Effects of Atmospheric Partial Pressure of CO2 and Phosphorus Nutrition on Growth of Young Rice Plants.

Abstract

Young rice plants were solution-cultured in artificially illuminated growth cabinets under combinations of 35 (ambient) or 70 (high) Pa atmospheric CO-2 and 0.6, 6, 60 or 600 mu-M phosphorus (P) nutrition with other growth conditions of 12-h day (450 mu-mol m-2 s-1 PPFD)/12-h night cycle at 28/23 degree C and about 60% RH. Generally, the growth and dry matter production were promoted by high CO-2 and the effects were enlarged with elevating P level up to 60 mu-M but the highest P (600 mu-M) decreased the CO-2 effects. At the lowest P (0.6 mu-M), the root growth was substantially promoted at the sacrifice of shoot growth. The net assimilation rate (NAR) was largely promoted by high CO-2 but not by P nutrition. The high CO-2 decreased the leaf weight ratio (LWR), which indicated the relative promotion of dry matter partitioning to organs other than leaves. The mineral nutrient (P, K, Ca, Mg) content was also decreased by high CO-2, probably because of the dilution effect of carbohydrate accumulation. The P use efficiency in dry matter production decreased with increasing P levels but high CO-2 ameliorated the effect of P. It was concluded that the growth of rice plants in poor P conditions would be ameliorated at high CO-2 levels. However, substantial amounts of P should be applied for their full growth.