THE DIFFERENCES OF SUBCELLULAR CA2+ DISTRIBUTION IN CUCUMBER SEEDLING LEAVES UNDER NO3- STRESS
The ultrastructural localization of calcium in cucumber seedling leaves was determined with the improved cytochemical method of calcium pyroantimonate precipitation, and the changes of calcium level in cells under NO3- stress were observed. After 7 d of treatment under optimum NO3- conditions, calcium antimonite deposits, which indicate calcium distribution, were mainly localized in intercellular spaces, cell wall and chloroplast, and smaller amounts of calcium precipitates randomly resided in plasma membrane and mitochondria. But under excessive NO3- stress, the distribution of Ca2+ in subcellular was changed greatly. Under 56, 98, 140 mmolL-1 of NO3- concentrations, Ca2+ level in cytoplasm and nucleus increased with the increases in NO3- concentration, due possibly to the opening of the channels in plasma membrane and tonoplast as well as the decrease or activity loss of the calcium pump. The increase of Ca2+ in the protoplasm might cause a series of disorders in metabolic processes. With the increasing NO3- concentrations, larger Ca2+ deposits localized on the envelope of plastid and Ca2+ were also deposited together in the intercellular spaces, while Ca2+ deposits were small and dense on the plasma membrane. In addition, Ca2+ accumulation in the mitochondria remained low and the shape and amount were also changed. Under 182 mmolL-1 NO3-, Ca2+ deposits in each compartment became smaller and denser, shacked tonoplast was not found, and Ca2+ in vacuoles was distributed closely to tonoplast. The possible relationship between the responsiveness of Ca2+ distribution in leaf cells and cucumber NO3- tolerance was discussed.
Yang, F.J., Wang, X.F. and Wei, M. (2008). THE DIFFERENCES OF SUBCELLULAR CA2+ DISTRIBUTION IN CUCUMBER SEEDLING LEAVES UNDER NO3- STRESS . Acta Hortic. 771, 197-206
cucumber seedling, NO3- stress, cytochemistry, Ca2+