Relationship between Callus Growth and Mineral Nutrients Uptake in Salt-Stressed Indica Rice Callus

One month old rice calli were exposed to 0, 50, and 100 mol m-3 sodium chloride (NaCl) in the liquid LS basal medium supplemented with 2.5 mg L-1 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.5 mg L-1 kinetin. Callus relative growth rate (RGR; fresh) of both cultivars indicated a progressive decrease; however, callus dry weight increased as the NaCl level increased in the culture medium. Salinity stress increased the callus sodium (Na+), manganese (Mn2+), and magnesium (Mg2+) contents while potassium (K+), calcium (Ca2+), and iron (Fe2+) contents decreased. 'Basmati-385' showed less reduction in callus RGR, K+, and Ca2+ contents and a larger increase in callus dry weight, Na+, Mn2+, and Mg2+ contents as compared to 'Basmati-Karnal'. However, the reverse was true for Fe2+ contents. K+/Na+ and Ca2+/Na+ ratios generally decreased under salt stress. Overall, reduction in callus relative growth rate was found to be inversely correlated with decrease in K+, Ca2+, and Fe2+ uptake and directly correlated with increased Na+ and Mg2+ concentration in callus tissue.