Growth, Yield and Photosynthetic Activity of Vigna radiata L. Grown at Different Temperature and Light Levels

抄録

Two varieties of mungbean (Vigna radiata L.), BARImug 2 (M2) and BARImug 3 (M3) were grown under 1) 12-h light at 700 μmol m^-2 s^-1 (HL) at 30°C/12-h darkness at 25°C (HL+LT), 2) 12-h HL at 40°C (HT)/12-h darkness at 25°C (HL+HT) and 3) 12-h light at 200 μmol m^-2 s^-1 (LL) at HT/12-h darkness at 25°C (LL+HT), and their growth, yield and photosynthetic activities were analyzed. The plants grown under LL+HT were the tallest followed by those grown under HL+HT and HL+LT, in this order. The leaf area was the largest under HL+LT followed by LL+HT and HL+HT. In general, the plants grown under HT had lower biomass compared with those grown at LT. Grain yield was zero (no pod setting) under HL+HT in both varieties, but that under LL+HT was 30-40% of that under HL+LT. M3 produced higher grain yield as well as higher biomass than M2 under both HL+LT and LL+HT. The yield reduction under LL+HT was primarily due to the substantial reduction in the number of pods per plant as well as number of seeds per pod. HT decreased the photosynthetic CO₂ assimilation rate (Pn), and the plant under HL+HT had lower Pn than those under HL+LT. The heat acclimation of photosynthetic apparatus was considered to proceed more easily under HL than under LL, because the photochemical efficiency of PSII (Fv/Fm) and quantum yield of PSII electron transport (FΔ/F’m) after heat shock at 50°C were greatly higher in the plants grown under HL+HT than those under HL+LT. It was concluded that HL at HT inhibited pod setting but accelerated the heat acclimation of photosynthetic apparatus of mungbean.