Breaking Weight Research Articles

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.

Development of tensile strength in conventional and approach grafts in Sedum telephoides

Conventional autografts between severed internodes of Sedum telephoides attained a tensile strength of approximately 75 g breaking weight (BW)/mm2 graft area (GA) by 20 days after grafting. Approach grafts between cut surfaces were characterized by a tensile strength of approximately 42 g BW/mm2 GA by 10 days after grafting. Approach grafts in which membrane filters were inserted between the grafting surfaces attained a tensile strength of approximately 10 g BW/mm2 GA by 5 days after grafting. These results indicate that the cell wall deposition responsible for the initial cohesion of the stock and scion contributes approximately 13% of the tensile strength of the graft union in compatible Sedum autografts. Similarly, the interdigitation of callus cells and vascular redifferentiation (and the relatively small amount of wall deposition associated with each) contribute approximately 44 and 43%, respectively, to the tensile strength of the Sedum graft union. The data suggest synergistic interaction between different mechanisms of graft formation.

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.

Graft Formation inKalanchoe blossfeldiana

Three phases of cohesion between the stock and scion are observable during 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 the graft interface and with callus proliferation in the stock and scion, and (c) is characterized by a tensile strength of approximately 5 g breaking weight (BW) mm2 graft area (GA) by 5 d after grafting. The second phase of cohesion lasts from days 5 -20 after grafting and is correlated with (a) an interdigitation of callus cells at the graft interface, (b) the differentiation of vascular tissue across the graft interface, and (c) a 20-fold increase in the tensile strength of the graft union to approximately 100 g BW mm 2 GA by 20 d after grafting. This cohesive strength is comparable to that of an intact, non-grafted stem. The third phase of cohesion is characterized by a levelling off of the increase in tensile strength of the graft union with time at approximately 125 g BW mm2 GA. The results of this study are discussed relative to other structural studies of and proposed mechanisms for graft development.