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

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Abstract
Excised roots obtained from maize plants, previously treated for 24 h with different solutes (K2SO4, Na2SO4, or mannitol) at decreasing osmotic potential values, showed clearly the persistence of osmo-saline shock in their chloride transport and in some metabolic processes. In particular, vacuolar accumulation of chloride was much reduced when the osmotic potential in pretreatment had 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 accumulation in the vacuole and protein synthesis. By contrast, accumulation of chloride in the cytoplasm was only slightly modified or even stimulated. Chloride influx was affected less by osmotic pretreatment than accumulation, except in the case of very low osmotic potentials where influx was depressed. Chloride efflux was slightly enhanced by osmo-saline shocks and the fluxes at the tonoplast were less affected in comparison with those at the plasmalemma. Malate accumulation was stimulated by shock, but this effect was not persistent, so that a correlation with the effects on accumulation and fluxes was not possible. Oxygen uptake was affected only slightly except that at osmotic potential values of −750 kPa, perhaps because of a lowered viability of the roots subjected to very low osmotic potential for 24 h.