ABSTRACT
The cytoskeleton is a dynamic three-dimensional architectural network in animal cells as well as in plant cells, and the microtubule (MT) cytoskeleton performs many important biological functions. Sensitivity to freeze-induced depolymerization of MTs was examined in chilling-insensitive plant species of spinach, beet, garlic, and wheat. Electron microscopy (EM) observations showed that MT density and length in root meristem cells of Azolla and maize were reduced after they were chilled. The evidences suggest that some degrees of insensitivity to freeze-induced depolymerization exist among chilling-insensitive plant species that have different cold hardiness. Abscisic acid (ABA) increases cold hardiness in many plant species. Sakiyama and Shibaoka reported that ABA was able to restore the MT cold stability, that was reduced by the GA3 pre-treatment, to the same extent of the stability in non-GA3-treated cells. Experiments with burst protoplasts revealed that cortical MTs are closely attached to plasmalemma. Microtubule-bridge-plasmalemma association may play an important role in stabilizing plasmalemma under stresses.
