机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的局部效应及其与茉莉酸分布的关系

采用同位素示踪技术和实验形态学的方法揭示茉莉酸在木本植物巴西橡胶树(Hevea brasiliensis Mull．Arg．)中的分布和运输的特点,并分析其与机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的诱导效应之间的关系。外施的茉莉酸进入体内后,在较长时间内大部分集中在施用部位。机械伤害阻止外施的茉莉酸进入体内,同时,又使进入的茉莉酸阻滞在受伤部位的附近。与茉莉酸在草本植物中可以向上和向下运输的情况不同,茉莉酸在木本植物巴西橡胶树中主要是向下运输的。机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的诱导效应是局部的,只在受伤和施用茉莉酸部位的树皮中诱导次生乳管的形成。机械伤害削弱外源茉莉酸对次生乳管分化的诱导效应,这与机械伤害阻止外源茉莉酸进入有关。研究结果表明,体内高水平的茉莉酸是诱导巴西橡胶树次生乳管分化所必需的。     

机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的局部效应及其与茉莉酸分布的关系

采用同位素示踪技术和实验形态学的方法揭示茉莉酸在木本植物巴西橡胶树(Hevea brasiliensis Mull.Arg.)中的分布和运输的特点,并分析其与机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的诱导效应之间的关系.外施的茉莉酸进入体内后,在较长时间内大部分集中在施用部位.机械伤害阻止外施的茉莉酸进入体内,同时,又使进入的茉莉酸阻滞在受伤部位的附近.与茉莉酸在草本植物中可以向上和向下运输的情况不同,茉莉酸在木本植物巴西橡胶树中主要是向下运输的.机械伤害和外施茉莉酸对巴西橡胶树次生乳管分化的诱导效应是局部的,只在受伤和施用茉莉酸部位的树皮中诱导次生乳管的形成.机械伤害削弱外源茉莉酸对次生乳管分化的诱导效应,这与机械伤害阻止外源茉莉酸进入有关.研究结果表明,体内高水平的茉莉酸是诱导巴西橡胶树次生乳管分化所必需的.     

Structure of the Bark and Clonal Variability in Hevea brasiliensis Muell. Arg. (Willd. ex A. Juss.)

Detailed studies have been made on the structure of the barkof ten Hevea clones and the clonal variabilities with regardto the density and size of ray groups, density of laticifersper row per unit circumference of the tree, diameter of laticifersand the extent of connection between laticifers. Clonal variabilitywas highly significant with regard to the density of ray groups,ray height, ray width in the laticifer layer and the laticifercharacters. The influence of ray characters on the orientationof laticifers and thereby its quantity is discussed. The scopeof using anatomical parameters for clone identification is examined. Hevea brasiliensis, Para rubber tree, laticifers, bark (structure), anatomy, clonal variability, rubber     

Occurrence of Intraxylary Phloem in Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.

The occurrence of intraxylary phloem in Hevea brasiliensis isreported. The phloem elements were observed as strands associatedwith the protoxylem group in the pericentral region. The natureand importance of such tissue in this species are discussed. Hevea brasiliensis, intraxylary phloem, laticifers, tapping     

Histochemical study of detailed laticifer structure and rubber biosynthesis-related protein localization in <Emphasis Type="Italic">Hevea brasiliensis</Emphasis> using spectral confocal laser scanning microscopy

In Hevea brasiliensis, laticifers produce and accumulate rubber particles. Despite observation using histochemical methods, development stage structure and structures with ceasing functions have rarely been described. Spectral confocal laser scanning microscopy with Nile red staining simplifies laticifer structure observation in tangential sections while enhancing the resolution. Laticifer and ray images were extracted from unmixed images and used to monitor changes during growth. A laticifer network structure developed from increased anastomoses between adjoining laticifers outside of the conducting phloem, but because of increased radial division and growth of rays, the network structure ruptured and disintegrated. We also investigated immunohistochemical localization of two rubber particle-associated proteins in the laticifers: small rubber particle protein (SRPP) and rubber elongation factor (REF). Mature bark test results show that SRPP is localized only in the laticifer layers in the conducting phloem; REF is localized in all laticifer layers. Because SRPP plays a positive role in rubber biosynthesis, results show that the rubber biosynthesis capability of laticifers is concentrated where rays and the sieve tube actively transport metabolites.     

The distribution of plasmodesmata in the phloem ofHevea brasiliensis in relation to laticifer loading

Summary Cell to cell connections, including plasmodesmata and perforations, were examined in the non-conducting secondary phloem ofHevea brasiliensis. Samples were taken from trunks of numerous trees, from several clones, and prepared for thin sectioning and transmission or scanning electron microscopy and as optical sections for fluorescence microscopy. Numerous plasmodesmata were found clustered in primary pit-fields between the ray and axial parenchyma cells. Between the laticifers and adjacent parenchyma sheath cells, structures corresponding to functional plasmodesmata were not observed. But some unusual structural features were occasionally seen in these walls. These observations are discussed in relation to the possible function of the cell types, and to the loss of latex on the tapping ofHevea. It is suggested that the loading of the laticifer might first require a symplastic pathway for the transport of metabolites, at the end of which the assimilates must enter the apoplast. A transmembrane active transport system then transfers the metabolites in the laticifer. The presumable role of parenchyma cells in the loading of laticifers is emphasized.     

Ultrastructure of Non-Articulated Laticifers in Allamanda violacea

Ultrastructure studies on the differentiation of non-articulatedbranched laticifers in Allamanda violacea Gardn. were carriedout. Growing laticifers show sequential changes. In the earlystage, the laticifers possess electron dense cytoplasm, abundantmitochondria, ER, ribosomes, small vacuoles, nucleus and plastidwith starch-grains. The ER dilates to form small vacuoles whichcoalesce at the later stages. A large central vacuole is formedin the mature laticifers due to the cellular autophagy of cytoplasmincluding the cell organelles. At this stage, the mitochondriapossess a few cristae and plastids with plastoglobuli and smallstarch grains. Towards the end of differentiation the cytoplasmis restricted to a thin parietal layer along the cell wall,the remaining organelles being either reduced in number or degenerate.Plasmodesmata and primary pit fields are occasionally observedbetween the laticifer and the adjacent parenchyma cell. Allamanda violacea, laticifers, ultrastructure     

巴西橡胶树HbSUT3和HbSUT5 mRNA在嫩茎和中脉中的原位杂交分析

为研究巴西橡胶树(Hevea brasiliensis)中HbSUT3和HbSUT5基因的功能,采用地高辛标记的RNA探针与橡胶树嫩茎和中脉两种组织切片分别进行RNA原位杂交,对这2种SUT基因在组织中的表达区域与表达特点进行了分析。结果表明,在橡胶树嫩茎中,两个SUT基因主要在树皮的韧皮部和皮层细胞中表达;在中脉中,两个SUT基因在除木质部导管系统外的其它部位均有表达;HbSUT3基因在嫩茎和中脉中的表达量相近,而HbSUT5基因在嫩茎中的表达量远高于中脉。这些揭示HbSUT3和HbSUT5基因可能广泛参与韧皮部装载、蔗糖运输与库细胞供给等活动,同时两个SUT基因也存在功能分化。     

Age-dependent and jasmonic acid-induced laticifer-cell differentiation in anther callus cultures of rubber tree

Main conclusion

Callus cultures of rubber tree may serve as an efficient model to screen and study environmental factors and phytohormones that stimulate laticifer cell differentiation and improve latex yield. The number of laticifer cells in bark is one of the most important factors determining the biosynthesis and economic value of rubber trees (Hevea brasiliensis). The differentiation of laticifer cells in planta has been characterized, whereas laticifer-cell differentiation in callus cultures in vitro is largely unknown. In this study, we present molecular and physiological evidences for laticifer-cell differentiation in calli derived from rubber tree anthers. RT-PCR analysis showed that three key genes rubber elongation factor (REF), small rubber particle protein (SRPP), and cis-prenyl transferase (CPT) that are essential in latex biosynthesis in rubber tree bark also were transcribed in anther calli. Laticifer cell development in callus cultures was age-dependent; the cells began to appear at 58 days after initiation of culture, and the percentage of laticifer cells increased steadily with increasing callus age. Addition of 0–2 mg/L jasmonic acid (JA) to the media significantly promoted the differentiation of laticifer cells in callus cultures. However, JA concentrations higher than 3 mg/L were not optimum for laticifer cells differentiation; this result was not observed in previous in planta studies. Laticifer cells differentiated on media with pH 5.8–7.0, with an optimum of pH 6.2, whereas a higher pH inhibited differentiation. These results indicate that the anther-derived rubber tree callus may serve as a new and more efficient model to study environmental factors that influence laticifer cell differentiation, and may be useful for research on new technologies to improve latex yield, and to screen for commercially useful phytohormones.     

Ultrastructure and Development of the Laticifers of Ficus carica L

Laticifers of Ficus caricaL. are of the branched, non-articulatedtype. They occur in the cortex and pith of the plant axis andpenetrate leaves and inflorescences. Observations were madeon laticifers located in shoot apices. Growing regions of laticifers undergo a sequence of ultrastructuralchanges. These are: (a) a pronounced increase in the vacuolarspace which divides the cytoplasm into separated masses; (b)a development of numerous vesicular structures in the cytoplasm.The vesicular structures are released into the vacuolar space.The whole process is accompanied by disintegration of cytoplasm.Apparently isolated masses of cytoplasm occur in the luminaof laticifer tips in sections taken from dormant apices. Itis assumed that these masses have a role in the initiation ofnew laticifer regions in the next growing season. Ficus caricaL., laticifers, ultrastructure, development differentiation     

Studies on Differentiation of Laticifers through Light and Electron Microscopy in Calotropis gigantea (Linn.) R.Br.

The distribution, cytological organization and differentiationof non-articulated laticifers in the primary and mature tissuesof Calotropis gigantea (Linn.) R.Br., were studied by the useof optical and electron microscopy. Laticifers occur in thecortex, vascular bundle and pith of the plant axis. At the earliestdetectable stage a laticifer is a cell which undergoes rapidelongation and nuclear division. This results in a multinucleateelongated cell which undergoes further increase in length withgradual degeneration of the cytoplasm. At the electron microscopiclevel the presumptive laticifer cell shows increasing vacuolationwhich forms a large central vacuole. Simultaneously the cytoplasmicorganelles undergo degeneration by autophagic processes. Laternumerous vesicles can be observed in the large central vacuole,the remaining cytoplasm being pushed to a thin layer. Maturelaticifers show three types of spherical structures of whichthe highly electron dense globules are the latex particles. Calotropis gigantea (Linn.), R.Br., laticifers, ultrastructure, differentiation     

Metabolism of 2-Chloroethylphosphonic Acid (Ethephon) in Suspension Cultures of Hevea brasiliensis

Suspension cultures of Hevea brasiliensis cells can metabolizethe growth regulator 2-chloroethylphosphonic acid to producea number of compounds, one of which appears to be an acid-labileconjugate. The general metabolic pattern closely resembles thatfound previously using Hevea leaves. Evidence that the compoundsformed are not chromatographic artefacts of a type describedby other authors is presented.     

STRUCTURE AND ONTOGENY OF LATICIFERS IN CICHORIUM INTYBUS (COMPOSITAE)

The branched anastomosed laticifer system in the primary body of Cichorium intybus L. originates in embryos from files of laticiferous members at the boundary between phloic procambium and ground meristem. Upon seed germination, laticiferous members develop perforations in the end walls which become entirely resorbed. Perforations also develop in the longitudinal walls of contiguous laticiferous members and from lateral connections between developing laticifer branches. Additional laticiferous members originate as procambium differentiation proceeds, and their differentiation follows a continuous acropetal sequence in leaf primordia of the plumule. In roots, laticifers closely associated with sieve tubes in the secondary phloem originate from derivatives of fusiform initials in the vascular cambium. These laticifers develop wall perforations and in a mature condition resemble laticifers in the primary body. As the girth of the root increases, laticifers toward the periphery, unlike associated sieve tubes, resist crushing and obliteration. Laticifers vary in width from about 4 to 22 μm; the widest ones occur in involucral bracts and the narrowest ones in florets. There was no evidence that intrusive growth occurs during development of the laticifer system, although such growth may occur during development of occasional branches which extend through ground tissue independent of phloem and terminate in contact with the epidermis. Presence of amorphous callose deposits is related to aging of laticifers and mechanical injury.     

Differentiation of Non-articulated Laticifers in Poinsettia (Euphorbia pulcherrima Willd.)

Differentiation of non-articulated laticifers in poinsettia(Euphorbia pulcherrima Willd.) was studied ultra-structurally.Growing laticifers show: (1) a multinucleate apical region containingabundant ribosomes but few other differentiated organelles and(2) a sub-apical zone where the cytoplasm is dominated by vacuolesof diverse morphology with latex particles. These particlesappear first within narrow tubular vacuoles developed especiallyin the peripheral cytoplasm. During vacuolation of the laticifer,portions of cytoplasm, including some of the nuclei, becomeisolated by the enlarging and fusing vacuoles; eventually thesebecome lysed, except the latex particles which remain in thecentral vacuole. During differentiation of a laticifer branch,the cytoplasm contains the usual organelles, including a fewmicrobodies and coated vesicles. The plastids that lie withinthe peripheral cytoplasm differentiate into amyloplasts witha single elongated starch grain. Towards the end of differentiationthe cytoplasm becomes restricted to a thin parietal layer, withthe remaining organelles reduced or degenerate, surroundinga central vacuole filled with latex particles. Euphorbia pulcherrima Willd, poinsettia, ultrastructure, differentiation, laticifers     

Ultrastructure and Differentiation of Protein-storing Cells in Secondary phloem of Hevea brasiliensis Stem

The ultrastructure and differentiation of the protein-storingcells in secondary phloem of terminal branchlets of Hevea brasiliensisMull. Arg. were studied using electron microscopy. The cellsare parenchyma tissue in the axial system and characterizedby the presence of a large amount of proteinaceous fibrils inthe central vacuole. The fibrils of the protein-storing cellsare straight, about 9 nm in diameter and arranged in a directionroughly parallel to the longitudinal axis of the stem. At theearly differentiation stage of the protein-storing cells, amass of proteinaceous fibrils appears in the cytoplasm, thenis separated from the peripheral cytoplasm by the endomembranesystem derived from endoplasmic reticulum, resulting in theformation of the central vacuole with the fibrils inside asthe vacuolar content The peripheral cytoplasm may continue toproduce proteinaceous fibrils with which the fibrils of thecentral vacuole is supplemented after the protein-storing cellsare formed. Hevea brasiliensis, storage protein, proteinaceous fibrils, vacuole, secondary phloem     

Anatomical and Histochemical Aspects of Bark Regeneration in Hevea brasiliensis

Natural rubber is obtained from the bark of Hevea brasiliensis.Both virgin and renewed bark are exploited for this purposeby a process known as tapping which involves controlled woundingand excision of bark tissues. The process of bark renewal andits nature and consequences thus assume importance. Anatomicaland histochemical changes encountered with tapping were thedeposition of lignin and suberin in the peripheral cells, enlargementof tray cells near the cut surface and the formation of a woundperiderm. In the course of development, the wound phellogenmade tangential continuity with the original phellogen in thevirgin bark and functioned as a single phellogen. Vascular cambialactivity was enhanced due to wound stimulus and the newly differentiatedsieve tubes and ray cells were larger in size. The first peridermwas functional for only a short period of time, after whicha new meristematic zone developed in the inner tissues. Virginand renewed bark differed in the proportion of soft and hardbark, amount and distribution of sclereids, tannin cells andcrystals.Copyright 1995, 1999 Academic Press Bark renewal, Hevea brasiliensis, histochemistry, laticifers, para rubber tree, wound periderm     

Effects of Jasmonic Acid and Ethephon on Tillering to Maturity in Spring Barley

Spring barley cultivated in Mitcherlich pots under both climaticchamber and field conditions were treated at developmental stageFeekes 2 with a foliar application of jasmonic acid (JA), itsmethyl ester (JAMe) and ethephon. Tillering was determined atFeekes 5 by counting all emerged tillers. The number of ear-bearingtillers, yield, and shoot length were ascertained at harvest.A combination of either JA or JAMe together with ethephon, appliedsimultaneously or successively (within 24 h), led to a significantincrease in tiller production. However, the additional tillerswere not sustained to maturity. Neither JA or JAMe nor ethephonalone were able to cause these effects at Feekes 2. JA seemsto increase the sensitivity to ethylene, possibly by influencingthe level of other native regulators. The JA/ethephon applicationat Feekes 2 did not affect the yield and the final shoot length. Spring barley, Hordeum vulgare L., tillering, apical dominance, plant growth regulators, ethephon, jasmonic acid     

Laticifer Differentiation of Calotropis gigantea R. Br. ex Ait. in Cultures

The initiation and subsequent development of laticifers werestudied in callus tissues of Calotropis gigantea grown on MS(Murashige and Skoog) medium supplemented with 1 mg l^–1IAA. Laticifer development was related to the age of the cultureand could be preserved by repeated subculturing on similar mediumwith IAA. Our previous work had established that cardenolidebiosynthesis was related to rhizogenesis and here we reportthe culture system of laticifer, long term preservation anddifferentiation of this hydrocarbon producing energy plant. Calotropis gigantea, Asclepiadaceae, laticifer, differentiation, cardenolides, tissue culture