Potassium and sodium contents of shoot and laminae of rice cultivars and their sodicity tolerance

Abstract

A greenhouse study with 4 to 5 rice (Oryza sativa L.) cultivars was conducted to evaluate the potassium (K) and sodium (Na) contents of shoot and lamina as a basis for their differential sodicity tolerance during two Kharif seasons in Karnal, India. Cutlivar response to sodicity was significant with an increase in stress. Grain yield of each cultivar was much more adversely affected compared to that of shoot dry weight. The concentration of Na in the shoot as well as the lamina increased with increasing sodicity levels, whereas the reverse was true for ? although the total of monovalent cations (Na+K) remained less compared to that of the control (pH 8.1). A well regulated distribution of Na in various laminae was observed. The first lamina (fully expanded from top) had the lowest while the third lamina had the highest Na concentration irrespective of the cultivar, sodicity level, or plant age. However, such uniform patterns were not observed for K. Behavior of cultivar in terms of Na accumulation did not differ whether assessed on the basis of whole shoot or any of the laminae. However, the absolute value of Na was inadequate to explain the differential tolerance among the cultivars. Cultivar IR 4630–22–2‐5–1‐2, a relatively poor performer, was able to tolerate much higher Na concentrations in its laminae compared to that of cultivar CSR 1, the most tolerant genotype to sodicity. Firing of the older laminae seems to be due to a loss of control on the isolation of Na from metabolically active sites as their absolute values of Na were not distinct from that of the relatively younger.