Studies on the nutrition of the rice plant with reference to Helminthosporium leaf spot (Preliminary report) : VI Nutrients absorption as affected by the light intensity

We have made a study on the influence of shading treatment in midsummer season upon the nutrient absorption of the rice plant growing in nutrient solution with and without H2S. Result of the experiment is as follows : - (1) The shading treatment decreased the absorption of CaO, NH3-N, MnO and H2O, while it increased the absorption of K2O and SiO2. Irrespective of the amount of H2S given the retardation of nutrient-absorption due to shading treatment was in the order K2O < SiO2 < P2O5 < MnO < NH3-N < CaO. (2) Irrespective of the light intensity, hydrogen sulphide reduced the uptake of nutrients in the order K2O < SiO2 > P2O5 > NH3-N > MnO > CaO and such a retardation in the uptake of nutrients due to hydrogen sulphide was less marked under shaded condition. (3) These results seem to suggest that light affects unfavorably the normal aerobic metabolism of the root, at least under high temperature and strong light intensity of midsummer, and cause the reduction in the uptake of ions possessing high values of hydration.