Studies of vegetative compatibility–incompatibility in higher plants. V. A morphometric analysis of the development of a compatible and an incompatible graft

Abstract

A morphometric analysis of graft development in (i) the compatible autograft in Sedum telephoides, and (ii) the incompatible heterograft between Sedum telephoides and Solanum pennellii was performed to characterize ultrastructural responses of grafting cells in compatible and incompatible unions. In the compatible autograft, relative volume of hyaloplasm (in the protoplasm) increases 750% by 3 days after grafting. This increase in hyaloplasmic volume is accompanied by a 61% decrease in relative volume of the vacuome during the same period. Relative volume of dictyosomes (in the protoplasm) increases fourfold during the first 8 h after grafting. Relative volumes of mitochondria, endoplasmic reticulum, nuclei, and nucleoli increase less dramatically during early stages of graft development. The time required to reestablish control (i.e., 0 h) volumes for these organelles is quite variable, ranging from 7 days for dictyosomes to 28 days for the vacuole and hyaloplasm. These results indicate that the intensity and duration of the responses of cellular components to the wound recovery associated with a compatible graft union are organelle specific. In the incompatible heterograft, the responses of all cellular organelles (except nuclei and components of the endomembrane system) are similar to that of the compatible autograft through the first 24 h after grafting. By 3 days after grafting, however, nuclei and components of the endomembrane system exhibit significantly lower relative volumes in the incompatible heterograft than in the compatible autograft. Therefore, nuclei and components of the endomembrane system are the first cellular components to exhibit signs of cellular incompatibility during graft formation in the incompatible heterograft between Sedum and Solanum.