of ABA in the leaves was 3–10 times greater than in the roots, and in the course of vegetative growth it
rose in both organs. An increase in the shoot area of tl mutant did not change the dry weight of underground and above-ground parts; therefore, the ratio shoot/root in the mutant
was identical to that in the wild-type plants. The maintenance of shoot dry weight in the tl mutant at the level of wild-type plant while its area considerably increased was accounted for by a decrease in the thickness
of the leaflet and stipule blades. The level of ABA in the stipules of mutant plants was greater than in the wild-type plants.
A decrease in the shoot area in the af mutant brought about a decline in its dry weight; however, the ratio root/shoot was maintained at the wild-type level due
to a reduced accumulation of dry weight by the root. The level of ABA in the roots of the af mutant was twice greater than in the leafy forms. ABA was assumed to participate in the control over the root growth exerted
by the shoot. The absence of leaflets in the af plants was partially compensated for by expanding stipules. The level of ABA therein was three times higher than in the plants
of wild type and comparable with the level in the leaflets of the tl mutant and in the wild-type plants. The role of ABA in the growth and final size of leaf blades is discussed.
Shoot-like compound leaves are ancient and predate the evolutionary origin of whorled flowers. By studying leaves of this type it may be possible to gain further insight into similar fundamental processes in plant development. Here, we describe the pea compound leaf from the viewpoint that considers it as a determinate lateral shoot. By integrating research on developmental mutants, we present a model of the genetic control of patterning in the pea leaf.
The pea Pisum sativum genes AFILA (AF), TENDRIL-LESS (TL) and UNIFOLIATA (UNI) have been shown previously to be involved in the compound leaf blade patterning and AF and TL genes in leaf blade growth. Here, the interactions of the previously described UNI gene with AF and TL were studied using a new uni-tac allele and af and tl alleles, in the new background of cultivar Pusa Harbhajan. The leaf blades formed on the embryonic and mature pre- and post-flowering leaves from plants of AFTLUNI, afTLUNI, AFtlUNI, AFTLuni-tac, aftlUNI, afTLuni-tac, AFtluni-tac and aftluni-tac genotypes were measured for pinna growth in terms of their laminated and non-laminated organs. The investigation showed that UNI activates, and AF and TL repress the leaf blade ramification. UNI and AF act together in lamina-dominated pinna growth; we call this the AF-dependent leaflet development pathway. Presence of second AF-independent pathway for leaflet formation is described. TL and UNI are identified as antagonists of such pathway(s). UNI, AF and TL functions can up-regulate as well as down-regulate leaf-blade morphogenetic developmental events, in organ-specific manner.
In the Cucurbitaceae, the tendrils, coiling organs used for climbing and mechanical support, are part of an axillary bud complex (ABC). Although the morphological nature of tendrils and the branching pattern of the ABC in the Cucurbitaceae have been much studied, their homology remains unresolved, with hypothesized candidates being the leaf, flower, stem, or stem-leaf combination. We used Echinocystis lobata as a model to study the early ontogeny of the ABC with epi-illumination microscopy and serial resin sections. The ABC produces four structures (proximal to distal, relative to the subtending leaf) as the result of two successive subdivisions: an inflorescence of staminate flowers, a solitary pistillate flower, a lateral bud, and a tendril. The first separates the tendril primordium from the continuation of the ABC, and the second separates the staminate inflorescence and the ABC. The pistillate flower apparently forms between the staminate inflorescence and the lateral bud. Because there is no subtending leaf during these subdivisions and the first lateral appendages in the resulting primordia arise in the same plane, we conclude that the tendril and other organs formed by the ABC are lateral branches of equal morphological value. This study is the basis for continuing comparative and functional morphological studies.
In order to dissect the genetic regulation of leafblade morphogenesis, 16 genotypes of pea, constructed by combining the wild-type and mutant alleles of MFP, AF, TL and UNI genes, were quantitatively phenotyped. The morphological features of the three domains of leafblades of four genotypes, unknown earlier, were described. All the genotypes were found to differ in leafblade morphology. It was evident that MFP and TL functions acted as repressor of pinna ramification, in the distal domain. These functions, with and without interaction with UNI, also repressed the ramification of proximal pinnae in the absence of AF function. The expression of MFP and TL required UNI function. AF function was found to control leafblade architecture multifariously. The earlier identified role of AF as a repressor of UNI in the proximal domain was confirmed. Negative control of AF on the UNI-dependent pinna ramification in the distal domain was revealed. It was found that AF establishes a boundary between proximal and distal domains and activates formation of leaflet pinnae in the proximal domain.
A very simple algebraic model is proposed, which generates ‘leaves’ resembling both normal and mutant forms of the leaves of the pea (Pisum sativum L.). There are a number of simply inherited mutant forms of pea in which normal leaf structures (leaflets, tendrils, and rachides) occur in abnormal arrangements. For example, the acacia or tendril-less mutation (tl) causes leaflets to appear where the normal leaf has tendrils, and afila (af) replaces leaflets with branching rachides. The essential features of the model are, firstly, that the structure is determined sequentially during the repeated growth and sub-division of meristems, and secondly, that the developmental fate of each meristematic primordium is determined by its size: small primordia become tendrils, intermediate primordia leaflets and large ones rachides. It is proposed that the genes af andtl alter the size thresholds. The published descriptions of normal morphogenesis, of mutant phenotypes and of the effects of surgery are compatible with the model.
Explants from inflorescence stalks of Gladiolus when cultured in vitro regenerated new plantlets within 6-7 weeks. Regeneration was started by the formation on the basal end of a thin layer of callus and root primordia. This was followed by formation of buds and cormlets, on the distal end. The regeneration of the various organs from the explants was found to be polarized and depended on the levels of growth substances added to the basal medium, best combination for organ initiation being 10 ppm naphthalene-acetic acid and 0.5 ppm of kinetin.
Some easily seen structural features of living plant cells are destroyed or badly distorted by most of the common fixatives and embedding media used in plant histology. In stained sections of plant tissues fixed in FAA (formalin-acetic acid-alcohol mixtures) and embedded in paraffin wax, for example, mitochondria and fine transvacuolar strands of cytoplasm are usually not visible. Many structural features such as these can be preserved, however, with suitable fixatives and embedding media. Fixation in non-coagulant fixatives (e.g., osmium tetroxide, acrolein, glutaraldehyde, formaldehyde) and the use of plastics as embedding media is recommended. A method of fixation in acrolein and embedding in glycol methacrylate polymer is described in detail. In a wide range of plant specimens prepared in this way, stained sections 1-3 microns thick showed excellent preservation of tissue and cell structures. 39 references, 11 figures.
Vigorously growing calluses were obtained in Pisum sativum L. cvs. Puget and Upton (but not in cvs. Maro, Melton and Vedette) which have continuously regenerated shoots, over a period of nearly 3 years. The calluses were induced on the bases of plumules, excised from germinated seed, cultured on Murashige and Skoog (MS) medium supplemented with 1 mg 1−1 6-benzylaminopurine (BAP) and 4 and 8 mg 1−1 indole-butyric acid (IBA). Shoot regeneration took place 2–4 weeks after transfer to the same medium with IBA reduced to 0.25 mg 1−1 and has continued while the callus has been regularly subcultured to fresh media. Regenerated shoots could be propagated as shoot cultures and rooted on medium containing half-strength MS salts, 1.5% sucrose and 2 mg 1−1 indole-3-acetic acid (IAA). Plants regenerated during the first year of callus growth were diploid and mostly morphologically normal. Plants regenerated after 2 years show variable morphology as shoot cultures and are more difficult to root.
Meristem characteristics of normal, afila (af), acacia (tl), reduced stipule (st), and combinations of these leaf phenotypes were investigated in pea (Pisum sativum L.). The multiple tendrils of the afila leaf are formed from numerous secondary branches on the leaflet primordia. Adaxial and marginal meristems are absent in afila leaflets. The tendril-like morphology of the terminal and secondary branches of the afila leaflets is derived from a radial marginal meristem, which is characteristic of normal tendril development. The small terminal leaflet lamina on tendrils of the acacia leaf is produced by adaxial and marginal meristems which become apparent in the distal portion of the tendril late in leaf ontogeny. The reduced stipules of the reduced stipule leaf result from early loss of abaxial and adaxial stipule marginal meristems. Combinations of the af, tl, and st genes apparently have no modifying influences on their mutual expression with one exception; the aftlst mature reduced stipule is significantly wider than stipules in st, afst, and tlst phenotypes. The greater final width of triple recessive stipules is attributed to the persistence of the adaxial stipular marginal meristem in this phenotype.
Charlton for help with the sectioning, Mr. J. Hutton for help with the cryo-SEM work, and Mrs. J. Underwood for typing the manuscript. The work was funded by a Cooperative
- We
- Dr
We thank Dr. G. Hussey for demonstrating the in vitro tech-nique, Dr. W. A. Charlton for help with the sectioning, Mr. J. Hutton for help with the cryo-SEM work, and Mrs. J. Underwood for typing the manuscript. The work was funded by a Cooperative Award in Science and Engineering from the Science and Engineering Research Council to K. S. Gould. BATESON, W. 1894. Materials for the study of variation. Macmillan, London. CONOVER, W. J. 197 1. Practical nonparametric statistics. Wiley, New York.
Fixation, dehydration and embedding of bio-logical specimens. Practical methods in electron microscopyAfila" a new mutation in pea (Pisum sativum L.)
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GLAUERT, A. M. 1975. Fixation, dehydration and embedding of bio-logical specimens. Practical methods in electron microscopy. North Holland Publishing Co., Amsterdam, The Netherlands. GOLDENBERG, J. B. 1965. "Afila" a new mutation in pea (Pisum sativum L.). Bol. Genet. 1: 27 -31.
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A revised medium for rapid growth and bioassays with tobacco tissue cultures
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