Persistence of Modifications Induced by Osmo-saline Shocks on Chloride Transport and Some Related Metabolic Processes in Roots of Maize Plants

Excised roots obtained from maize plants, previously treatedfor 24 h with different solutes (K₂SO₄, Na₂SO₄, or mannitol)at decreasing osmotic potential values, showed clearly the persistenceof osmo-saline shock in their chloride transport and in somemetabolic processes. In particular, vacuolar accumulation ofchloride was much reduced when the osmotic potential in pretreatmenthad been low; this effect was greater with solutions of electrolytes.Protein synthesis and ¹⁴C]leucine uptake were also reduced;thus there appeared to be a correlation between chloride accumulationin the vacuole and protein synthesis. By contrast, accumulationof chloride in the cytoplasm was only slightly modified or evenstimulated. Chloride influx was affected less by osmotic pretreatmentthan accumulation, except in the case of very low osmotic potentialswhere influx was depressed. Chloride efflux was slightly enhancedby osmo-saline shocks and the fluxes at the tonoplast were lessaffected in comparison with those at the plasmalemma. Malateaccumulation was stimulated by shock, but this effect was notpersistent, so that a correlation with the effects on accumulationand fluxes was not possible. Oxygen uptake was affected onlyslightly except that at osmotic potential values of –750kPa, perhaps because of a lowered viability of the roots subjectedto very low osmotic potential for 24 h.