REGULATION OF INTRACELLULAR MOVEMENTS IN PLANT-CELLS BY ENVIRONMENTAL STIMULI

This chapter describes regulation of intracellular movements in plant cells (cytoplasm, chloroplasts, and nucleus) by environmental stimuli (light, low temperature, wounding, and chemicals). It also reviews possible receptor systems specific for each type of environmental stimulus, a motile apparatus that functions as a specific effector, and a possible signal-transduction chain that conveys information between a receptor system and an effector system. In plant cells, various forms of intracellular movements such as the orientation movement of chloroplasts, the traumatotactic or premitotic migration of the nucleus, and streaming of the cytoplasm, are observed. These movements are thought to be essential for accomplishment of efficient photosynthesis, cell division at a suitable site, and appropriate delivery of substances that are required for growth and differentiation of plant cells. A spatially well-organized motile apparatus drives these movements in plant cells. When streaming is induced by light irradiation, the streaming is referred to as photodinesis. The distribution of organelles in the cytoplasm does not change after the perception of light and the response is independent of the direction of irradiation. For cytoplasmic streaming to occur, at least two conditions must be fulfilled— a motive force must be generated and the cytoplasmic matrix must have appropriate mechanical properties. Streaming of the cytoplasm can be accelerated through an increase in the motive force or a decrease in the cytoplasmic viscosity. © 1993, Academic Press, Inc.