Studies on Photosyntthesis in Rice Plant : XII. The effect of three major nutrient element supply upon the photosynthetic activity of rice leaves

The effect of the three major nutrient element supply upon the photosynthetic activity of rice leaves was studied by water culture experiment. From four series of experiments carried out by the authors over three years at various growing stages of the plant, the following conclusions were drawn : 1) Nitrogen supply most often gives limiting influences upon the photosynthetic activity of rice leaves within comparatively a wide range of its supply or its content in the leaves. If the other elements, however, are too short in their supply, they may become limiting to photosynthesis instead of nitrogen. 2) Phosphorus, on the other hand, may become limiting only when nitrogen supply is abundant, and potassium may become limiting only when both nitrogen and phosphorus are amply supplied. 3) When supplies of the three major elements are higher than their normal levels, the photo-synthetic activity of rice leaves can not be varied remarkably, at least in the earlier half of their growing stage, how the mutual ratios among the three may be changed