An X-ray microanalysis study of the salt glands and intracellular calcium crystals of Tamarix
Storey, R. | Thomson, W.W.
X-ray microprobe analyses of the secreted salts from glands of 20 Tamarix aphylla (L.) Karst trees growing in alluvial soils in the north western district of Victoria, Australia, show that the glands secrete a variety of elements including calcium, magnesium and sulphur. However, sodium, potassium and chloride, common ions reported to be secreted predominantly in other studies, are present in relatively low amounts in the secreted salts. Calcium, the major cationic element in the secretory product of the gland, was not detected in the symplasm of the secretory and collecting cells or in the vacuoles of the collecting cells. Some evidence indicates that silicon may be secreted by the glands but further corroboratory data are required. Our results support previous suggestions that the glands of Tamarix have a low level of selectivity. Large, spherical aggregates of calcium crystals were observed in the vacuoles of the mesophyll cells and quantitative X-ray microanalysis suggested that the chemical composition of the crystalline aggregates was CaSO4.2H2O. The predominant elements in the vacuolar sap were magnesium and sulphur, probably present as MgSO4, whereas the major elements in the cytoplasm were potassium, sulphur and phosphorus. In Tamarix aphylla the calcium content of the leaf appears to be regulated by both the secretion of calcium salts from the leaf and by intracellular calcification in mesophyll cells.
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