Impact of Drought Stress on the Ultrastructure of Leaf Cells in Three Barley Genotypes Differing in Level of Drought Tolerance
干旱胁迫对不同耐旱性大麦品种叶片超微结构的影响

We examined 3 barley genotypes differing in level of drought tolerance in terms of structural differences at the subcellular level. The subcellular structure did not differ among the 3 genotypes under non-stressed conditions, but nuclei, chloroplasts and mitochondria of leaf cells of all 3 genotypes showed ultra-structural changes after drought stress treatment. In the drought-sensitive genotype Moroc9-75, drought stress caused a high degree of chromatin condensation, altered chloroplast conformation with the waving/swelling of the outer membrane of the chloroplast envelope, and disrupted thylakoids that showed conformational and configurational alterations. In addition, the structure and membrane of the mitochondria was disrupted, and cristae partially disappeared. In the drought-tolerant genotype HS41-1, water shortage caused lighter chromatin condensation than in Moroc9-75, and after drought stress, most chloroplasts and mitochondria in leaf cells showed no significant changes in conformation or configuration. Martin possessed moderate tolerance to drought, and its response to water deficit was between that for HS41-1 and Moroc9-75. Therefore, drought tolerance in barley is related to chloroplast shape, the integrity of grana and stroma thylakoids in chloroplasts and their regular arrangements, the degree of chromatin condensation, and the integrity of mitochondria and cristae. These ultrastructural traits could be used as structural indexes for evaluating drought tolerance in barley.