酸素濃度が作物の光合成および生育におよぼす影響 : 第1報 数種の生育温度下での小麦と水稲の生育におよぼす酸素濃度の影響

抄録

The present study was conducted to clarify the effects of oxygen concentration under various leaf temperatures on the growth of wheat and rice plants (C₃-plants). Seedlings of both species were growth for 7 days in specially devised growth chamber equiped with water culture facilities, under 2.5% O₂, 0.03% CO₂ and 21% O₂, 0.03% CO₂, and at light intensity 45 Klx (at 20. 25 and 30°C leaf temperature) or 25 Klx (at 5 and 10°C) under a regime of 12hr light and 12hr darkness. The growth paramenters of the plants were investigated at the start and the end of each experiment. The results obtained are summarized as follows: 1. The dry matter production (ΔW_T and RGR) was enhanced in both species under overall leaf temperatures, and plant height and leaf emergence were somewhat inhibited except at 30°C in wheat and 20°C in rice plant with low oxygen ooncentration. 2. NAR of both species enlarged extremely at low oxygen concentration under overall leaf temperatures. According to these results, it can be deduced that acceleration of the apparent photosynthetic rate at low oxygen concentration, due to suppression of the photorespiration et al., persists for a long time. 3. NAR and RGR were enhanced under low leaf temperature (5 and 10°C) at low oxygen concentration, therefore these results suggest that the function of photorespiratory mechanism still may continue under low leaf temperature. 4. It has been shown that the apparent photosynthetic rate increases at low oxygen concentration with leaf temperature increases, and it reaches maximum rate at 30∼35°C. However, RGR of both species at low oxygen concentration in this experiment was greatest at 20°C and it decreased with falling or rising temperature. It is considered that at low oxygen concentration the optimum temperature for the apparent photosynthetic rate as momentary value does not fit the maximum growth of plants. On the other hand, difference between RGR at low oxygen concentration and RGR at normal air was greater under higher temperature, hence it can be explained that the effect of suppression of the photrespiration et al., on the dry matter production is greater under higher temperature. 5. RLGR was reduced under low oxygen concentration, and subsequently decreasing of LAR came out. In spite of decrease of LAR, RGR was increased through greater increase of NAR under low oxygen concentration. 6. The surplus dry matter in plants under low oxygen concentration (ΔW at 2.5%O₂-ΔW at 21% O₂) was allotted to leaf blades and roots in wheat, and leaf sheaths+stems and roots in rice plant, respectively. It may be considered that above difference was based on the characteristics of species.