Influence of Mannitol on Absorption and Retention of Rubidium by Excised Corn Roots

Abstract

Excised root segments of corn were subjected to osmotic stress by immersion in solutions of mannitol before, during, or after a period of Rb absorption. Both the time course of uptake (or loss) and selectivity of uptake were studied. Stress before or during the absorption period reduced Rb absorption to 20 % or less of that of controls, whereas it had no detectable influence on the constancy and selectivity of uptake. Stress imposed following a period of Rb accumulation caused root segments to lose only slightly more Rb than controls during the first 30 min, after which rates of change were insignificant in both. Segments stressed after the Rbabsorption period retained from 70-90 % as much Rb as did the controls, even after two hours. The comparatively great quantitative difference between effect of stress on uptake and its effect on loss is interpreted to mean that the mechanism of stress-induced reduction of ion absorption cannot be adequately explained on the sole basis of increased efflux of ions.

42K analysis of sodium‐induced potassium efflux in barley: mechanism and relevance to salt tolerance

“…6c) also strongly suggests that osmotic stresses are at least partially responsible for the observed enhancements of K + efflux. While this finding contradicts that of Shabala et al (2006), who, it should be noted, used mannitol at concentrations hypo-osmotic to comparative Na + treatments, it is in agreement with many other studies showing increased K + efflux, or decreased K + retention, upon application of nonionic osmolytes (Sutcliffe, 1954;Greenway et al, 1968;Dessimoni Pinto & Flowers, 1970;Smith et al, 1973;Nassery, 1975Nassery, , 1979Cramer et al, 1985). However, in the present study, mannitol was not as effective as NaCl in sustaining the stimulated K + efflux (as also seen by Nassery, 1975Nassery, , 1979, indicating that there may be both osmotic and ionic components to the stimulatory stress, just as there are both osmotic and ionic components responsible for salt injury to plants (Munns & Tester, 2008).…”

Efflux of Potassium from Wheat Roots Induced by Changes in the Water Potential of the Root Medium

“…Although Miller et al (1971) reported that water stress had a marked effect on membrane permeability and ion transport in isolated corn mitochondria, the effect of water stress on efftux of Rb from excised root segments of corn were insignificant according to Smith et al (1973), who concluded that stress-induced reduction of ion uptake could not be explained by increased efflux. However, based on experiments with excised barley and tomato roots Greenway et '-•I.…”

Rapid Effects on Ion and Water Uptake Induced by Changes of Water Potential in Young Wheat Plants

“…In recent years, a large number of data on water stress effects on various physiological processes in plant tissue have accumulated. Effects on metabolism-linked ion transport have been reported (Dove 1969, Amar and Reinhold 1973, Smith et al 1973 as well as effects on passive ion efflux (Greenway et al 1968, Resnik andFlowers 1971). Submicroscopic cellular disturbances induced by water stress were found by Nir et al (1970) in the nucleus, and by Miller et al (1971) in the mitochondria.…”