The resistance to anoxia and the mitochondrial fine structure of rice seedlings

Summary

Under anoxia, rice coleoptiles have a remarkable capacity to grow and to preserve undamaged mitochondrial structure and functions. The transfer of aerobically grown intact seedlings to anaerobic conditions resulted in the appearance of unusual mitochondria in coleoptiles as well as in leaves and roots. These mitochondria become filled with stacks of extended cristae, but, obviously, are not affected structurally (only in the root cortex the cells are damaged after a longer period without oxygen). On the contrary, the mitochondria and other organelles of excised coleoptiles, roots and leaves disintegrate after a relatively short exposure to an oxygen-free environment. The degeneration can be avoided if the excised organs are supplied with glucose. Then the mitochondrial fine structure resembles that of intact plants kept under anaerobic conditions.

The observations suggest that the capacity of rice coleoptiles to grow under anoxia and to preserve undamaged mitochondria and other organelles is not caused by the resistance of the cell organelles to oxygen deficiency, but rather by the ability of the seedling to transport organic compounds easily, even under the exclusion of oxygen, from the grain to the coleoptile where they can be utilized by glycolysis.