Showing papers on "Vascular cambium published in 2013"

Hormonal signals involved in the regulation of cambial activity, xylogenesis and vessel patterning in trees

Abstract: The radial growth of plant stem is based on the development of cribro-vascular cambium tissues. It affects the transport efficiency of water, mineral nutrients and photoassimilates and, ultimately, also plant height. The rate of cambial cell divisions for the assembly of new xylem and phloem tissue primordia and the rate of differentiation of the primordia into mature tissues determine the amount of biomass produced and, in the case of woody species, the wood quality. These complex physiological processes proceed at a rate which depends on several factors, acting at various levels: growth regulators, resource availability and environmental factors. Several hormonal signals and, more recently, further regulatory molecules, have been shown to be involved in the induction and maintenance of cambium and the formation of secondary vascular tissues. The control of xylem cell patterning is of particular interest, because it determines the diameter of xylem vessels, which is central to the efficiency of water and nutrient transport from roots to leaves through the stem and may strongly influence the growth in height of the tree. Increasing scientific evidence have proved the role of other hormones in cambial cell activities and the study of the hormonal signals and their crosstalking in cambial cells may foster our understanding of the dynamics of xylogenesis and of the mechanism of vessel size control along the stem. In this article, the role of the hormonal signals involved in the control of cambium and xylem development in trees and their crosstalking are reviewed.

Cell-to-Cell Movement of Two Interacting AT-Hook Factors in Arabidopsis Root Vascular Tissue Patterning

Abstract: The xylem and phloem, major conducting and supporting tissues in vascular plants, are established by cell division and cell-type specification in the procambium/cambium. The organization of the xylem, phloem, and procambium/cambium is tightly controlled. However, the underlying regulatory mechanisms remain largely unknown. In this study, we report the discovery of two transcription factors, AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN 3 (AHL3) and AHL4, which regulate vascular tissue boundaries in Arabidopsis thaliana roots. In either of the knockout mutants of AHL3 and AHL4, encoding closely related AT-hook transcription factors, a misspecification of tissue boundaries between the xylem and procambium occurred and ectopic xylem developed in the procambium domain. In plants, specific types of transcription factors can serve as direct intercellular signals by moving from one cell to another, playing crucial roles in tissue patterning. Adding to this paradigm, AHL4 moves actively from the procambium to xylem in the root meristem to regulate the tissue boundaries. When the intercellular movement of AHL4 was impaired, AHL4 could not complement the xylem phenotype in the ahl4. Furthermore, AHL4 revealed unique characteristics in that it interacts with AHL3 in vivo and that this interaction facilitates their intercellular trafficking. Taken together, this study uncovered a novel mechanism in vascular tissue patterning that requires the intercellular trafficking of two interacting transcription factors.

Genetic and hormonal regulation of cambial development

Abstract: The stems and roots of most dicot plants increase in diameter by radial growth, due to the activity of secondary meristems. Two types of meristems function in secondary plant body formation: the vascular cambium, which gives rise to secondary xylem and phloem, and the cork cambium, which produces a bark layer that replaces the epidermis and protects the plant stem from mechanical damage and pathogens. Cambial development, the initiation and activity of the vascular cambium, leads to an accumulation of wood, the secondary xylem tissue. The thick, cellulose-rich cell walls of wood provide a source of cellulose and have the potential to be used as a raw material for sustainable and renewable energy production. In this review, we will discuss what is known about the mechanisms regulating the cambium and secondary tissue development.

The regulation of cambial activity in Chinese fir (Cunninghamia lanceolata) involves extensive transcriptome remodeling

Abstract: Chinese fir (Cunninghamia lanceolata), a commercially important tree for the timber and pulp industry, is widely distributed in southern China and northern Vietnam, but its large and complex genome has hindered the development of genomic resources. Few efforts have focused on analysis of the modulation of transcriptional networks in vascular cambium during the transition from active growth to dormancy in conifers. Here, we used Illumina sequencing to analyze the global transcriptome alterations at the different stages of vascular cambium development in Chinese fir. By analyzing dynamic changes in the transcriptome of vascular cambium based on our RNA sequencing (RNA-Seq) data at the dormant, reactivating and active stages, many potentially interesting genes were identified that encoded putative regulators of cambial activity, cell division, cell expansion and cell wall biosynthesis and modification. In particular, the genes involved in transcriptional regulation and hormone signaling were highlighted to reveal their biological importance in the cambium development and wood formation. Our results reveal the dynamics of transcriptional networks and identify potential key components in the regulation of vascular cambium development in Chinese fir, which will contribute to the in-depth study of cambial differentiation and wood-forming candidate genes in conifers.

Symplesiomorphies in the WUSCHEL clade suggest that the last common ancestor of seed plants contained at least four independent stem cell niches

Abstract: Evolutionary studies addressing plant architecture have uncovered several significant dichotomies between lower and higher land plant radiations, which are based on differences in meristem histology and function. Here, we assess the establishment of different stem cell niches during land plant evolution based on genes of the stem cell-promoting WUSCHEL (WUS) clade of the WOX (WUSCHEL-related homeobox) gene family. WOX gene orthology was addressed by phylogenetic analyses of full-length WOX protein sequences and cellular expression pattern studies indicate process homology. Gene amplifications in the WUS clade were present in the last common ancestor (LCA) of extant gymnosperms and angiosperms. Whereas the evolution of complex multicellular shoot and root meristems relates to members in the WUS/WOX5 sub-branch, the evolution of marginal and plate meristems or the vascular cambium is associated with gene duplications that gave rise to WOX3 and WOX4, respectively. A fourth WUS clade member, WOX2, was apparently recruited for apical cell fate specification during early embryogenesis. The evolution and functional interplay of WOX3 and WOX4 possibly promoted a novel mode of leaf development, and evolutionary adaptations in their activities have contributed to the great diversity in shape and architecture of leaves in seed plants.

An early origin of secondary growth: Franhueberia gerriennei gen. et sp. nov. from the Lower Devonian of Gaspé (Quebec, Canada)

Abstract: Premise of the study Secondary xylem (wood) produced by a vascular cambium supports increased plant size and underpins the most successful model of arborescence among tracheophytes. Woody plants established the extensive forest ecosystems that dramatically changed the Earth's biosphere. Secondary growth evolved in several lineages in the Devonian, but only two occurrences have been reported previously from the Early Devonian. The evolutionary history and phylogeny of wood production are poorly understood, and Early Devonian plants are key to illuminating them. Methods A fossil plant preserved anatomically by cellular permineralization in the Lower Devonian (Emsian, ca. 400-395 million years old) Battery Point Formation of Gaspe Bay (Quebec, Canada) is described using the cellulose acetate peel technique. Key results The plant, Franhueberia gerriennei Hoffman et Tomescu gen. et sp. nov., is a basal euphyllophyte with a centrarch protostele and metaxylem tracheids with circular and oval to scalariform bordered multiaperturate pits (P-type tracheids). The outer layers of xylem, consisting of larger-diameter P-type tracheids, exhibit the features diagnostic of secondary xylem: radial files of tracheids, multiplicative divisions, and a combination of axial and radial components. Conclusions Franhueberia is one of the three oldest euphyllophytes exhibiting secondary growth documented in the Early Devonian. Within the euphyllophyte clade, these plants represent basal lineages that predate the evolution of stem-leaf-root organography and indicate that underlying mechanisms for secondary growth became part of the euphyllophyte developmental toolkit very early in the clade's evolution.

Xylem Development in Trees: From Cambial Divisions to Mature Wood Cells

Abstract: As one of the major parts of the biosphere, trees will play a significant role in the near future because of an increasing demand for wood as the most important natural raw material. Wood is generated by the vascular cambium and enables water transportation as well as providing mechanical support to the tree. Furthermore, it is the main renewable source for paper, buildings, furniture, boards and fuel. In recent decades intriguing developments in cell, molecular and structural biology have led to an integrated view of wood formation, from its start in the cambium by cell division, via cell expansion and cell wall thickening, to programmed cell death. These complex processes involve the interaction of both exogenous factors, such as photoperiod and temperature, and endogenous regulators, such as phytohormones. In addition, the coordinated expression of the numerous genes implicated in the biosynthesis of the major wood components—cellulose, hemicelluloses and lignin—drives the ordered development of wood. The huge amount of literature in the different fields of wood formation cannot be reviewed here in detail; rather, the aim of this chapter is to give a brief overview of the essential steps leading to mature wood cells, with an emphasis on current progress obtained by modern techniques which have increased our understanding of wood formation.

Interxylary phloem: Diversity and functions

Abstract: Interxylary phloem is here defined as strands or bands of phloem embedded within the secondary xylem of a stem or root of a plant that has a single vascular cambium. In this definition, interxylary phloem differs from intraxylary phloem, bicollateral bundles, pith bundles, and successive cambia. The inclusive but variously applied terms included phloem and internal phloem must be rejected. Histological aspects of interxylary phloem are reviewed and original data are presented. Topics covered include duration of interxylary phloem; relationship in abundance between sieve tubes in external phloem and interxylary phloem; distinctions between interxylary and intraxylary phloem; presence of parenchyma, fibers, and crystals in the interxylary phloem strands; development of cambia within interxylary phloem strands; three-dimensionalization and longevity of phloem, systematic distribution of interxylary phloem; physiological significance; and habital correlations. No single physiological phenomenon seems to explain all instances of interxylary phloem occurrence, but rapidity and volume of photosynthate transport seem implicated in most instances.

Auxin-responsive DR5 promoter coupled with transport assays suggest separate but linked routes of auxin transport during woody stem development in Populus.

Abstract: Polar auxin transport (PAT) is a major determinant of plant morphology and internal anatomy with important roles in vascular patterning, tropic growth responses, apical dominance and phyllotactic arrangement Woody plants present a highly complex system of vascular development in which isolated bundles of xylem and phloem gradually unite to form concentric rings of conductive tissue We generated several transgenic lines of hybrid poplar (Populus tremula x alba) with the auxin-responsive DR5 promoter driving GUS expression in order to visualize an auxin response during the establishment of secondary growth Distinct GUS expression in the cambial zone and developing xylem-side derivatives supports the current view of this tissue as a major stream of basipetal PAT However, we also found novel sites of GUS expression in the primary xylem parenchyma lining the outer perimeter of the pith Strands of primary xylem parenchyma depart the stem as a leaf trace, and showed GUS expression as long as the leaves to which they were connected remained attached (ie, until just prior to leaf abscission) Tissue composed of primary xylem parenchyma strands contained measurable levels of free indole-3-acetic acid (IAA) and showed basipetal transport of radiolabeled auxin (3H-IAA) that was both significantly faster than diffusion and highly sensitive to the PAT inhibitor NPA Radiolabeled auxin was also able to move between the primary xylem parenchyma in the interior of the stem and the basipetal stream in the cambial zone, an exchange that was likely mediated by ray parenchyma cells Our results suggest that (a) channeling of leaf-derived IAA first delineates isolated strands of pre-procambial tissue but then later shifts to include basipetal transport through the rapidly expanding xylem elements, and (b) the transition from primary to secondary vascular development is gradual, with an auxin response preceding the appearance of a unified and radially-organized vascular cambium

CLE Peptides in Vascular Development

Abstract: The plant vascular system consists of two conductive tissues, phloem and xylem. The vascular meristem, namely the (pro-)cambium, is a stem-cell tissue that gives rise to both xylem and phloem. Recent studies have revealed that CLAVATA3/Embryo Surrounding Region-related (CLE) peptides function in establishing the vascular system through interaction with phytohormones. In particular, TDIF/CLE41/CLE44, phloem-derived CLE peptides, promote the proliferation of vascular cambium cells and prevent them from differentiating into xylem by regulating WOX4 expression through the TDR/PXY receptor. In this review article, we outline recent advances on how CLE peptides function in vascular development in concert with phytohormones through mediating cell-cell communication. The perspective of CLE peptide signaling in vascular development is also discussed.

A Callixylon (Archaeopteridales, Progymnospermopsida) trunk with preserved secondary phloem from the Late Devonian of Morocco.

Abstract: PREMISE OF THE STUDY During the Devonian, the evolution of secondary phloem produced by a bifacial vascular cambium was a key innovation that increased the ability of plants within the lignophyte clade to redistribute photosynthates and other organic compounds throughout their body. Unraveling the secondary phloem anatomy of the first arborescent lignophytes is crucial to understand the evolution of this tissue and the physiology of early trees. METHODS A 10 cm wide stem of Callixylon with preserved secondary phloem from the Famennian of Morocco is described using thin-sections. KEY RESULTS The secondary phloem of this Callixylon zalesskyi-type of stem is composed of fibers, sclereids, rays, axial parenchyma, and putative sieve cells. Fibers differentiate early and are relatively abundant in the inner phloem. In the older phloem, fibers are arranged in tangential bands alternating with extensive layers of axial parenchyma. Changes between the young and old phloem involve the periclinal division and radial elongation of the axial parenchyma cells. The presence of fibers in the inner, presumably functional phloem, combined with evidence for rhythmicity in the production of different phloem cell types are documented for the first time in detail in an archaeopteridalean progymnosperm. No periderm was observed within the preserved seven millimeters of bark tissues. CONCLUSIONS The secondary phloem anatomy supports a close affinity of archaeopteridalean progymnosperms with both aneurophytalean progymnosperms and seed plants. The production of secondary phloem might have provided an advantage to these first arborescent lignophytes over other types of Devonian early trees, especially in dry conditions.

Stem anatomy and development of successive cambia in Hebanthe eriantha (Poir.) Pedersen: a neotropical climbing species of the Amaranthaceae

Abstract: 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.

Transcriptional Analysis Provides New Insights into Cold- and Dehydration-Tolerance Signaling Pathways and on Regulation of Stem Cell Activity in the Vascular Cambium of Poplar

Abstract: Stem cells play a critical role in the regulation of plant growth and development. Vascular cambium is the lateral meristem, producing secondary vascular elements in trees. Poplar cambium arrests growth at the onset of winter in northern climates to prevent freezing-related damage. We used cryosectioning and laser microdissection to isolate dormant and active cambium cells from stems of the poplar clone Nanlin 95 for transcriptome-wide analysis using the Affymetrix Poplar Genome Array. We observed that genes predicted to participate in systemic interaction with the environment performed well in dormant cambium and genes about cell cycle and DNA processing did well in active cambium. The dormant cambium was characterized by the upregulation of pathways controlling the expression of several cold- and dehydration-induced transcripts, resemble stress response signaling pathways characterized in Arabidopsis thaliana. The expression of PeWOX4, PeCLE41/44, and PeTDR/PXY suggests the existence of a system that maintains the cambium by enhancing proliferation, whereas the detection of transcripts of CLV3-like genes indicates the existence of a pathway that involves PeCLE12, PeCLE13 or PeCLE25, and PeWOX4 to promote the differentiation of stem cells in the poplar vascular cambium, much like the system of WUS (WUSCHEL)–CLV (CLAVATA) which promote differentiation in the shoot apical meristem of Arabidopsis.

Secondary growth and occurrence of laticifers in the root of papaya (Carica papaya L.)

Abstract: The pattern of secondary growth and occurrence of laticifers was studied in the tap root of papaya (Carica papaya L., Caricaceae). The vascular cambium was differentiated, producing secondary phloem centrifugally and xylem centripetally. Phloem was composed of sieve tube members, companion cells, fibres and parenchyma, whereas the xylem was mainly thin-walled parenchyma tissue with lignified vessels embedded in it. The root vascular tissue was characterized by the occurrence of isolated, narrow, but thick-walled articulated laticiferous cells. Fusiform cambial cells produced laticiferous cells only in the centripetal direction, whereas ray cambial cells produced these cells both centripetally and centrifugally. Laticifers underwent intrusive tip growth and their maturation was marked by the disappearance of transverse septa. These cells appeared as narrow segmented cells close to the cambial zone whereas in the xylem they were isolated and elongated with sinuous or constricted walls. Radial growth...

Study on Rooting Culture and Rooting Anatomy of Tree Peony ‘Wulong Pengsheng’ Regenerated Shoots

Abstract: The tissue-cultured seedlings of tree peony‘Wulong Pengsheng’were used to study the effects of different plant growth regulators,culture methods,and holdfast on rooting.The morphological structure change during rooting was also observed using the method of paraffin section.The result showed that the best combination of plant growth regulators for rooting was IBA 3.0 mg.L-1 + NAA 0.6 mg.L-1.The treatment under the temperature of 4℃ for ten days was benefit to rooting,and the rate could reach 75.67%.It was identified that the adventitious root primordia of shoot in vitro originated from the vascular cambium cells,especially,the cross areas of cambium and pith ray and they started to differentiate at the 5th day and lasted to the 12th day.If the shoots were cultured in the root inducing medium for 12 days,it would lead to not only descend of rooting rate,but also showing callus of stem base,and leaf senescent.However,if they were transferred into the medium without hormone in time,the root primordial protruded the epidermis and developed normally after 5 days’culture.

Progymnospermopsida) trunk with preserved secondary phloem from the late devonian of morocco 1

Abstract:  Premise of the study: During the Devonian, the evolution of secondary phloem produced by a bifacial vascular cambium was a key innovation that increased the ability of plants within the lignophyte clade to redistribute photosynthates and other organic compounds throughout their body. Unraveling the secondary phloem anatomy of the fi rst arborescent lignophytes is crucial to understand the evolution of this tissue and the physiology of early trees.  Methods: A 10 cm wide stem of Callixylon with preserved secondary phloem from the Famennian of Morocco is described using thin-sections.  Key results: The secondary phloem of this Callixylon zalesskyi -type of stem is composed of fisclereids, rays, axial parenchyma, and putative sieve cells. Fibers differentiate early and are relatively abundant in the inner phloem. In the older phloem, fi bers are arranged in tangential bands alternating with extensive layers of axial parenchyma. Changes between the young and old phloem involve the periclinal division and radial elongation of the axial parenchyma cells. The presence of fiin the inner, presumably functional phloem, combined with evidence for rhythmicity in the production of different phloem cell types are documented for the fi rst time in detail in an archaeopteridalean progymnosperm. No periderm was observed within the preserved seven millimeters of bark tissues.  Conclusions: The secondary phloem anatomy supports a close affi nity of archaeopteridalean progymnosperms with both aneurophytalean progymnosperms and seed plants. The production of secondary phloem might have provided an advantage to these fi rst arborescent lignophytes over other types of Devonian early trees, especially in dry conditions.

Morphology and structure of mycorrhiza and distribution of endophytic fungus in Vaccinium uliginosum L.in Changbai Mountain

Abstract: Morphology and structure of the mycorrhiza and the distribution of the endophytic fungus in Vaccinium uliginosum L.in Changbai Mountain were observed and studied.The results showed that periderm was composed of 3-6-layer phellem cells in secondary root structure of the Vaccinium uliginosum L.,while vascular cambium and secondary phloem with 1-2-layer cells were not clear.The hair root was covered with mycelium layer loosely or tightly without root hair;endophytic fungus infected periderm and xylem without changing basic anatomic structure of the root.A preliminary observation indicated that the root of the Vaccinium uliginosum L.distributed in three types,ERM,DSE and VAM.Epidermal cell wall with the mycelium was obviously thickened.Furthermore,endophytic fungi were parasitic on the roots of all the Vaccinium uliginosum L..

PtrHB7, a class III HD-Zip Gene, Plays a Critical Role in Regulation of Vascular Cambium Differentiation in Populus

Abstract: 在树的第二等的生长的一个关键问题是脉管的形成层房间的区别怎么被指导到 concurrentlyform 二不同纸巾：木部或韧皮部。类 III homeodomain 白氨酸拉链(HD 压缩 III ) 基因被知道在主要、第二等的 growth.However 的进程在脉管的系统的开始， patterning，和区别玩 criticalroles，这些基因怎么控制第二等的脉管的区别的机制是未知的。这里，我们显示出那 Populus 类 III HD 压缩基因， PtrHB7，优先地在 cambial 被表示地区。压制 PtrHB7 的植物在木部与减小在脉管的纸巾显示了重要变化但是韧皮部的增加。Transcriptionalanalysis 表明调整木部区别的基因是下面调整的，而基因调整韧皮部 differentiationwere 起来调整。相应地， PtrHB7 overexpression 向木部房间提高了 cambial 房间的区别，但是禁止了韧皮部区别。cambial 房间区别上的 PtrHB7 规定与它的抄本丰富被联系。一起，结果 demonstratedthat PtrHB7 在在剂量依赖者 manner.Key 在 processof Populus 第二等的生长控制在第二等的木部和韧皮部纸巾之间的平衡区别起一个关键作用词：