Effects of Root Temperature, Mineral Nutrition, and Salinity on the Growth and Composition of Rice

Abstract

1. Two water-culture experiments were conducted with Caloro rice grown at several constant root temperatures and several levels of nutrition or salinity. In the first experiment, growth of shoots, roots, and grain was decidedly better at a high than at a low cation level. Variations in cationic ratio brought about changes in cation content of shoots and roots. This altered cation content did not significantly affect vegetative growth, but grain yields were significantly greater on isoequivalent (Ca=Mg=K) and high-K solutions than on high-Ca or high-Mg solutions. At a constant root temperature of 18⚬ C., shoot growth was twice that at 30⚬ C., and root growth one and a half times as great; however, grain yield was only three-fourths as much at the lower root temperature. There were no statistically significant interactions between root temperature and cationic concentration or cationic ratio. 2. In the second experiment the nutrient solution which had allowed the most growth (the isoequivalent solution at t...