Growth Responses of Rice Plant to Environmental Conditions : II. The effects of air-temperature on the organic and mineral composition of the plant parts

Abstract

The dried materials obtained 3 times during the temperature treatments as described in the previous report (I) were analyzed for total-sugar, crude starch, soluble and protein nitrogen, and mineral elements. The results are summarized as follows. 1) Total nitrogen concentration declined with the development of growth, but that of soluble-N was almost constant. Both soluble-and protein-N concentrations and soluble-N to protein-N ratio increased as temperature decreased. The ratios were highest at leaf-sheath (including stem), lowest at leaf-blade. Norin- 17 showed the higher values in this ratio than IR-8 at leaf-sheath and roots. 2) Total sugar concentrations were highest at leaf-blade and lowest at roots, but crude starch concentrations were highest at leaf-sheath, both being increased with the decrease of temperature. IR-8 showed a higher total sugar/crude starch ratio than Norin-17, especially at leaf-blade. 3) TAC/N ratios of the shoot were higher in Norin-17 than in IR-8, becoming higher with the development of growth and with the decrease of temperature in both varieties. The leaf-blade at higher temperatures contained much water, indicating a higher photosynthesis. IR-8 leaf contained more water than Norin-17. 4) The concentrations of mineral elements were variously influenced by temperature. There was a tendency that the cations concentrations decreased with the decrease of temperature, while those of anions were a little affected. Total cations/total anions, K/N, Mn/Fe, Mg/Ca, all these ratios decreased with the decrease of temperature. No definite ionic antagonism was found between K and Mg or Ca. The concentrations of N, Ca + Mg were higher at leaf-blade than at leaf-sheath, while those of K and Si were higher at leaf-sheath. 5) At higher temperatures than the optimum, the check of nitrogen absorption was more severe than that of growth, while at lower temperatures, the check of cations absorption was more severe than that of growth. It is considered that the decrease of growth at higher or lower temperatures than the optimum are connected with the check of nitrogen absorption with a less TAC content at the former, and with the check of cations absorption with a high ratio of soluble-N/protein-N and an increased TAC content in the latter, respectively. 6) The better growth of IR-8 seems to be caused by the higher ability to utilize the assimilated materials for growth than that of Norin-17.