| Atmospheric CO2 concentration has risen from less than 280 μmol mol-1 in 1800 to current 400 μmol mol-1, and will presumably reach 550 μmol mol-1 in 2050. Hybrid rice with high yield potential and strong resistance traits plays an irreplaceable role to solve Chinese food safety problem. A small amount of research has shown that, the response of hybrid rice to high CO2 concentration may be greater than the conventional rice. But does this high response have the universal for the current super-high-yield hybrid combination in rice production? What is its physiological mechanism? It is still not clear. In order to systematically investigate the effects of high CO2 concentration on growth stage, height, photosynthetic parameters, dry matter production and distribution, grain yield and its components and elements uptake of hybrid rice, a Free Air ozone Concentration Enrichment (FACE) experiment was conducted. Indica-japonica hybrid rice Yongyou2640 and Hybrid-indica rice Y-Liangyou900 (Super rice) whose production had broken a record were grown at two CO2 concentration levels:ambient CO2 concentration and high CO2 concentration (Ambient+200 μmol·mol-1). The main results showed as follows:1. Compared to the control, high CO2 concentration significantly or very significantly shortened the heading stage and maturity stage by 1.5 and 2.5 d respectively. High CO2 concentration significantly increased plant height at different stage except the early growth stage, and two rice cultivars showed the same trend.2. High CO2 concentration significantly increased leaf net photosynthetic rate at jointing stage, heading stage,24 d after heading stage and 42 d after heading stage, but the increase range varied with different cultivars:increased by 50%,40%,49%, and 26% of Yongyou2640, respectively, but increased by 28%,31%,21% and 2% of Y-Liangyou900, respectively. High CO2 concentration significantly decreased stomatal conductance and transpiration rate at different stage except the early growth stage, and the decline range of Y-Liangyou900 were bigger than Yongyou2640. Conversely, high CO2 concentration significantly increased water use efficiency, and the increase range of Yongyou2640 was slightly bigger than Y-Liangyou900.3. When averaged across these two cultivars, high CO2 concentration significantly increased above-ground biomass by 12%,11%,26% and 17% at tillering, jointing, heading and maturity stage, respectively. When comparing with the different growth period, the stage of the biggest increase range was mid-growth period. High CO2 concentration significantly decreased the ratio of dry matter in leaves to that in above ground at different growth stage, and significantly increased the ratio of dry matter in panicles to that in above ground at heading and maturity stage, but the responses of the ratio of stems varied with different growth stage. The increase range of the ratio of Yongyou2640 panicles was greater than that of Y-Liangyou900 under high CO2 concentration.4. High CO2 concentration increased grain yield of two cultivars by an average of 20%, Yongyou2640 and Y-Liangyou900 significantly increased by 28% and 12%, respectively. Yield increase under high CO2 concentration was mainly caused by panicles (+10%), spikelets per panicle (+6%) and total spikelet numbers (+17%), while no significant change was observed in grain-filling ability. There were more than 0.1 significant interactions between CO2 and cultivars for rice yield, panicles, spikelets per panicle and total spikelet numbers.5. Compared to the control, high CO2 concentration significantly or very significantly decreased N, P and K content of above ground by 7.3%-17.0%,4.6%-8.5% and 4.4%-7.1% at tillering, jointing, heading and maturity stage, respectively. High CO2 concentration had no significant effect on N content at different rice growth stage, while P and K content of above ground at different growth period showed a significant increase trend. High CO2 concentration decreased the ratio of N, P and K uptake in leaves that in above ground at different stage, while the increase was observed in stems and panicles, and most cases reached more than 0.1 significant level. High CO2 concentration significantly increased production efficiency of N, P and K uptake at different growth stage and production efficiency of grain at productive phase. There was barely interaction between CO2 and cultivars for above-mentioned parameters.6. The above results indicated that, the effect of high atmospheric CO2 concentration on final yield of Yongyou2640 was obvious greater than that of Y-Liangyou900, and this might be caused by the greater response of sink capicity and without apparent photosynthetic adaptation during the late growth stage of this cultivar. |
PDF Full Text Request