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。     

A Study of the graft union in in vitro micrografted apple

Light microscopy was used to study graft union formation in in vitro micrografts of tissue cultured apple (Malus domestica. Borkh). Micrografts were constructed using horizontal incisions to form the grafting surface, and placing the cut ends of rootstock and scion into sterile silicon tubing to permit graft formation to occur.The outer morphological and histological development was similar for different stock-scion micrograft combinations but graft union formation was slower in heterografts than in autografts. Initial leaf expansion at the scion shoot apex occurred in all micrografted plantlets within 1–4 days and was not indicative of graft success. Progressive scion growth and development could be used as an indication of graft success by ten to fourteen days after grafting and probably was related to establisment of cell to cell contact at the graft interface. Microscopy showed initiation of callus proliferation in the vascular cumbium and the pith ten days after grafting. Differentiation was observed subsequently and this was reflected in scion development. Longitudinally orientated cambial cells began to differentiate between twenty and forty days after grafting, and formed a bridge between the vascular cylinders of scion and rootstock. The scions at this stage had as many as eight newly expanded leaves and micrografts were strong enough to permit silicon sleeve removal without damage. Continuity of new vascular elements in rootstock and scion was established around forty days. New vascular elements curved slightly in towards the pith to form a c shaped bridge across the graft union. Vascular development continued until it reached completion after six months.     

STUDIES OF VEGETATIVE COMPATIBILITY-INCOMPATIBILITY IN HIGHER PLANTS. I. A STRUCTURAL STUDY OF A COMPATIBLE AUTOGRAFT IN SEDUM TELEPHOIDES (CRASSULACEAE)

Initial adherence of the cut surfaces occurred by 24 hr after grafting and was correlated both with a pronounced dictyosome activity along the graft interface and with callus proliferation in both the stock and scion. A necrotic layer of one or two collapsed cells in thickness initially extended as a continuous barrier between the stock and scion, but the layer was fragmented by 2–3 days after grafting as the callus proliferation continued. Graft incision also induced a mild senescence in cells at the graft interface characterized by a reduced staining intensity of the cytoplasm, replacement of the large primary vacuole by numerous smaller vacuoles, and the occurrence of flocculent material throughout the cytoplasm. Starch accumulated during the first day after grafting but disappeared by 2–3 days after grafting. The cellular senescence never proceeded beyond an early, nonlethal stage, and cells along the graft interface completely recovered by 3 wk after grafting. Procambial differentiation occurred across the callus bridge by 10 days after grafting, and mature vascular continuity was established by 14 days. The results of this study are discussed relative to cellular recognition phenomena and to proposed mechanisms for plant graft compatibility-incompatibility.     

电波传递在嫁接基本理论研究中的应用

研究发现电波从接穗跃过嫁接面向砧木传递与嫁接的组织学变化相关。砧木和接穗愈伤组织细胞突破隔离层互相嵌合之前,接穗中产生的电波不能传到砧木。砧木和接穗细胞间产生次生胞间连丝后,电波即可沿接穗传至砧木,但此时传递速度慢。当砧木和接穗间产生维管束桥时,电波下传的速度加快。由此可见,通过检测电波跃过嫁接面与否及下传的速度,就可推断嫁接接合部组织学变化状况。电波传递法是一种快速鉴定嫁接植株发育过程的新方法。     

Application of Electrical Wave Transmission in Basic Research of Grafting

Electrical wave (EW) transmission from scion to stock across the grafting interface was related to the histological changes during the development of graft union. Variation wave (VW) could not be transmitted to stock from scion before isolation layer broken and callus interdigitation. As plasmodesmata formed secondarily at the interface between stock and scion where the isolation layer had disappeared, VW could be transmitted from scion to stock, but its velocity was not rapid until the vascular bridges form between two partners of graft union. Hence, the authors could deduce the degree of graft union formation by measuring whether VW could be transmitted from scion to stock or not and its velocity. EW trans mission method was a new tool for quickly detecting the formation of graft union.     

油茶芽苗砧嫁接口愈合过程解剖学研究

采用石蜡切片法对油茶（Camellia oleifera）芽苗砧嫁接口的愈合过程进行组织解剖学研究。观察结果表明：（1）在嫁接后的第4天,嫁接口产生隔离层;在嫁接后的第8天,嫁接口的砧木产生愈伤组织;在嫁接后的第16天,嫁接口的接穗产生愈伤组织;在嫁接后的第22天,嫁接口的砧木与接穗连接;在嫁接后的第29天,嫁接口的形成层分化形成;在嫁接后的第35天,嫁接口的愈伤组织维管束形成,接穗连接成功。（2）油茶芽苗砧嫁接部位愈伤组织形成前,芽苗砧木的解剖结构在短时间内加速发育,逐渐与接穗的组织结构相似。（3）嫁接口的形成层和其它薄壁细胞组织均能产生愈伤组织,但形成层是其主要来源。     

翅果油树茎段愈伤组织和芽发生的组织学研究

本文对翅果油树大宫灯型茎段培养在ＭＳ附加６－ＢＡ较高、ＮＡＡ较低浓度的培养基上培养０～３０ｄ的组织学变化进行了研究。创伤对其愈伤组织的形成有明显的刺激作用,培养３～４ｄ切口处的皮层细胞、形成层细胞、韧皮部薄壁细胞以及髓组织细胞,甚至表皮细胞均脱分化开始分裂;培养８～１１ｄ,切口明显膨大,起源于髓及维管组织周围薄壁细胞的愈伤组织突起大;培养１２～２０ｄ愈伤组织块中出现了分生组织和维管组织结节;培养２１～３０ｄ,愈伤组织表层和近表层细胞分化出芽原基,但与维管组织结节无直接联系。     

<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.     

Graft Formation in Kalanchoe blossfeldiana

Three phases of cohesion between the stock and scion are observableduring the formation of compatible autografts in Kalanchoe blossfeldiana.The first phase of cohesion: (a) lasts four to five days, (b)is correlated with an accumulation of dictyosomes along thegraft interface and with callus proliferation in the stock andscion, and (c) is characterized by a tensile strength of approximately5 g breaking weight (BW) mm^–2 graft area (GA) by 5 d aftergrafting. The second phase of cohesion lasts from days 5–20after grafting and is correlated with (a) an interdigitationof callus cells at the graft interface, (b) the differentiationof vascular tissue across the graft interface, and (c) a 20-foldincrease in the tensile strength of the graft union to approximately100 g BW mm^–2 GA by 20 d after grafting. This cohesivestrength is comparable to that of an intact, non-grafted stem.The third phase of cohesion is characterized by a levellingoff of the increase in tensile strength of the graft union withtime at approximately 125 g BW mm^–2 GA. The results ofthis study are discussed relative to other structural studiesof and proposed mechanisms for graft development.     

Graft Formation in Sitka Spruce: A Scanning Electron Microscope Study

Low-temperature and conventional scanning electron microscopyhave been used to examine the callus formed at the graft interfacein Picea sitchensis (Bong.) Carr. Callus cells are producedby both cambium and ray parenchyma dedifferentiation and redifferentiationin scion and stock. Adhesion between the cells derived fromscion and rootstock is thought to be my means of pectinaceousbeads at the surface of the callus cells, preceding a more generalfusion of cell walls. The cambia of the two graft componentsare prevented from growing towards each other by the presenceof callus. Instead, the differentiation of new cambium withinthe callus, in the vicinity of the cambia exposed at the preparedsurfaces of the scion and rootstock, links them to form a continuouscambial layer around the combined stem. Callus, cambium, differentiation, grafting, Picea sitchensis     

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。     

The Function of Phloem Connections in Regenerating In Vitro-Grafts*

In order to answer the question whether functioning phloem connections exist between graft partners, phloem transport has been studied in cultured explant-grafts after application of ¹⁴C-sucrose and carboxyfluorescein (CF) to the scion. Autografts of Lycopersicon esculentum and Helianthus annuus were investigated at various regeneration periods. Ungrafted internodes served as controls. A segmental analysis was used to determine the tissue distribution of ¹⁴C-sucrose in a graft. The ¹⁴C-profiles obtained show that sucrose translocation across the graft interface started 4 days after grafting and increased later. The observed translocation appears to occur via wound phloem, since at this time the first complete wound-phloem bridges (shown as files of aniline-blue-positive sieve plates) traverse the graft interface. In 7-d-old autografts, sucrose transport across the graft interface returned to normal again, as indicated by the distribution of the label. In addition, ¹⁴C-profiles reveal accumulation of label in sink tissues. Here the basal callus of the stock, and temporarily the graft union itself, represent the main sinks for labelled sucrose. Translocation of CF was analyzed in hand sections of the grafts. The beginning of translocation into the stock was confirmed with the dye. Moreover, effective phloem translocation across the graft interface, visualized with CF, could undoubtedly be assigned to wound-phloem bridges reconnecting the cut vascular bundles of scion and stock. Thus, the function of phloem connections in regenerated in vitro-grafts is directly shown.     

巴西橡胶树嫁接接合区接穗和砧木径向生长差异的研究

采用树皮嫁接后不锯砧和光镜观察的方法,研究了巴西橡胶树(Hevea brasiliensis)嫁接后8个月的接合区接穗和砧木木质部径向生长的差异现象。结果表明,接合区接穗木质部的径向生长普遍地小于砧木,这种生长差异是由接穗和砧木亲本固有生长特性的差异引起的,与嫁接亲和性无关。(1)对于同一无性系,接穗的发育阶段决定其生长能力,幼态接穗新分化的木质部显著地大于老态接穗,而两类接穗旁边的砧木之间没有明显差别。(2)砧木生长势明显地影响接穗木质部的生长,砧木生长势越强,砧木和接穗的生长就越快,两者的径向差异也越大。(3)同一砧木上各品系接穗木质部生长差异取决于接穗自身的生长特性,砧木的生长不受接穗品系的明显影响。显微观察表明橡胶树的嫁接是亲和的,接穗新分化的木质部镶嵌在砧木新分化的木质部中,维管组织如导管上下连接畅通,砧穗树皮厚度一致,愈合良好。     

Prevention of auxin-induced vascular differentiation in wound callus by surface-to-surface adhesion between calluses of stock and scion in cactus grafts

The relationship between formation of CVB, which connects vascularcut ends of stock and scion, and the condition of tissue whereCVB is expected to be induced was studied using a cactus graftcombination of Notocactus submammulosus var. pampeanus youngseedlings on Hylocereus trigonus plants. When a scion with its basal part removed by a transverse cutwas put onto a transverse cut surface of a stock with a distanceof 1 mm between the vascular cut ends of both graft components,CVB was formed in only 13% of the grafts in the callus massmade by adhesion between calluses of stock and scion. The percentagearose to ca. 100% when 100 ppm NAA was applied to the scionapices. This promotive effect of NAA decreased with increasingtime from grafting to NAA application. When wound calluses of stock and scion were prevented from contactonly at the portion between the vascular cut ends of stock andscion by introducing a piece of aluminium foil into the graftunion, CVB was formed in 80% of the grafts in the callus ofthe stock without NAA application. In the case where the scionwas grafted at right angle onto an additional longitudinal cutsurface made 1 mm from the vascular bundle of the stock withremaining intact parenchyma between this cut surface and thevascular bundle of the stock, CVB was not formed even when NAAwas applied. These results suggested that wound response wasa prerequisite for CVB differentiation and that surface-to-surfaceadhesion of calluses inhibited CVB formation by making calluscells differentiate into quiescent parenchyma cells rapidly.The mechanism of this phenomenon is discussed. (Received September 29, 1977; )     

Studies on graft unions. I. Plasmodesmata between cells of plants belonging to different unrelated taxa

Summary In order to answer the question whether plasmodesmata exist between the cells of stock and scion in a graft union of higher plants, a heteroplastic graft has been selected with species-specific cell markers.Vicia faba was used as scion andHelianthus annuus as stock. In the mixed callus of the graft union, individual cells of the two partners differ in the structure of the nuclei, plastids and microbodies. In the fused cell walls betweenVicia andHelianthus cells, plasmodesmata interconnect the protoplasts of the unrelated cells. Two types of plasmodesma occur: single strands and branched connections. The fine structure of the interspecific cell bridges, which have been secondarily formed in non-division walls, is similar to that of normal plasmodesmata in division walls. Some questions concerning compatibility/incompatibility in the heterograft are discussed.     

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.     

Early detection of graft incompatibility in apricot (Prunus armeniaca) using in vitro techniques

Graft compatibility has been studied in vitro using callus tissues of apricot ( Prunus armeniaca) and different Prunus rootstocks to form scion/rootstock combinations with different degrees of graft compatibility. In these species, incompatibility is manifested by a breakdown of the trees at the union area that can occur some years after grafting. Here, the possibility of obtaining an early detection method to determine graft incompatibility is explored by callus fusion in vitro. The adhesion of the two callus partners, the development of the cells at the contact surface (cell arrangement, intensity of cell-wall staining), and the presence of lipid and phenolic compounds have been studied during the first 3 weeks after grafting in both compatible and incompatible combinations. Differences were observed at the second and the third week of callus co-culture in most of the characters determined, although these differences were present as early as the first week in the case of phenolic compounds. The behaviour of the grafts grown in vitro was correlated to that of the same combinations in the field, suggesting that callus fusion in vitro could be a possible and reliable method for an early detection of graft incompatibility in different Prunus combinations.     

Establishment, graft union characteristics and growth of Prunus micrografts

A micrografting technique for use on shoots derived by shoot-tip culture is described. Autografts of Prunus domestica cv. Hauszwetsche as well as heterografts of several sour cherry cultivars ( Prunus cerasus L. cvs Schattenmorelle, Weiroot 158, Köröser) were established. Successful graft formation in vitro was confirmed by translation of ⁸⁶Rb⁺ from the stock root into growing scion tissues. A mechanically strong graft union was formed during the course of a 3-week subculture of micrografts in a liquid medium without the addition of growth regulators. In the case of graft rejection, ⁸⁶Rb⁺ was mainly attracted to new developing shoots from lateral meristems of the stock plant. Histological examination of the graft union revealed callus formation, cytodifferentiation and xylogenesis leading to the formation of vascular connections. Stem elongation after micrografting was related to vigour of the stock and scion genotypes. Early stem elongation could be used as a criterion for preselection of growth vigour in graft combinations. Micrografts were transferred to soil and grown in the greenhouse.