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.     

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。     

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。     

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.     

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.     

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.     

<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 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。     

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。     

STUDIES OF VEGETATIVE COMPATIBILITY-INCOMPATIBILITY IN HIGHER PLANTS. IV. THE DEVELOPMENT OF TENSILE STRENGTH IN A COMPATIBLE AND AN INCOMPATIBLE GRAFT

Three phases of adhesion between the stock and scion are observable during the formation of a compatible autograft in Sedum telephoides and an incompatible heterograft between Sedum telephoides and Solanum pennellii. The first phase of adhesion is similar in both systems in that it 1) lasts 2 to 3 days, and 2) is characterized by an average increase in tensile strength of 1 g breaking weight (BW)/mm² graft area (GA)/day. In the compatible Sedum autograft, the second phase of adhesion lasts from Days 3 to 11 after grafting and is correlated with a 28-fold increase in the tensile strength of the graft union to approximately 56 g BW/mm² GA by 11 days after grafting. The third phase of adhesion in the compatible autograft is characterized by a leveling off of the tensile strength of the graft union at approximately 56 g BW/mm² GA, roughly equal to that of an ungrafted internode. Graft formation is now complete. These results suggest that the ratio of the tensile strength of the graft union : tensile strength of a comparable ungrafted internode provides an estimate of the percent development of compatible autografts. In the incompatible heterograft between Sedum and Solanum, Phase II adhesion 1) lasts from Days 2 to 5 after grafting, and 2) peaks at 12 g BW/mm² GA at 5 days after grafting. Phase III adhesion in the incompatible heterograft occurs subsequent to Day 5 after grafting and is characterized by an average decrease in the tensile strength of the graft union of 0.3 g BW/mm² GA/day. The results of this study are discussed relative to the quantitative contributions of various structural events to the tensile strength of a graft union.     

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。     

Graft formation in Solanum pennellii (Solanaceae)

Three phases of cohesion were observable during the development of compatible autografts in Solanum pennellii. Phase I cohesion 1) lasted 4–5 d after grafting, 2) was characterized by an average increase in tensile strength of 4 g breaking weight (BW) mm^–2 graft area (GA) d^–1, and 3) correlated positively with cellular interdigitation at the graft interface. The fresh weight of the scion increased by approximately 5% d^–1 during the first 2 d after grafting. Phase II cohesion occurred 5–15 d after grafting, during which time 1) the tensile strength of the graft union increased by 14 g BW mm^–2 GA d^–1, 2) vascular differentiation across the graft interface was completed, and 3) the fresh weight of the scion increased by 9% d^–1. Phase III cohesion occurred subsequent to 15 d after grafting, during which time 1) the tensile strength of the graft union leveled off at a value similar to that of an ungrafted internode, and 2) the fresh weight of the scion increased by 14% d^–1. These results are discussed relative to mechanisms underlying the formation of compatible grafts.     

Preliminary Studies on Controlling Graft Union Through Plant Hormones

The influences of IBA and 6-BA on the formation of grafting were studied by using explanted internode autografting of cucumber (Cucumis sativus) cultured in vitro, which was a simpler procedure for grafting with lower chance of contamination than the ordinary explanted internode grafting. Colour changes, root initiation and callus formation of the explanted internode graf related to the concentration of plant hormones added to the medium. Plant hormones controlled the formation of graft unions through influencing the time and the number of vascular bridges formation between the stock and the scion. In authors experiments, the optimal condition of plant hormone control was achieved when IBA 1.2 mg/L was added in the scion medium and 6-BA 0.3 mg/L was added to scion and stock medium.     

利用植物激素调控嫁接形成的初步研究

利用黄瓜（Ｃｕｃｕｍ ｉｓｓａｔｉｖｕｓ）试管苗进行离体茎段自体嫁接,研究ＩＢＡ 和６－ＢＡ 对嫁接形成的影响时发现：进行离体茎段嫁接时,用试管苗茎段可简化嫁接过程,减少污染。嫁接茎段的颜色变化、不定根发生和愈伤组织形成与激素浓度有关。植物激素通过影响砧木和接穗间维管束桥形成的时间和数目调控嫁接组合的发育。在作者的实验中,最佳的激素条件是：在接穗培养基中加ＩＢＡ １．２ ｍ ｇ／Ｌ,在接穗和砧木培养基中加６－ＢＡ ０．３ ｍ ｇ／Ｌ。     

植物嫁接愈合分子机制研究进展

嫁接能显著改良单一品种的产量、品质和抗逆等性状, 已广泛应用于农业生产。促进砧木和接穗在嫁接面的快速愈合有利于提高嫁接效率。目前对嫁接愈合调控机制尚了解不足, 因此短时间内难以进行有效的技术改良。嫁接愈合过程包括先后发生的创伤应激响应、愈伤组织形成、砧穗细胞通讯以及砧穗再生重连等生理事件, 均涉及复杂而交联的激素应答及基因调控模式。近年来, 相关领域的研究成果为综合解析嫁接愈合的调控机制奠定了基础。该文综述了在嫁接愈合过程中发挥核心作用的植物激素及其应答方式, 以及激素依赖或非依赖的基因表达调控模式, 以期为深入揭示嫁接愈合分子机制提供参考。     

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; )     

砧木与接穗间的电波传递

利用嫁接系统研究植物电波的传递表明：（１）无论砧木和接穗共质体连通与否,也无论在嫁接面上加琼脂与否,电波（ＥＷ）均能沿砧木向接穗传递;（２）砧木和接穗共质体连通之前,无论在嫁接面上加琼脂与否,ＥＷ不能沿接穗向砧木传递,砧木和接穗产生的愈伤组织细胞突破隔离层,互相嵌合,产生次生胞间连丝之后,ＥＷ可沿接穗传至砧木;（３）将枝条蒸腾流倒转后进行嫁接,ＥＷ可沿接穗（形态学上部,即插入水中部分）传至砧木（形态学下部）,但不能沿砧木传至接穗。