Effects of desiccation on the subcellular matrix of the embryonic axes of Quercus robur.

Abstract

The effects of desiccation on the ultrastructure of Quercus robur embryonic axes isolated from intact seeds that had been dried to various nominal water contents were investigated. Root meristem tissues were prepared for conventional transmission electron microscopy and the microtubule and microfilament systems were visualized using specific probes and fluorescence and confocal microscopy. The axes of this species were able to withstand some desiccation in that drying from 55% to 40% water content had little effect on viability. This was supported by the overall ultrastructure, and microfilament and microtubules systems of this material appearing similar to the control. Drying to 35% caused a 40% decline in viability. At the ultrastructural level such axes were characterized by plasmalemma withdrawal from the cell wall, cytoplasmic clearing between the endoplasmic reticulum sheets and nuclear lobing. At this water content, the number of cells in which the microfilament and microtubule systems could be demonstrated declined, and this important cytoskeletal system did not reconstitute to control levels on imbibition. Drying to below 35% caused drastic losses in viability and ultrastructural disruption.