Effects of non-uniform root zone salinity on water use Na+ recirculation and Na+ and H+ flux in cotton

摘要

A new split-root system was established through grafting to study cotton response to non-uniform salinity. Each root half was treated with either uniform (100/100 mM) or non-uniform NaCl concentrations (0/200 and 50/150 mM). In contrast to uniform control, non-uniform salinity treatment improved plant growth and water use, with more water absorbed from the non- and low salinity side. Non-uniform treatments decreased Na⁺ concentrations in leaves. The [Na⁺] in the ‘0’ side roots of the 0/200 treatment was significantly higher than that in either side of the 0/0 control, but greatly decreased when the ‘0’ side phloem was girdled, suggesting that the increased [Na⁺] in the ‘0’ side roots was possibly due to transportation of foliar Na⁺ to roots through phloem. Plants under non-uniform salinity extruded more Na⁺ from the root than those under uniform salinity. Root Na⁺ efflux in the low salinity side was greatly enhanced by the higher salinity side. NaCl-induced Na⁺ efflux and H⁺ influx were inhibited by amiloride and sodium orthovanadate, suggesting that root Na⁺ extrusion was probably due to active Na⁺/H⁺ antiport across the plasma membrane. Improved plant growth under non-uniform salinity was thus attributed to increased water use, reduced leaf Na⁺ concentration, transport of excessive foliar Na⁺ to the low salinity side, and enhanced Na⁺ efflux from the low salinity root.