CHANGES OF THE LEVEL OF Ca²⁺ IN CELLS OF LO-QUAT LEAFLETS UNDER LOW TEMPERATURE STRESS

The changes of Ca²⁺ localization in cells of loquat( Eriobotrya japonica Lindl.) leaflets under chilling stress were investigated with calcium antimonate precipitate electromicroscopic cytochemical methods.When loquat leaflets grew at the optimum temperature, it was shown that the deposits of calcium antimonate, being the indicator for Ca²⁺ localization, mainly concentrated within the vacuoles and intercellular spaces, and that there was also some Ca²⁺ deposits in plastid, mitochondria, cytoplasm and nucleus.This indicates that under the normal condition, the vacuoles are the main pool of Ca²⁺ in plant cells, and that there is quite an amount of Ca²⁺ in the intercellular spaces.On the contrary, the free Ca²⁺ in cytoplasm and nucleus is very low under the normal condition.When the loquat leaflet was treated at the temperature of 4℃ for 44 hours, the level of Ca²⁺ in cytoplasm and nucleus increased considerably.Under the chilling stress, there are a great amount of Ca²⁺ deposits in vacuolar, chloroplast, plasma membrane and vacuole membrane.The membrane of nucleus in the cold sensible variety had been damaged and some nuclear substance let out.There were only stroma thylakoids in the cells of cold resistant variety, while many basal granules in the cold sensible variety.The membrane of chloroplasts had been damaged.