水稲生育相, 特にその栄養生理的特性の地域性について(第3報) : 本田に於ける水稲の生育に伴う3要素含有率の消長

抄録

In the first report, the two types of growth processes of rice plants were distinguished morphologically. The one is the cool area type and the other is the warm area type. This report describes the nutrio-physiological characterization of these two distinguished types. The same samples which were used in the first were used also in the present experiment. Following are description of the nutrio-physiological characteristics of growth processes studied. l) The cool area type : The temperature at transplanting is very low and unfavourable for revival from damage by transplanting. The level of three manurial elements of seedlings at the time of transplanting is high. This physiological condition of seedlings is furnished by managment of nursery and is favourable to compensate for the handicap by climatic condition. After transplanting, absorption of mineral elements by rice plant is severely interrupted for some time because of the low temperature of paddy soil. After revival, nitrogen absorption becomes more rapid and rice plant begins to tiller actively. When temperature rises, ear-primordia are initiated by the temperature-effect. At this time, phosphorus in soil starts to increase in solubility in connection with the condition of iron in soil, so rice begins to absorb phophorus actively and absorption of the other elements is also facilitated by the active absorption of phosphorus. Thus rice plants continue to tiller after ear-initiation until nitrogen level in leaf-and-stem drops below 1.6%. Even at the time of flowering, nitrogen and phosphorus leves in leaf-and-stem are high. The most part of these elements in leaf-and-stem at flowering stage enters into constituents of ear. 2) The warm area type : The temperature at the time of transplanting is high and phosphorus in soil at that time is more available than in the of cool area. These conditions are favourable for revival from damage by transplanting and for acceleration of elements by plants. So, even if the regenerating power of seedlings is very weak, they revive soon and the level of elements in rice plant rises temporarily after transplanting. But after that period, the power of carbon-assimilation of rice plant becomes compratiuely higher than that of mineral accumulation. So, the level of elements of rice plant drops. In this way, nitrogen level drops below 1.6% at rather an early stage of growth and the number of tillers of rice plant decreases after this period. Ear-Primordia are initiated about two weeks later than the time of maximum tiller number stage through the photo-periodic effect. Nitrogen level at the ear-initiation stage is about 1% and this low nitrogen level seems to be unsuitable for the formation of new organs. At the time of flowering, both nitrogen and phosphorus level in leaf-and-stem are low and only a small amount of these elements is found in leaf-and-stem as storage matter. Elements which enter into the ear as the constituents are chiefly absorbed after flowering. So, the stoppage of the nutrient supply after flowering stage results in serious yield depression in warm area.