Chloride and sulphur concentrations in chloroplasts of spinach.

Van Steveninck, Reinhard F. M.; Fernando, Denise R.; Anderson, Christopher A.; Edwards, Linton B.; Van Steveninck, Margaret E.

Chloride concentrations within individual chloroplasts, the adjacent cytoplasm and nearby vacuoles of spinach mesophyll cells (Spinacea oleracea L. cv. Hybrid 102) were determined by means of electron probe X‐ray microanalysis in the cleavage plane of quench frozen tissue, which was maintained at liquid nitrogen temperatures. The accuracy of quantitative data obtained with this technique is greatly improved by the adoption of a peak to background ratio method and use of carbon slurry standards, which mimic the quench frozen tissue and its X‐ray fluorescence. Chloroplasts were incapable of maintaining relatively high levels of Cl− under conditions of low Cl− availability (zero Cl− or 20 μM Cl− in nutrient solution), and under conditions of Cl− stress (100 or 200 mM Cl−) chloroplasts had only a limited capacity to maintain a Cl− concentration at a level below that of the cytoplasm and vacuole. However, under conditions of Cl− stress the concentration of Cl− in cytoplasm immediately adjacent to chloroplasts was substantially higher than in the chloroplasts or more distant cytoplasm. Thus, Cl− levels in chloroplasts are apparently not as tightly regulated as was suggested by estimates of Cl− concentration based on aqueous isolation of chloroplasts. Levels of S in chloroplasts were relatively high (equivalent to 40–60 mM SO42− in S standards) and constant for all treatments, with the possible exception of lower S levels in chloroplasts of leaves approaching premature senescence as a result of salt stress. It is implied that the stability of the S‐content results largely from its presence in macromolecular components of chloroplasts (sulfolipids and proteins).

SPINACH; CHLOROPLASTS; CHLORIDES; SULFUR; ELECTRON probe microanalysis; NITROGEN

Physiologia Plantarum, 1988, Vol 74, Issue 4, p651

0031-9317

Academic Journal

10.1111/j.1399-3054.1988.tb02031.x