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 CO₂ and 0.6, 6, 60 or 600μM phosphorus (P) nutrition with other growth conditions of 12-h day (450μmol m^-2 s^-1 PPFD) /12-h night cycle at 28/23°C and about 60% RH. Generally, the growth and dry matter production were promoted by high CO₂ and the effects were enlarged with elevating P level up to 60μM but the highest P (600μM) decreased the CO₂ effects. At the lowest P (0.6μM), the root growth was substantially promoted at the sacrifice of shoot growth. The net assimilation rate (NAR) was largely promoted by high CO₂ but not by P nutrition. The high CO₂ 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 CO₂, probably because of the dilution effect of carbohydrate accumulation. The P use efficiency in dry matter production decreased with increasing P levels but high CO₂ ameliorated the effect of P. It was concluded that the growth of rice plants in poor P conditions would be ameliorated at high CO₂ levels. However, substantial amounts of P should be applied for their full growth.