Peter J. Davies

Cornell University | CU · Sections of Plant Biology & Horticulture, School of Plant Sciences

The hormonal control of whole plant senescence, as determined by the senescence of the apex, is being investigated using a genetic line-of peas (Pisum sativum L.). This line, designated G2, has dominant genes at two different loci, both of which function in short days to delay apical senescence and thus greatly extend the reproductive phase. GA 3 a...

The production of wine grapes in upstate New York (USA) is limited by diseases that are promoted by the cool and sometimes rainy climate. A breeding program has been introducing disease resistance from related species into the cultivated stock. Previous work has indicated that such resistance may be based on biochemical reactions rather than on a h...

This article comments on: McAdam EL, Reid JB, Foo E. 2018. Gibberellins promote nodule organogenesis but inhibit the infection stages of nodulation. Journal of Experimental Botany 69, 2117–2130.

During seed germination, sugars and auxin are produced from stored precursors or conjugates respectively, and transported to the seedling axis. To elucidate the mode of travel of indole-3-acetic acid (IAA) into the phloem, a solution of [3H]IAA, together with [14C]sucrose, was injected into the endosperm cavity harboring the cotyledons of germinati...

During seed germination sugars and auxin are produced from stored precursors or conjugates respectively and transported to the seedling axis. To elucidate the mode of travel of IAA into the phloem a solution of [3H]indoleacetic acid (IAA), together with [14C]sucrose, was injected in the endosperm cavity harboring the cotyledons of germinating seedl...

Despite the demonstrated importance of gibberellins (GAs) as regulators of fruit tree stature,information on their in vivometabolismin apple vegetative tissues is still lacking. To determinewhether theGAcontent andmetabolism differs between dwarf and standard phenotypes and the influence of rootstocks, [14C]GA12,a common precursor of all GAs in hig...

After the flowering of an annual plant, the whole plant will senesce and die. For the process to go to completion, this monocarpic senescence must include three coordinated processes, which have not previously been considered as a total syndrome: (1) the arrest of growth and senescence of the shoot apical meristem; (2) senescence of the leaves; and...

‘Empire’ apple fruit are more susceptible to flesh browning at 3.3°C if treated with 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. To better understand the metabolic changes associated with this browning, untargeted metabolic profiling with partial least squares analysis has been used to visualize changes in metabolic profile d...

Male plants of spinach (Spinacea oleracea L.) senesce following flowering. It has been suggested that nutrient drain by male flowers is insufficient to trigger senescence. The partitioning of radiolabelled photosynthate between vegetative and reproductive tissue was compared in male (staminate) versus female (pistillate) plants. After the start of...

Plant hormones are a group of naturally occurring, organic substances which influence physiological processes at low concentrations. The processes influenced consist mainly of growth, differentiation and development, though other processes, such as stomatal movement, may also be affected. Plant hormones1 have also been referred to as ‘phytohormones...

The way in which a plant hormone influences growth and development depends on: 1) The amount present: this is regulated by biosynthesis, degradation and conjugation. 2) The location of the hormone: this is affected by movement or transport. 3) The sensitivity (or responsiveness) of the tissue: this involves the presence of receptors and signal-tran...

Plant hormones play a crucial role in controlling the way in which plants grow and develop. While metabolism provides the power and building blocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate them to produce the form that we recognize as a plant. This book is a description of these natu...

Growth of the primary root of 12 genotypes of peas (Pisum sativum) differing in their stem height was recorded for 14 days. The growth rate of roots of wild-type tall, gibberellin (GA)-deficient le dwarf or slender mutants (with la crys) was similar (3 cm day−1); that of severely GA-deficient nana (na-1) plants was 50% of wild-type but elongation c...

Growth of the roots vertical roots of 12 genotypes of peas (Pisum sativum), which differed in stem height because of differing gibberellin (GA) or brassinosteroid content or signal transduction, was recorded during continuous exogenous applications of differing concentrations of indoleacetic acid (IAA) and GA3, over a period of 12 h with a sensitiv...

In fruit such as the tomato (Solanum lycopersicum), ethylene initiates ripening and senescence, whereas polyamines have been considered senescence inhibitors. Putrescine is elevated in long-keeping Alcobaca tomato (Dibble et al., 1988), and polyamine applications delay tomato ripening (Law et al., 1991).

Ethylene initiates the ripening and senescence of climacteric fruit, whereas polyamines have been considered as senescence inhibitors. Ethylene and polyamine biosynthetic pathways share S-adenosylmethionine as a common intermediate. The effects of 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, on ethylene and polyamine metabolis...

Tuber formation in potatoes (Solanum tuberosum L.) is a complex developmental process involving a number of important biological systems. Under conditions of a short-day photoperiod and cool temperature, a transmissible signal is activated that initiates cell division and expansion and a change in the orientation of cell growth in the subapical reg...

Efforts to breed for the ability to tuberize under long days or for the length of tuber dormancy should benefit not only from information on the location of genes associated with these traits, but also from an understanding of the hormones the genes control. Understanding the role of the respective genes is a logical step in developing the best bre...

TheAAIR genomic DNA of G2 pea (Pisum sativum L.) was amplified by PCR method. Sequence analysis showed that it was composed of 8 introns and 9 exons with three of the introns containing specific A/T-rich endogenous promoter regions. Molecular hybridization experiments revealed that the expression of AAIR remained at a high level before and after fl...

Potato (Solanum tuberosum) homeobox 1 (POTH1) is a class I homeobox gene isolated from an early-stage tuber cDNA library. The RNA expression pattern of POTH1, unlike that of most other class I knotted-like homeobox genes, is widespread in the cells of both indeterminate and differentiated tissues. Using in situ hybridization, POTH1 transcripts were...

The plant hormone concept probably derives from observations of morphogenic and developmental correlations by Sachs between 1880 and 1893. He suggested that “Morphological differences between plant organs are due to differences in their material composition” and postulated the existence of root-forming, flower forming and other substances that move...

Summary• The identities and concentrations of cytokinins in goldenrod ball galls, normal goldenrod stems, and in the gall-forming larvae of the tephritid fly Eurosta solidaginis were determined in order to gain insight into the mechanism of ball gall formation on Solidago altissima.• Zeatin, zeatin riboside, isopentenyladenine, and isopentenyladeno...

• Indole-3-acetic acid (IAA) concentrations are reported in ball galls, stem tissue, and in the gall-forming larvae of the tephritid fly Eurosta solidaginis, to gain insight into the mechanism of ball gall formation on the goldenrod, Solidago altissima.• IAA was identified and quantified by gas chromatography–mass spectrometry, with [13C6]-IAA as a...

DNA-based genetic markers are now widely used by geneticists to locate genes for quantitative traits, and may also serve as a valuable tool for dissecting complex physiological phenomena. Van den Berg et al. (1996a QTL analysis of potato tuberization. Theor Appl Gen 93: 307–316), using restriction fragment length polymorphism (RFLP)-mapped populati...

Many aspects of plant growth and development are regulated by hormones in a complex, interacting fashion, such that the level of or response to any single hormone cannot explain the phenomenon. The ability to map the multiple genes (Quantitative Trait Loci) influencing both development and hormonal levels enables the elucidation of both the extent...

While indole-3-butyric acid (IBA) has been confirmed to be an endogenous form of auxin in peas, and may occur in the shoot tip in a level higher than that of indole-3-acetic acid (IAA), the physiological significance of IBA in plants remains unclear. Recent evidence suggests that endogenous IAA may play an important role in controlling stem elongat...

The Le gene of pea encodes a gibberellin 3-hydroxylase. Heterologous expression of the le-2 allele indicated that a truncated protein was produced, confirming that le-2 is a null mutation. The Le expression product was unable to metabolise GA12, but was able to produce a small quantity of GA8 from GA29. The le-2 mutation had no effect on the levels...

In shoots of the garden pea (Pisum sativum L.), the main bioactive gibberellin (GA) is GA1, which is synthesised from GA20 by 3β-hydroxylation. Gibberellin A20 is produced from GA19, as part of the process known as GA 20-oxidation. Because these steps are thought to be negatively regulated by GA1, we compared the metabolism of labelled GA19 and GA2...

We cloned a developmentally regulated gene from a cDNA library constructed from short-day (SD) grown G2 pea tissue using cDNA representational difference analysis (cDNA RDA) and named it PPF-1 for the first Pisum sativum post-floral-specific gene. Sequence comparisons with various databases revealed that PPF-1 shares a substantial homology only at...

In previous studies polygene mapping of a backcross population derived from haploid potato (Solanum tuberosum) and a diploid wild species (Solanum berthaultii) showed at least eight quantitative trait loci (QTLs) associated with tuber dormancy. The same population was mapped for abscisic acid (ABA) content in tubers so that any QTLs identified coul...

We describe the isolation of the Le gene of pea, which controls internode elongation and originally was described by Mendel. Heterologous screening of a pea cDNA library yielded a partial clone that was 61% identical to coding regions of the putative Arabidopsis gibberellin 3 beta-hydroxylase gene, GA4. DNA gel blot analysis with this cDNA revealed...

Pea (Pisum sativum L.) lines G2 (dwarf) and NGB1769 (tall) (Sn Hr) produce flowers and fruit under long (LD) or short (SD) days, but senesce only under LD. Endogenous gibberellin (GA) levels were inversely correlated with photoperiod (over 9-18 h) and senescence: GA20 was 3-fold and GA1 was 10- to 11-fold higher in flowering SD G2 shoots, and the v...

The effects of GA on stem elongation were studied using segments from one tall and three dwarf light-grown pea genotypes varying in endogenous hormone content. Stem segments were cut at two distinct ages: when the fourth internode was at about 6-13% of full expansion (early-expansion) or at 18-25% of full expansion (mid-expansion). Light microscopy...

Tuberonic acid glucoside and tuberonic acid glucoside Me ester were detected in the leaves of Solanum tuberosum. This is the first report of the isolation of the latter from potatoes. Higher concentrations of both substances were detected in leaves of plants grown under long than under short days. Methylation of tuberonic acid glucoside prior to GC...

The objective of this investigation was to examine the response to exogenous auxin (indole-3-acetic acid; IAA)of stem segments at two developmental stages. The standard auxin response of excised stem segments and intact plants consists of an initial growth response and a prolonged growth response. We found that this biphasic response does not occur...

Exogenous gibberellin (GA) and auxin (indoleacetic acid [IAA]) strongly stimulated stem elongation in dwarf GA1-deficient le mutants of light-grown pea (Pisum sativum L.): IAA elicited a sharp increase in growth rate after 20 min followed by a slow decline; the GA response had a longer lag (3 h) and growth increased gradually with time. These respo...

Metabolism of [14C] gibberellin(GA)12-aldehyde and [14C]GA12 in vegetative tissue of potato (Solanum tuberosum ssp. andigena) was studied by supplying solutions of these compounds to the base of isolated shoot tips and analyzing the metabolic products by radiodetection after HPLC. Endogenous gibberellins that co-eluted with the 14C-metabolites on H...

Potato tuberization is promoted by short days and inhibited by applications of gibberellin (GA). Wildtype Solanum tuberosum ssp. andigena required short days for tuberization, whereas their dwarf siblings tuberized under long days. Nevertheless, shortening the photoperiod also enhanced tuberization of dwarf plants and caused an increase in leaf ang...

The concept of control by changing concentrations is crucial to the original concept of hormones in mammals. A few years ago, a great stir was created amongst biologists working with plant hormones by the suggestion of Trewavas (56) that there is no evidence that plant hormones act via changes in the amount or concentration of the hormone, and that...

Plant hormones play a crucial role in controlling the way in which plants growand develop. Whilemetabolism providesthepowerand buildingblocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, theyplayacontrolling role...

Exogenously applied indole-3-acetic acid (IAA) strongly promoted stem elongation over the long term in intact light-grown seedlings of both dwarf (cv Progress No. 9) and tall (cv Alaska) peas (Pisum sativum L.), with the relative promotion being far greater in dwarf plants. In dwarf seedlings, solutions of IAA (between 10-4 and 10-3 M), when contin...

The stem elongation responses of etiolated peas (Pisum sativum L.) to fluorescent light (35–45 mol.mt-2.s-1) were recorded using high resolution position transducers. Continuous fluorescent light decreased growth by 70% within 9 min. The growth rate declined to 5% of the control over the next 2 h and remained at this level for 7 h. Pulses of fluore...

Abstract— Phytochrome influences stem elongation and the mechanism for this is not understood. The levels of indole-3-acetic acid (IAA) were analyzed in an leLv genotype of Pisum sativum L. which responded to end-of-day far-red light by doubling growth rate. The IAA levels in epidermal peels increased 40% after far-red light whereas IAA levels of t...

The effect of red (R) and far-red (FR) light on stem elongation and indole-3-acetic acid (IAA) levels was examined in dwarf and tallPisum sativum L. seedlings. Red light reduced the extension-growth rate of etiolated seedlings by 70–90% after 3 h, and this inhibition was reversible by FR. Inhibition occurred throughout the growing zone. After 3 h o...

The effect of red (R) and far-red (FR) light on stem elongation and indole-3-acetic acid (IAA) levels was examined in dwarf and tall Pisum sativum L. seedlings. Red light reduced the extension-growth rate of etiolated seedlings by 70-90% after 3 h, and this inhibition was reversible by FR. Inhibition occurred throughout the growing zone. After 3 h...

Introduction Historical Background Source-Sink Relationships Mineral Nutrients Plant Hormones A Senescence Factor from Fruits? Carbohydrate Partitioning During Reproductive Development in Pea Photoassimilate Partitioning and Senescence in Spinach Plants Senescence in the Abscence of Flowers Conclusion Literature Cited

The exposure of dark-grown seedlings to light results in a dramatic decrease in the rate of stem elongation, which is one of the many facets of the phenomenon of de-etiolation. While the spectral characteristics of the response are now relatively well known the transduction chain between the reception of the light and the ultimate growth response i...

Ten mutants with modified sensitivity to applied gibberellins (GAs) have so far been characterised in peas. These range in length from very short(erectoides)types(e.g. lk;Reid, 1986) through to elongated types such as slender (caused by the polymeric gene combinationla crys;Pottset al., 1985). The sensitivity to applied GA1also varies from a minima...

Mature green tomato fruit (Lycopersicon esculentum Mill) of cv. Rutgers and the line Alcobaca-red were vacuum infiltrated with solutions of polyamines, their precursors and metabolites, and other compounds which might affect ripening and/or storage duration. Putrescine (1,4-diaminobutane), spermidine, spermine, diaminopropane, -aminobutyric acid an...

Metabolism of(14C)gibberellin (GA)A12(GA12) and(14C)gibber- ellin A12-aldehyde (GA12-aldehyde) wasexamined incotyledons andseedcoatsfromdeveloping seedsofpea(Pisum sativum L.). Bothweremetabolized toonly13-hydroxylated GAsincoty- ledons butto13-hydroxylated andnon-13-hydroxylated GAsin seedcoats. Themetabolism of(14C)GA12 wasslower inseed coatsthan...

Metabolism of [(14)C]gibberellin (GA) A(12) (GA(12)) and [(14)C]gibberellin A(12)-aldehyde (GA(12)-aldehyde) was examined in cotyledons and seed coats from developing seeds of pea (Pisum sativum L.). Both were metabolized to only 13-hydroxylated GAs in cotyledons but to 13-hydroxylated and non-13-hydroxylated GAs in seed coats. The metabolism of [(...

Metabolism of [C-14]gibberellin (GA) A12 (GA12) and [C-14]gibberellin A12-aldehyde (GA12-aldehyde) was examined in cotyledons and seed coats from developing seeds of pea (Pisum sativum L.). Both were metabolized to only 13-hydroxylated GAs in cotyledons but to 13-hydroxylated and non-13-hydroxylated GAs in seed coats. The metabolism of [C-14]GA12 w...

[3H]gibberellin A9 was applied to shoots or seed parts of G2 pea to produce radiolabeled metabolites. These were used as markers during purification for the recovery of endogenous GA9 and its naturally occurring metabolites. GA9 and its metabolites were purified by HPLC, derivatized and examined by GC-MS. Endogenous GA9, GA20, GA29 and GA51 were id...

The fruit of the Alcobaca landrace of tomato (Lycopersicon esculentum Mill.) have prolonged keeping qualities (determined by the allele a/c) and contain three times as much putrescine as the standard Rutgers variety (A/c) at the ripe stage (ARG Dibble, PJ Davies, MA Mutschler [1988] Plant Physiol 86: 338-340). Polyamine metabolism and biosynthesis...

The metabolism of [1,4-(14)C]putrescine and [terminal methylene-(3)H]spermidine was studied in the fruit pericarp (breaker stage) discs of tomato (Lycopersicon esculentum Mill.) cv Rutgers, and the metabolites identified by high performance liquid chromatography and gas chromatography-mass spectrometry. The metabolism of both putrescine and spermid...

Red light causes a reduction in the extension growth of dark-grown seedlings. The involvement of gibberellin in this process was tested by screening a number of gibberellin synthesis and gibberellin response mutants of Pisum sativum L. for the kinetic response of stem growth inhibition by red light. Gibberellin deficient dwarfs, produced by mutant...

Redlight causesareduction intheextension growth ofdark- grownseedlings. Theinvolvement ofgibberellin inthis process wastested byscreening anumberofgibberellin synthesis and gibberellin response mutants ofPisumsativum L.forthekinetic response ofstemgrowth inhibition byredlight. Gibberellin defi- cient dwarfs, produced bymutantalleles attheLe,Na,andL...

Free indole-3-acetic acid levels were measured by gas chromatography-mass spectrometry in three ultra-tall ;slender' Pisum sativum L. lines differing in gibberellin content. Measurements were made for apices and stem elongation zones of light-grown plants and values were compared with wild-type, dwarf, and nana phenotypes in which internode length...

Biophysical parameters related to gibberellin (GA)-dependent stem elongation were examined in dark-grown stem-length genotypes of Pisum sativum L. The rate of internode expansion in these genotypes is altered due to recessive mutations which affect either the endogenous levels of, or response to, GA. The GA deficient dwarf L181 (ls), two GA insensi...

The metabolism of (1,4-¹⁴C)putrescine and (terminal methylene-³H)spermidine was studied in the fruit pericarp (breaker stage) discs of tomato (Lycopersicon esculentum Mill.) cv Rutgers, and the metabolites identified by high performance liquid chromatography and gas chromatography-mass spectrometry. The metabolism of both putrescine and spermid...

To interpret the metabolism of radiolabeled gibberellins A(12)-aldehyde and A(12) in shoots of pea (Pisum sativum L.), the identity of the radiolabeled peaks has to be determined and the endogenous presence of the gibberellins demonstrated. High specific activity [(14)C]GA(12) and [(14)C]GA(12)-aldehyde were synthesized using a pumpkin endosperm en...

While gibberellin (GA) A12 and GA12-7-aldehyde have been well established as intermediates in GA biosynthesis, their presence in higher plants has not been conclusively demonstrated, with the exception of GA12-aldehyde in mature pea seeds. High specific activity [14C] GA12 and [14C]GA12-aldehyde were synthesized enzymatically from [4,5-14C]mevaloni...

The G2 line of peas (Pisum sativum L.) displays senescence and death of the apical bud only in long days and in the presence of fruit. As the removal of fruit prevents senescence, one possible mechanism by which fruits induce senescence is that the fruits produce some ;senescence factor' under long day conditions, which is then transported to the a...

In the G2 line of peas (Pisum sativum L.) senescence and death of the apical bud occurs only in long days (LD) in the presence of fruits. Removal of the fruits prevents apical senescence. One possible reason for the senescence-inducing effect of fruit is that the fruits produce a senescence-inducing factor which moves to the apical bud and is respo...

Pisum sativum L. fruits export a small quantity of radiolabeled substances to other plant parts after the fruits are allowed to photosynthesize in the presence of (14)CO(2). Export was uninhibited by peduncle girdling suggesting an apoplastic route for transport of material, presumably by ;reverse' flow in the peduncle xylem. To determine if any di...

Apical senescence but not flower initiation is delayed by short days (SD) compared to long days (LD) in pea plants (Pisum sativum L.) of genotype E Sn Hr. We recently reported that delay of senescence correlated with slower reproductive development, suggesting that fruits are weaker sinks for assimilates under delayed senescence conditions. Thus, w...

Fruit of tomato landrace Alcobaca, containing the recessive allele alc, ripen more slowly, with a reduced level of ethylene production, and have prolonged keeping qualities. The levels of polyamines in pericarp tissues of alc and ;wild type' Alc (cv Rutgers and Alcobaca-red) fruit were measured by HPLC in relation to ripening. Putrescine was the pr...

A simple, rapid, direct method for the HPLC analysis of 1-aminocyclopropane-1-carboxylic acid (ACC) as its o-phthaldialdehyde derivative is described. The method is sensitive to about 1 pmol and can be used on plant tissue extracts with no cleanup. It will prove valuable in plant extracts where the chemical conversion of ACC in the tissue extracts...

The commonly studied amines are the diamines, diaminopropane, cadaverine and putrescine, the triamine, spermidine and the tetraamine, spermine. Although the physiological role of polyamines remains unclear, they are considered important in the growth of plants, animals, and microorganisms (Bachrach 1973). The function and biochemistry of polyamines...

The idea that transport was an essential part of the role of plant hormones originally came from experiments on the phototropic control of coleoptile growth. The hypothesis was that the IAA was synthesized in the tip, transported basipetally and was then redistributed laterally to give differential growth and bending. We now know that most of the I...

Plant hormones playa crucial role in controlling the way in which plants grow and develop. While metabolism provides the power and building blocks for plant life it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, they playa controlling...

Experiments were designed to test the hypothesis that the labeled products recovered from plant tissue incubated with [(14)C]GA(12)-7-aldehyde ([(14)C]GA(12)ald) would serve as appropriate [(14)C]markers for the recovery of naturally-occurring gibberellins (GAs). The [(14)C]GA(12)ald (about 200 millicuries per millimole) was synthesized from pumpki...

In G2 peas (Pisum sativum L.) apical senescence occurs only in long days (LD), and indeterminate growth is associated with elevated gibberellin (GA) levels in the shoot in short days (SD). Metabolism of GA(12) aldehyde was investigated by feeding shoots grown in SD or LD with [(14)C]GA(12) aldehyde through the cut end of the stem for 0.5 to 6 hours...

The rates of leaf and flower production were determined in peas ( Pisum sativum L.) of genotypes e sn hr (line 13), E Sn hr (line 60), and E Sn Hr (line G2), to assess the role of the interaction of alleles Sn and Hr with photoperiod in development. The rates at which flowers at successive nodes opened (AR) and leaves at successive nodes unfolded (...

In G2 peas senescence only takes place in long days. In order to determine the role of cytokinins in this process the endogenous cytokinins from vegetative shoots of G2 peas were characterized using gas chromatography-mass spectroscopy following purification by HPLC. Cytokinins were extracted and purified with and without the addition of 15N labell...

Polyamine content and arginine decarboxylase activity of apical buds were measured to determine whether polyamines are required to prevent apical senescence in pea. Polyamines were assayed as dansyl derivatives which were separated by reverse phase high performance liquid chromatography and detected by fluorescence spectrophotometry. High polyamine...

High performance liquid chromatography in combination with fluorescence spectrophotometry can be used to separate and quantitate polyamines (putrescine, cadaverine, spermidine, spermine), prepared as their dansyl derivatives, from plant tissue. The procedure gives sensitive and consistent results for polyamine determinations in plant tissue. In a s...

To determine the requirement for polyamines in gibberellin (GA) induced internode growth polyamine content was measured in internodes of peas of various internode phenotypes (slender, tall, dwarf, nana) with and without applied gibberellin (GA(3)) and polyamine synthesis inhibitors. Polyamines were assayed as dansyl derivatives which were separated...

The effect of various treatments on the apical senescence and polyamine content of apical buds of G2 peas was analysed. Defruiting prevented senescence and increased bud size and polyamine content. Exogenous applications of GA20 enhanced bud size and spermidine concentration. Applied spermidine had a slight effect on spermidine level but did not de...

Apical sencscence in G2 peas occurs only in long days in the presence of fruit. The effect of fruits could be caused by the export of a senescence hormone from the fruits to the shoot tip. Export of radiolabeled material from developing fruits of G2 peas grown in long days was therefore examined following injection of the pods with [14C]-sucrose, [...

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A19, A20, A29 and an A29 catabolit...

In the G2 line of peas (Pisum sativum L.), senescence of the shoot apex (which precedes leaf senescence) only occurs in long days (LD) though flowering is independent of photoperiod. It has been suggested that the photoperiodic control of senescence in G2 is mediated through different rates of seed growth. In LD seed growth is more rapid than in sh...

1. The uptake of indol-3-yl acetic acid ([1-14C]IAA, 0–2.0 M) into light-grown pea stem segments was measured under various conditions to investigate the extent to which mechanisms of auxin transport in crown gall suspension culture cells (Rubery and Sheldrake, Planta 118, 101–121, 1974) are also found in a tissue capable of polar auxin transport....