Cellular Calcium Distribution Modulates the Growth of Callus and Protoplasts of Halophyte Mangrove Plant, Avicennia Alba - an X-ray Microanalysis

摘要

Two cultured cell lines were developed from cotyledons of a halophyte mangrove, Avicennia alba.In the high-Ca callus line, which was sub-cultured in amodified amino acid medium containing 3 mM CaCl2, growth of calluses and their protoplasts were both inhibited by low concentrations of CaCl2 in the culture medium. Removal of Ca2+ from the culture medium stimulated callus growth and the calluses could be sub-cultured without CaCl2 (low-Ca callus line). The intra- (cytoplasmic matrix and vacuole) and extra- (cell wall) cellular concentrations of elements, i.e., [Ca], [K], [Cl], [Na], [Mg], [P] and [S] were investigated using quantitative X-ray microanalysis of cryosections of calluses from bothcell lines. [Ca] was high in the cytoplasmic matrix and cell wall of the high-Ca line. [Ca] was lowered in the low-Calineinall cell compartments, though still detected. Ca-containing electron-dense precipitates were accumulated in the middle lamella of cell walls in resin-embedded sections of the high-Ca line. CaCl2 in the medium stimulated protoplast growth only in the low-Caline. These results suggested that a low cellular [Ca] is needed for protoplasts growth of A. alba. The importance of cellular [Ca] for the growth of halophilic mangrove plant cells was discussed.