The Effect of a Grafted Bud on Vascularization of the Petiole in Phaseolus, Datura and Lycopersicon

The radially-organized petiole of Phaseolus and the dorsiventralpetioles of Datura and Lycopersicon were used as stocks in budgrafting. Petiolar structure was examined after some weeks'growth of the scion, during which the grafted petiole came tofunction as a stem in supporting normal, vigorous shoot growthand was not abscised even at the end of the growing season.Below the graft union, reactivated petiolar cambium producedmassive amounts of secondary tissue with greatly enlarged vessels.Cambial activity was confined to the existing vascular bundlesexcept for the development of a little inter-fascicular cambiumin young, grafted Phaseolus petioles. Datura petioles woundedbelow the graft union, by a cut into the petiolar are from eitherthe abaxial or the adaxial surface and removal of a 1 cm lengthof tissue, responded by restoring the vascular are (abaxialwounds) or almost completing a vascular ring (adaxial wounds).In grafted, wounded Lycopersicon petioles the presence of deadxylem caused the separation of cambium regenerated from thecut vascular are and that arising in relation to the centralwound surface. A similar response, in which stimulated internalphloem plays an important part, occurred in certain woundedLycopersicon stems. The results are discussed in terms of thegradient induction hypothesis. graft, petiole, wound, cambium, xylem, phloem, Phaseolus multiflorus, Datura stramonium, Lycopersicon esculentum, bean, thornapple, tomato     

<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> as a Model System for Graft Union Development in Homografts and Heterografts

Homografting of Arabidopsis thaliana scions on stocks of A. thaliana and heterografting on other species were used to study the compatibility and the ontogeny of graft union formation. Highly compatible homografting with scions of young leafy inflorescence stems was obtained on stocks of inflorescence stems growing from large 3-month-old A. thaliana plants. Histologic analysis revealed four developmental stages of graft union formation in Arabidopsis homografting: (1) development of a necrotic layer, (2) callus proliferation in the grafted scion, (3) differentiation of new vascular tissues within the scion, and (4) a full vascular graft union formation between the scion and the stock. Vascular connections were formed within the callus bridge between rootstocks and scions 15 days after grafting. Heterografts of Arabidopsis on two members of Brassicaceae, cabbage (Brassica) and radish (Raphanus), showed partial incompatible interaction with a lower level of vascular differentiation. Arabidopsis grafting on tomato (Solanaceae) rootstock showed complete incompatibility and limited noncontinuous differentiation of new vascular tissues that did not cross the scion/stock boundary. Although lacking scion/stock vascular connections, Arabidopsis scions grafted onto tomato rootstock flowered and produced seeds. This may indicate some nonvascular functional connections between the two plants, probably of parenchyma cells, further emphasizing the usefulness of Arabidopsis as a model plant for studying various levels of the complicated scion/stock relationships expressed in grafting biology. Experiments with dye transport in the xylem showed that although in general there was an agreement between the histologic study and dye transport, in Arabidopsis homografts water transport frequency was lower than functional and histologic compatability. We conclude that homografting and heterografting of Arabidopsis inflorescence stems is a convenient and reproducible method for studying the fundamental cellular genetic and molecular aspects of grafting biology.     

植物离体茎段嫁接

植物体茎段嫁接系统是在无菌条件下将茎切段嫁接后放入培养基中、使接穗和砧木分别与含不同成分的培养基接触,再署光下培养的一个模拟植物正常生理过程、环境条件可控的实验系统,离体茎段嫁接体的发育与整体类拟,包括接穗与砧木粘连、愈伤组织产生、次生甩间连丝形成和维管束分化等几个步骤,发育进程受植物激素如生长素和细胞分裂素调节。该系统的建立为阐明嫁接体发机理及嫁接亲和性机制提供了重要的依据。     

银杏愈伤组织的形成及其中黄酮类化合物的产生

单一激素种类对银杏叶片,叶柄和幼茎愈伤组织的诱导中以NAA的效果最佳,2,4－D次之,6－BA最差,除胚乳外,胚,幼苗的胚根,子叶,幼茎,叶片和叶柄,以及成年树的嫩茎,叶片和叶柄各外植体在本试验条件下都能诱发愈伤组织,其中胚,子叶和叶柄的愈伤组织形成频率均可达到100．0％,叶片和幼茎在光照下的愈伤组织诱导频率比黑暗中的略高,而叶柄和胚根则相反,MS和DCR两种培养基都适合银杏幼苗叶片及叶柄愈伤组织的诱导,两者之间不存显著性差异,测得光照培养的3个组织系（ST1,ST2,ST3)中均含银杏黄酮甙元槲皮素,山柰素和异鼠李素,总含量分别为干重的0．35％,0．29％和0．14％,而黑暗中培养的这3个愈伤组织系则没有银杏黄酮的产生。     

木犀属植物叶柄的比较解剖学研究

对木犀属(Osmanthus)26种植物叶柄的解剖结构进行了研究.结果表明,木犀属植物叶柄的解剖特征存在比较丰富的变异,叶柄横切面形状有3种类型(U型、V型、Y型),周缘波状、浅波状或近平滑;表皮毛有或无;维管束一般为1大2小,维管束轮廓在种问变异丰富,维管束类型有周韧、近周韧、外韧3种;小叶月桂、牛矢果、厚边木犀、美洲木犀叶柄中央具髓腔,部分种叶柄有硬化细胞或石细胞存在.木犀属植物叶柄的解剖结构特征比较稳定,可作为该属的分种特征.     

Callus Formation at Graft Interface in Ginkgo biloba L.

The early stages of graft union, when male branch was grafted onto female branch in Ginkgo biloba L. by cleft graft, have been observed under light microscope in order to determine the origin of callus cells between the stock and scion. Pith parenchyma cells near the graft interface were the earliest cells in response to such method of grafting. These cells dedifferentiated and then divided within 7～ 12 days after grafting. A large number of callus cells extended from the pith into the space between the graft interface linking the stock with the scion about 18～ 20 days after grafting; and then continued to proliferate and extend outwards along the space. Cambium cells and immature vascular tissue near the graft interface dedifferentiated into callus rather late. Theover all link between the stock and scion was completed in the sites 30 days after grafting. Callus cells were also produced from corticai parenchyma cells, but they were much limited in quantity. In conclusion, the graft interface may be considered as a "natural culture bed" after grafting, in which all undamaged, living cells are capable of dedifferentiation and producing callus cells for compatible graft union. In the case of G. biloba (male/female) it were the pith parenchyma cells that appeared first to form the callus cells and later extend to link the stock with the scion.     

葡萄属营养器官的比较解剖学及其系统学意义

本文对国产葡萄属24个种、6个变种和4个美洲种进行了比较解剖学研究。比较观察了茎、节、 叶柄、叶片的维管系统、厚角组织、厚壁组织、毛状体、后含物、叶表皮角质等解剖学特征。并讨论了它们在系统学上的意义。     

VASCULAR BUNDLES IN PETIOLES OF SOME HERBACEOUS AND WOODY DICOTYLEDONS

Structure and distribution of vascular bundles (VB) have been investigated in petioles of 26 herbaceous and woody dicotyledons. No single pattern of vascular bundle distribution could be found for both groups of plants. Both groups of plants had VB patterns ranging from a cylinder to separate bundles arranged in a variety of patterns, e.g., distorted cylinder, various configurations of a crescent, and other types. The total number of xylem vessels in herbaceous and woody plant petioles varied between 110 and 1756.     

Auxins and cytokinins exuded during formation of roots by detached primary leaves and stems of dwarf French bean (Phaseolus vulgaris L.)

Summary Hypocotyls of detached stems standing in culture solution produced adventitious roots sooner than did petioles of detached primary leaves. An auxin, probably indol-3-ylacetic acid, appeared in the solutions before the hypocotyls or petioles produced roots. After attaining a maximum, the amounts of auxin in the solutions decreased as fewer roots were formed. Two cytokinins were found in the culture solutions; one had a similar R_f to zeatin, the other ran more slowly on chromatograms. The amounts of cytokinin in the solutions were associated with root formation. Stems soon died unless their hypocotyls formed roots, but the primary leaves survived without roots forming provided a callus formed on the petiole. Hence adventitious roots, or callus tissues, may have produced cytokinins that replaced those produced by the original roots, found in sap exuded from the stem stumps, and were essential for survival of the stems and leaves.     

Transformation by Agrobacterium tumefaciens Changes Graft Compatibility of Tissues of Nicotiana tabacum L.

Abstract Shoots, callus or tumor tissues of N. tabacum have been grafted to stock plants of different species of Solanaceae. The graft compatibility ranges of the three grafted tissue types were different. For example; shoots of N. tabacum united easily with root-stocks of Lycopersicum esculencum. Tumors of the same variety of N. tabacum transformed by different strains of Agrobacterium tumefaciens did not produce transplantation tumors on L. esculentum. These results are discussed with respect to recognition events at the graft contact zone.     

In Vitro Shoot Regeneration from Callus, Leaf Axils and Petioles of Sugar Beet (Beta vulgaris L.)

Procedures are described for producing axillary shoots fromseedling apices and adventitious shoots from petioles and leaf-derivedcallus of sugar beet cultivars. The rate of adventitious shootregeneration from petioles was influenced by temperature, BAPconcentration of the medium, and the time in culture of theseedling apices from which the petioles were excised. Petiolesectioning confirmed that adventitious shoots originated inthe sub-epidermal parenchyma. Two distinct types of callus wereproduced from leaf explants, but only white friable callus wascapable of shoot development. This callus developed from browntissue and was composed of thin-walled cells with dense cytoplasmand prominent nuclei. Green compact callus with thick-walledlignified cells developed from green tissue, but did not produceshoots. Successful seed sterilization and shoot regenerationfrom petiole explants and callus was cultivar-dependent. Adventitiousshoots were rooted and successfully transplanted to pottingcompost under glasshouse conditions. Key words: Adventitious shoots, axillary shoots, callus, sugar beet (Beta vulgaris L.)     

小桐子愈伤组织的诱导

本文以小桐子的叶片、叶柄、茎段及下胚轴和子叶作为外植体,研究不同外植体类型对愈伤组织诱导的影响,结果表明叶柄的诱导率最高,其次为茎段的诱导率。同时以小桐子的下胚轴作为外植体,研究植物生长调节剂种类及浓度配比对愈伤组织诱导的影响,结果显示6-BA与2,4-D的组合更适宜小桐子愈伤组织的诱导,MS+6-BA0.5mg/L+2,4-D0.1mg/L为小桐子愈伤组织诱导的最佳培养基,其愈伤组织诱导率高达96.7%。本研究为小桐子愈伤组织的分化、植株再生及相关的遗传转化研究提供了参考。     

TISSUE RESPONSE TO PALLADIUM MICROPROBE,AS OBSERVED IN GOSSYPIUM HIRSUTUM L. (MALVACEAE)

Small (250 μm diam) palladium microprobes, either sharpened or blunt-tipped, were inserted into peduncles and petioles of field-grown cotton (Gossypium hirsutum L. cv. ‘Deltapine 61‘). Two weeks after microprobe insertion, tissue was harvested and processed for subsequent light-microscopic examination. Factors which influence structure and organization of wound response tissue, such as developmental stage of tissue at microprobe implantation site, are discussed. Patterns of differentiation in the wound response tissue which surrounds the microprobes are illustrated. There appeared to be direct rather than peripheral continuity between normal vascular tissue and vascular tissue formed within the wound callus surrounding microprobes implanted in petiole and peduncle. Apparently restoration of direct vascular connections between the original vascular tissue and the vascular tissue formed within the wound callus is a characteristic wound-healing response following microprobe implantation in cotton.     

Studies on graft unions

Summary The occurrence of plasmodesmata in the graft interfaces of two heteroplastic grafts (Impatiens walleriana onImpatiens olivieri andHelianthus annum onVicia faba) has been studied. For both systems two types of intercellular strand are described: 1. Continuous plasmodesmata interconnecting the cells of stock and scion and 2. half plasmodesmata traversing the wall part of one partner cell without connection to the abutting cell. Single strands or branched forms occur in both types of plasmodesma. In the case of half plasmodesmata, branchings with extended median nodules predominate. The distribution of half and continuous plasmodesmata varies with the different areas of a graft interface: in the region of bridging vascular tissues most cell connections are continuous. In areas where cortex or pith-derived callus cells and those of misaligned tissues (cortex/vascular tissue; cortex/pith; pith/vascular tissue) match, discontinuous strands predominate.Branched half plasmodesmata also occur in presumably fused walls between related callus cells; they are typical structures secondarily formed in non-division walls.The results are discussed with regard to compatibility/incompatibility phenomena in heterografts and the development and function of interspecific cell bridges.     

Tissue-Specific Expression of Cell Wall Proteins in Developing Soybean Tissues

Cell wall hydroxyproline-rich glycoproteins (HRGPs) and glycine-rich proteins (GRPs) were examined at the protein and at the mRNA levels in developing soybean tissues by tissue print immunoblots and RNA blots. In young soybean stems, HRGPs are expressed most heavily in cambium cells, in a few layers of cortex cells surrounding primary phloem, and in some parenchyma cells around the primary xylem, whereas GRPs are highly expressed in the primary xylem and also in the primary phloem. In older soybean stems, HRGP genes are expressed exclusively in cambium cells and GRP genes are most heavily expressed in newly differentiated secondary xylem cells. Similar expression patterns of HRGPs and of GRPs were found in soybean petioles, seedcoats, and young hypocotyls, and also in bean petioles and stems. HRGPs and GRPs become insolubilized in soybean stem cell walls. Three major HRGP mRNAs and two major GRP mRNAs accumulate in soybean stems. Soluble HRGPs are abundant in young hypocotyl apical regions and young root apical regions, whereas in hypocotyl and root mature regions, soluble HRGPs are found only in a few layers of cortex cells surrounding the vascular bundles. GRPs are specifically localized in primary xylem cell walls of young root. These results show that the gene expression of HRGPs and GRPs is developmentally regulated in a tissue-specific manner. In soybean tissues, HRGPs are most heavily expressed in meristematic cells and in some of those cells that may be under stress, whereas GRPs are expressed in all cells that are or are going to be lignified.     

Graft establishment between compatible and incompatible Prunus spp

Graft compatibility has been studied in apricot (prunus armeniacaL.) grafted on Prunus cerasifera Ehrh. Two apricot cultivars,one compatible and one incompatible on this rootstock, wereselected for this study. In these species incompatibility isonly manifested by tree breakdown at a late phase of the tree'slife. The process of graft union formation was observed forthe first month following grafting. No differences were foundeither in the process of healing or in its kinetics. Thus, callusproliferation, callus differentiation and vascular connectionsare established in the same way and at the same time in bothcompatible and incompatible grafts. However, clear differencesexist in the level of differentiation of the callus produced.While in compatible grafts, callus quickly differentiates intocambium and vascular tissue, in incompatible grafts this differentiationis not complete and a portion of the tissue evolves into a parenchymatoustissue that coexists with the differentiated vascular tissue. Key words: Graft, Prunus, compatibility     

The position of regenerating cambia: auxin/sucrose ratio and the gradient induction hypothesis.

To account for the positions in which vascular cambia regenerate in wound callus, a gradient induction hypothesis was proposed in 1961 in terms of gradients in 'some factor as yet unknown'. It now seems likely that the gradient is based on morphogen diffusion between source and sink on opposite sides of existing cambia, with morphogen diffusing into the adjoining wound callus. It is specifically proposed that there are two morphogens, auxin diffusing centrifugally and sucrose diffusing centripetally. The cambium then regenerates along a path where the ratio of auxin to sucrose concentration is similar to that at the original cambium, and its orientation (as regards xylem and phloem formation) is determined by the direction of the gradient in this ratio. These proposals are supported by published evidence on auxin and sucrose concentration gradients across the cambium, and on their sources, movements, and known effects on vascular differentiation. Simulations of the proposed positional control system predict patterns of cambial regeneration and orientation corresponding to those observed in four different types of wound and graft.     

The Formation of Adventitious Roots and Buds in the Petiole of Detached Leaf of Pelargonium Graveolens

Median sized leaves of Pelargonium graveolens L'Her. after being excised from the middle of the petioles were planted in quartz sand or common sand in greenhouse. After one week in culture, calluses were formed aberrantly at the wound surface of the petioles of most of the detached leaves. By the second week, adventitious roots initiated somewhere in the callus close to the vascular tissue of the splitted base of the petiole. Adventitious buds also initiated from the callus, but they were not related to the vascular tissue in the origin. There were two different modes of initiation: one from the depth of the callus (endogenous) and the other near its surface (exogenous). Soon after, the distal end of the bud primordium became flattened (most of them became inverted triangular in outline) as was seen in the longitudinal section. Later, the middle part of the distal end became depressed and differentiated into the first leaf primordium and the apical meristem. As the young bud became further elongated, the leaf primordia were consecutively formed. Consequently the structure of the adventitious buds approached normal. The apical portion emerged from the sand was similar to the mature one in structure.     

南瓜属植物离体茎段嫁接维管组织的发育过程

在离体条件下,采用同瓜属植物的下胚轴节段进行嫁接,光镜观察发现：异种嫁接西葫芦／南瓜和南瓜自体嫁接嫁接后６－８ｄ在接穗、砧木的薄壁细胞和嫁接面处愈伤组织细胞中分化出管状分子和筛分子,边接接穗和砧木的质部和韧皮部桥在嫁接后８ｄ形成。随后随发育天数的增加其数目增加,用６（５）ＣＦ作为筛管输导的示踪剂检验了不同发育时期砧木和接穗间的连通情况,发现嫁接后８ｄ从接穗引入的６（５）ＣＦ可以输导到砧木。