Growth and physiological responses of plants to osmotic and sodium stress
2014
Kaburagi, E. (Tottori University, Tottori (Japan). United Graduate School of Agricultural Sciences) | Fujiyama, H.
Salinity mainly inhibits water uptake by plants owing to osmotic stress. Sodicity causes nutritional disorders owing to Na toxicity and high pH. Although the characteristics of salinity and sodicity differ, it can seem that the tolerance of plants to both stresses should be the same. Barley (Hordeum vulgare) is classified as tolerant to salinity and sodicity, and beans (Phaseolus vulgaris) are classified as sensitive to both. However, alfalfa (Medicago saliva) is classified as sensitive to salinity and tolerant to sodicity. The purpose of this study was to elucidate their growth responses to high osmotic and sodic stress conditions and to reveal which factors are responsible for tolerance. Polyethylene glycol solution was used to simulate osmotic aspect of salinity and analyzed the water status of plants by water content and water uptake. We mixed soil with high Na and high pH to create sodic conditions and we determined the ionic concentrations of plants. Under high osmotic strength, barley maintained a high water content and high water uptake, and its growth was not reduced. In contrast, alfalfa and beans showed decreased water content and water uptake. Sodicity did not affect the growth of alfalfa, which was able to maintain lower Na and higher Fe accumulation. In contrast, it increased Na and decreased Fe in barley and beans, and decreased their growth. We conclude that differential physiological responses of plants to high osmotic stress and sodicity clearly explain their tolerance to these stresses.
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