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A-C. Patterns of ray spacing in cross-sections of the xylem in S. monoica. All are in the same magnification ( x 13,6). A A rare case showing a pith ray (arrow). P, Pith. B A zone with high ray density. C A zone with a few rays. Note two huge rays. D Phloem anastomoses (arrows) between axial and radial phloem strands (s) at the edge of a huge ray. x 136
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The early-formed xylem of Suaeda monoica Forssk. ex J. F. Gmel (Chenopodiaceae) is temporarily rayless. Vascular rays differentiate during later stages of its xylem ontogeny. The rays in Suaeda are heterogeneous, and some of them are aggregated. The mature xylem of this species is characterized by two unique types of vascular rays: (1) rays with se...
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Citations
... ex J.F.Gmel. by Lev-Yadun and Aloni (1991). However, S. monoica is characterized by the presence of polycentric rays that are composed of several small rays and develop radially oriented vascular elements. ...
... ex J.F.Gmel. by Lev-Yadun and Aloni (1991). However, S. monoica is characterized by the presence of polycentric rays that are composed of several small rays and develop radially oriented vascular elements. ...
Barleria is known for its different growth forms such as herbs, shrubs, climbers, and rarely trees that show a wide range of variation in wood structure. We investigated the Indian species of Barleria and observed that all are characterized by the presence of included and intraxylary phloem. Included phloem is the strand of sieve elements embedded within the secondary xylem and is believed to perform the same general function as regular phloem (i.e. photosynthate transport). Internal/intraxylary phloem comprises sieve elements that are formed on the periphery of the pith. In the present investigation, a complete study of the stem anatomy of 36 taxa (29 species, one subspecies, two varieties, and four forms) of Indian Barleria species along with two outgroups (Crossandra infundibuliformis and Petalidium barlerioides) was carried out. This is the first comprehensive study on Indian Barleria and could be used for identification of species in the genus. Differences in the outline of stem and pith, the composition of the secondary xylem, variation in the number of the sieve elements within the included phloem islands, septation in fibres, fibre cell wall thickening, and ray types can be used for species delimitation. The present study revealed that depending on species, vessel elements were angular or oval, having a short tail at one end and a long tail on the other end, a short tail on both ends, a long tail on both ends, or without a tail. Among the species investigated, no consistency was observed in the secondary xylem rays. They were mostly uni- to biseriate in some species while in the remaining species they were uni- to multiseriate.
... They are radially elongated and sometimes even show the deposition of the xylem elements and appear like radially oriented vascular bundles. Lev-Yadun and Aloni [143] reported that these meristematic centres initiate in the large rays of the cambium due to repeated cell divisions in Suaeda monoica. However, the case of A. digitata differs from the S. monoica because the former species shows regular secondary growth and has a single ring of vascular cambium, whereas Suaeda monoica is characterized by the presence of successive cambia and other kinds of variant secondary growth [76,143]. ...
... Lev-Yadun and Aloni [143] reported that these meristematic centres initiate in the large rays of the cambium due to repeated cell divisions in Suaeda monoica. However, the case of A. digitata differs from the S. monoica because the former species shows regular secondary growth and has a single ring of vascular cambium, whereas Suaeda monoica is characterized by the presence of successive cambia and other kinds of variant secondary growth [76,143]. Similar types of rays have also been described in Hebanthe eriantha [120] and Argyreia splendense [51]. ...
Phloem is one of the vital tissues of the vascular system that plays a crucial role in the conduction of photosynthates. In vascular plants, it develops external to the vascular cambium but in a small fraction of eudicots (formerly known as dicots), it occurs within (interxylary) and inside (intraxylary) the secondary xylem. Ontogenetically, it is classified as Strychnos, Combretum, Azima, and Calycopteris types. In all four cases, phloem islands remain enclosed within the secondary xylem but each has unique origins. Similarly, the deposition of the phloem at the pith margin is common in several plants. It develops from procambial derivatives or adjacent pith cells or by initiating an intraxylary phloem cambium. Functionally, this cambium can produce only phloem or both secondary xylem and phloem. In some instances, the deposition of the secondary xylem and phloem in the same direction has also been documented. Some experimental evidence is available on the role of phloem but is it applicable to inter- and intraxylary phloem? The presence of inter- and intraxylary phloem is attributed to a defence mechanism against insects or plants that show sudden and enormous flowering or it can correlate with high temperatures or an unconducive climate in a desert region where sieve tube elements have become nonfunctional due to high temperatures. The present review is an attempt to analyse the role of interxylary and intraxylary phloem.
... The variations in size observed in the rays of S. parahyba var. amazonicum are mainly associated with anticlinal and transversal cellular division of the ray initials, as well as with the union, both vertical and lateral, of contiguous cambial rays (Lev-Yadun and Aloni 1991;Lev-Yadun and Aloni 1995). ...
Schizolobium parahyba var. amazonicum (paricá) is a promising forest species that has been planted in some states of the Amazon region in Brazil, to meet the demand of the plywood panel industry. The present work involves a study of the variations of the cambium and their impact on derivative tissues at different heights in the stem of S. parahyba var. amazonicum . Except for the tangential diameter of the fusiform initials (DFI) and the width of the xylem cell layer in differentiation (WXD), there was significant statistical variation between the evaluated axial positions for all anatomical parameters of the cambium. A strong positive correlation was noticed between the length of the fusiform initials (LFI) with ray height (RH) [r = 0.79, degree of freedom (DF) = 7, P < 0.05], vessel element length (VL) (r = 0.78, DF = 7, P < 0.05) and fiber length (FL) (r = 0.74, DF = 7, P < 0.05). The results of this study give quantitative support that the LFI is an important prognosis, not only for the VL and FL, but also for the rays, in hardwood species.
... Radial sieve tube elements have been reported in different genera and these have been grouped into at least three categories depending on the mechanism by which they are formed. The three categories are (1) naturally developed radial sieve elements in secondary phloem (Chavan et al. 1983;Rajput & Rao 1997;Rajput 2004;Angyalossy et al. 2012), (2) naturally developed radial sieve elements in secondary xylem (Den Outer & Veenendaal 1981;Lev-Yadun & Aloni 1991;Angyalossy et al. 2012;Gondaliya & Rajput 2016), and (3) artificially or traumatically induced radial sieve elements (Sharma et al. 1980;Aloni & Barnett 1996). Recently, we found radial sieve tubes in the rays of the secondary xylem in Aquilaria malaccensis, A. sinensis, A. crasna and Gyrinops versteeghii (Thymelaeaceae, Malvales). ...
New observations of radial sieve tubes in the secondary xylem of two genera and four species of agarwood — Aquilaria sinensis , A. crasna , A. malaccensis and Gyrinops versteeghii (Thymelaeaceae) — are presented in this study. The earliest radial sieve tubes in Gyrinops are formed in the secondary xylem adjacent to the pith. The radial sieve tubes originate from the vascular cambium and develop in both uniseriate and multiseriate ray tissue. In addition to sieve plates in lateral and end walls, scattered or clustered minute sieve pores are localized in the lateral wall of radial sieve tubes. There is a direct connection between radial sieve tubes in ray tissue and axial sieve tubes in interxylary phloem strands (IP), such as (i) connection by bending of radial sieve tube strands, (ii) connection of two IP strands by an oblique bridge, and (iii) connection of two IP strands at a right angle. The average number of radial sieve tubes and interxylary phloem was found to be 1.7 per mm ³ and 9.1 per mm ² in the secondary xylem. Considering the higher frequency of radial sieve tubes with the increasing thickness of the secondary xylem, the direct connections between radial and axial sieve tubes could play a significant role in assisting the translocation of metabolites in Aquilaria and Gyrinops .
... including the presence of successive cambia, diffuse porosity, simple perforation plates, intervessel pits alternate, scanty or vasicentric paratracheal parenchyma and nucleated fibers. The development of rays in Amaranthaceae s.l. has been controversial since they are not always recognized (Lev-Yadun and Aloni 1991;Rajput 2002;Carlquist 2003;Heklau et al. 2012;Rajput and Marcati 2013;Shelke et al. 2019). Some authors (Lev-Yadun and Aloni 1991;Heklau et al. 2012) mentioned that juvenile wood with successive cambia lacks rays, whereas at maturity, wood with successive cambia has rays, as is the case in the current subfamily Chenopodioideae. ...
... The development of rays in Amaranthaceae s.l. has been controversial since they are not always recognized (Lev-Yadun and Aloni 1991;Rajput 2002;Carlquist 2003;Heklau et al. 2012;Rajput and Marcati 2013;Shelke et al. 2019). Some authors (Lev-Yadun and Aloni 1991;Heklau et al. 2012) mentioned that juvenile wood with successive cambia lacks rays, whereas at maturity, wood with successive cambia has rays, as is the case in the current subfamily Chenopodioideae. ...
... does not have rays at the beginning of its development, which was not the case in some species of Iresine. However, Lev-Yadun and Aloni (1991) mentioned that during the transition from juvenile to mature wood, some hormones promote the development of rays through the anticlinal division of fusiform initial cells to originate radial initial cells once the plant has reached its maturity. Moreover, Shelke et al. (2019) mentioned that the absence of rays in herbaceous species of Amaranthaceae is related to reduced cambial activity and short fusiform initials. ...
Iresine is an American genus that belongs to Amaranthaceae s.l. To understand its stem anatomy and correlation with the habit and habitat, a comparative study was carried out. We present the most extensive stem anatomical survey of Iresine to date. Our observations agree with wood descriptions for other Amaranthaceae having simple perforation plates, intervessel pits alternate and nucleated fibers. Few species showed distinctive growth rings. Rays are heterocellular, multiseriate with meristematic centers. The occurrence of rays with meristematic centers is not related to habit or habitat, but suggests that water and photosynthates movement is complex through the axial–radial system. Species studied have successive cambia in concentric bands or patches. Seven species have distinctive characters as for I. latifolia (M.Martens & Galeotti) Hook.f. with two or three pairs pith bundles, I. rzedowskii Zumaya, Flores Olv. & Borsch with a thick periderm and I. cassiniiformis S.Schauer with lignified pith. Not all quantitative wood features follow the trends expected with habit but significant differences exist (P > 0.05) for some as fiber length. The tree species has the widest vessel diameter (81 µm) and the longest fiber length (570 µm), and shrubs show the highest variation. Canonical correlation analysis allowed to identifying that mean annual temperature, longitude and annual rainfall have an impact in the wood of Iresine species, especially in vessel and fiber wall thickness, intervessel pit diameter and fiber length. Iresine wood appears to be more susceptible to changes of mean annual temperature and precipitation showing its plasticity.
... Formation of successive cambia are not only unique to the family Amaranthaceae s.l., and successive cambia are present in most plant families of Caryophyllales (De Bary, 1884;Wilson, 1924;Metcalfe and Chalk, 1950;Balfour, 1965;Stevenson and Popham, 1973;Yarrow and Popham, 1981;De Mason, 1983;Simcha and Aloni, 1991;Rajput, 2002;Carlquist, 2003Carlquist, , 2007aMenezes et al., 2005;Heklau et al., 2012). However, Alternanthera philoxeroides, an aquatic species shows nonexistence of successive cambia . ...
... Therefore, to understand the behaviour of these cambial segments requires studies on the perennial plants. Simcha and Aloni (1991) studied stem anatomy of Suaeda monoica in relation to ray differentiation in fully grown individuals and their main aim was to investigate how rays develop in rayless taxa. Therefore, their study has not paid attention on the primary growth and how secondary growth initiates. ...
... In the present study also, both species showed absence of rays in the early part of the secondary growth but in thick stems, not only uni-triseriate rays were observed but also showed presence of several cells tall and wide rays. Incidence of such tall and wide multiseriate rays has also been reported in S. monoica by Simcha and Aloni (1991) and in other members of Amaranthaceae like Hebanthe eriantha (Rajput and Marcati, 2013). Occurrence of polycentric, multicellular rays has been reported in S. monoica by Simcha and Aloni (1991). ...
Amaranthaceae s.l. and its allied families like Amaranthaceae s.s., Chenopodiaceae s.s. and Phytolaccaceae s.s. are always debated in the literature about their pattern of secondary growth; when their stem diameter increases by forming successive cambia. In the present study, development of successive cambia and differentiation of its derivatives was investigated in Suaeda fruticosa and S. nudiflora (Amaranthaceae s.l.). After primary growth, the first complete ring of cambium was formed by the successive cambium due to failure in the development of interfascicular cambium between adjacent vascular bundles. The first ring of successive cambium initiated from the parenchymatous cells (pericyclic derivatives)external to the protophloem. This newly formed cambium was functionally bidirectional and produced secondary xylem centripetally and phloem centrifugally. Subsequent renewal of cambium was observed as small segments instead of complete ring. They interconnect with existing cambium and form anastomosing network. Due to the renewal of small sectors, the secondary phloem formed by earlier cambial segments became enclosed within the secondary xylem and conjunctive tissue. Formation of vessels and sieve elements were found confined only to few fusiform cells while rest of the cambial sector exclusively produced conjunctive tissue on either side. The secondary xylem formed in the beginning of successive rings of xylem remained rayless while thick stems showed presence of heterocellular rays with several cells in height and width. Accumulation of starch along with the presence of nuclei in the xylem fibres even after deposition of the secondary wall is consistent feature in both the species.
... ray cambium as reported by Patil et al. 2011) is a rare feature and is reported in Thladiantha dubia Bunge (Metcalfe & Chalk 1950) and in some other members of Cucurbitaceae (Carlquist 1992b). Lev-Yadun & Aloni (1991) reported formation of vascular elements in the tall and large heterocellular rays, referred to as 'polycentric rays'. In the present study, rays forming vascular elements are not polycentric. ...
... In the present study, rays forming vascular elements are not polycentric. In polycentric rays there are several meristematic centres distributed throughout the large rays (Lev-Yadun & Aloni 1991). However, in the present study only marginal cells become meristematic and differentiate into xylem and phloem derivatives. ...
Background – Population growth of lianas in the tropical forest is credited to their ability of CO 2 sequestration and efficiency of the narrow stems to supply water required for the amount of foliage it bears. Turbina corymbosa (L.) Raf. (Convolvulaceae Juss.) is one of the fast-growing invasive species of scrambling woody lianas. It covers trees entirely within a short period to compete with above-ground resources (particularly sunlight). However, no information is available on how it manages to cope up with an increasing demand of water supply and mineral nutrients. What are the structural and developmental patterns adapted by this species to expand the stem diameter for efficient supply of below-ground resources? Therefore, our aim was to investigate the secondary growth patterns and structure of secondary xylem and phloem in T. corymbosa. Methods – Several samples of the stem with various diameters were studied using a histological method. Morphological and anatomical analyses were carried out using light microscopy. Key results – With the initiation of secondary growth, stems lose their circular outline rapidly due to unequal deposition of secondary xylem and formation of successive cambia. New successive cambia initiate from parenchymatous cells as small crescent-shaped fragments on asymmetric/opposite sides and result in a different stem conformation. Though several segments of successive cambia are formed, very few stem samples form complete cambium rings. The secondary xylem formed by successive cambia is diffuse porous with indistinct growth rings and is composed of both wide and narrow (fibriform) vessels, tracheids, fibres, axial and ray parenchyma cells. The secondary phloem consists of sieve tube elements, companion cells, axial and ray parenchyma cells. In fully grown plants, cambial action (internal cambium) occurrs between the intraxylary phloem and protoxylem and produces secondary xylem and phloem near the pith region. Conclusion – Structural alterations and unequal deposition of conducting elements, occurrence of intraxylary phloem and flattening of the stem are suggested to facilitate rapid growth of the plants by providing required minerals and nutrients. Internal cambium formed at the periphery of the pith is bidirectional and produces secondary xylem externally and intraxylary phloem internally. Continued development of intraxylary phloem from the internal cambium provides an additional path for rapid and safe translocation of photosynthates. © 2018 Meise Botanic Garden and Royal Botanical Society of Belgium. All rights reserved.
... Pedersen (Amaranthaceae ;Rajput & Marcati, 2013) and Suaeda monoica Forssk. ex J.F.Gmel (Chenopodiaceae; Lev-Yadun & Aloni, 1991). Other Iresine species should be examined to ascertain whether multiseriate rays with a meristematic center are characteristic of the genus or unique to I. latifolia, or whether they are associated with the shrub or scandent habit. ...
The size of the axial cell elements of wood, vessel elements and fibers, increases or decreases from pith to stem periphery in the species that have been studied with successive cambium such as members of the Menispermaceae. Iresine latifolia (Amaranthaceae) was selected for this study because it is a scandent shrub widely distributed in Mexico with successive cambia. The objectives were to quantify vessel element and fiber lengths in each of the vascular rings, to evaluate whether cellular size increases or decreases from pith to periphery, and to describe its wood. Macerations were performed for each of the secondary xylem rings present in 3 individual samples, and permanent slides were prepared using conventional procedures for wood. Observations showed that I. latifolia has 13–36 concentric rings, each ring showing an active cambium. Like other species of Amaranthaceae, there are nucleated fibers and multiseriate rays with a meristematic center. Variance analyses showed significant differences between vessel element and fiber lengths between only some of the vascular rings from pith to periphery. These results suggest that the parenchyma cells, from which the new cambium is derived, reach the size of the fusiform initial cells early in the differentiation process.
... These true rays intergrade with rayless condition, where rays may be replaced by radial strips of axial parenchyma (Heklau et al. 2012). Occurrence of temporary raylessness has already been reported by previous researchers (Barghoorn 1941;Lev-Yadun and Aloni 1991;Rajput 2001;Rajput and Rao 2000;Rajput et al. 2010). Similar feature has also documented in our earlier studies on the Amaranthaceae (Rajput 2001(Rajput , 2002. ...
... In addition to the present study, the phenomenon of development of rays in the mature parts of the temporary rayless wood is also observed in other species (Barghoorn 1941;Lev-Yadun and Aloni 1991;Rajput 2001Rajput , 2002. According to Lev-Yadun and Aloni (1991) ray initiation, followed by its development and increase in ray size is a common phenomenon with maturation of wood in plants. ...
Hebanthe eriantha (Poir.) Pedersen, a climbing species of the Amaranthaceae increases in stem thickness by forming successive cambia. The family is dominated by herbaceous species and is constantly under discussion due to its disputed nature of the meristem. In the young stem small alternate segments of vascular cambium cease to divide and new arc of cambium initiates outside to it. The newly formed arcs connect with pre-existing alternate segments of cambium to complete the ring. On the contrary, in thick stems, instead of small segments, complete ring of cambium is replaced by new one. These new alternate segments/cambia originate from the parenchyma cells located outside to the phloem produced by previous cambium. Cambium is storied and exclusively composed of fusiform initials while ray cells remain absent at least in the early part of the secondary growth. However, large heterocellular rays are observed in 15-mm diameter stems but their frequency is much lower. In some of the rays, ray cells become meristematic and differentiate into radially arranged xylem and phloem elements. In fully grown plants, stems are composed of several successive rings of secondary xylem alternating with secondary phloem. Secondary xylem is diffuse-porous and composed of vessels, fibres, axial parenchyma while exceptionally large rays are observed only in the outermost regions of thick stems. Vessel diameter increases progressively from the centre towards the periphery of stems. Although the origin of successive cambia and composition of secondary xylem of H. eriantha remains similar to other herbaceous members of Amaranthaceae, the occurrence of relatively wider and thick-walled vessels and large rays in fully grown plants is characteristic to climbing habit.
