The dynamic changing of Ca2+ cellular localization in maize leaflets under drought stress.

Maize cultivar zhengdan958 was selected as materials. The sub-cellular distribution of soluble calcium at different phases was shown by the potassium-pyroantinonate-precipitation method and transmission electron microscopy. The results showed that the deposits of calcium antimonate as the indicator for Ca(2+) localization were mainly concentrated within the vacuoles and intercellular spaces without PEG treatment. Firstly, when the leaf was treated with PEG, the Ca(2+) level increased remarkably in the cytoplasm, but considerably decreased in vacuoles and intercellular gaps. Meanwhile, the level of Ca(2+) also increased in chloroplast and nucleus. When the treatment continued, the level of Ca(2+) in chloroplasts and nucleus continued to increase and some cells and chloroplasts finally disintegrated, showing that there is a relationship between the distribution of Ca(2+) and the super-microstructure of cells. Ca(2+) plays a role in the plant drought resistance. The changes of cytosolic Ca(2+) localization in cells treated by ABA, EGTA, Verapamil and TFP were investigated too. The increase of cytosolic calcium induced by ABA was mainly caused by calcium influx. Calmodulin participated in ABA signal transduction, which was indicated by the variation of cytosolic Ca(2+)/CaM concentration change induced by ABA. The above results provided a direct evidence for calcium ion as an important signal at the experimental cellular level.