Allocation of Macronutrients in Roots, Sheaths, and Leaves Determines Salt Tolerance in Rice

Abstract

To determine useful parameters for salt tolerance in rice and selection of salt-tolerant varieties, their macronutrient contents in roots, sheaths, and leaves were evaluated under salt stress condition. A hydroponic experiment was conducted to evaluate 29 rice varieties for salt tolerance. The salt stress treatment included an artificial seawater solution (electrical conductivity of 12 dS·m-1). After a 2-week period of salt stress, standard evaluation scores (SES) of visual injuries for salt stress were assessed. In addition, we measured the contents of N, P, K, Na, Mg, and Ca in roots, sheaths, and leaves. The results showed that differences in macronutrients in the different plant tissues correlated with rice tolerance to the salt stress condition. Under the control treatment, salt-tolerant varieties exhibited low K content in root. Under the salt stress treatment, the salt-tolerant varieties exhibited low SES, high N content in leaves and sheaths, low Na content in leaves and sheaths, low Mg content in leaves and sheaths, and low Ca content in sheaths. The salt-tolerant varieties also exhibited high salt stress treatment/control treatment (ST/CT) ratios for dry matter in sheaths, N content in leaves and sheaths, and K content in sheaths, and low Na/K ratios in leaves and sheaths. Therefore, these parameters might be useful to understand salt tolerance in rice.