Effects Of Elevated Atmospheric CO₂ And Two Cultivation Practices On The Yield And Quality Of Japonica Rice In Cold Region

The increase of global atmospheric carbon dioxide(CO2) concentration has become an indisputable fact, and at present a broad range of research have been devoted to the effect of elevated atmospheric CO2 on Rice yield(Oryza sativa L.). But those research mostly focused on two levels of CO2 concentration(ambient CO2,~390μmol?mol-1 and elevated CO2, ~550μmol?mol-1); Therefore our study use new type of CO2–Temperature Gradient Chamber(CTGC) to research japonica rice(Wuyoudao no.4) yield components and yield responds to five CO2 concentrations(390-600μmol?mol-1) gradient elevated, and related to the water-saving cultivation rice grown at two cultivation treatments: traditional flooding(TF) and non-flooded plastic film mulching(PM). This study results show that:1、Elevated CO2 has no significant effects on Songjing 9 rice yield in two cultivation treatments, but for the factors of yield the results indicated that, elevated CO2 has no effects of the PM rice spikelet number per panicle, degenerated spikelet number, filled spikelet number and filled spikelet percentage, but when CO2 concentration rising to 500μmol?mol stimulate spikelet number per panicle increased 23.5% of TF patterns. This is caused by elevated CO2 the degenerated spikelet number decreased by 36.3%, filled spikelet percentage was increased 3.3%. Noteworthy, on average due to elevated CO2 the degenerated spikelet number of secondary rachis branches decreased by 75.1%, and filled spikelet number increased by 43.2%, moreover that is the main reason for the increase of the TF rice yield. When CO2 concentration rising to 600μmol?mol stimulate 1000-grain weight increased of two cultivation patterns. Although, the factors of yield were improved under elevated CO2, but the number of panicles per square meter in two cultivation treatments all decreased along with respect to the progressive CO2 concentration gradient. So the grain yield of Songjing 9 rice has no significant response for elevated CO2.2、TF Wuyoudao 4 rice yield increased 25% when the CO2 concentration in the range of 450-500μmol·mol-1, but PM Wuyoudao 4 rice yield has no significant response for elevated CO2, except when CO2 concentration rising to 500μmol?mol the yield was decreased 21%. This is due to elevated CO2 increased the TF rice spikelet number per panicle and filled spikelet percentage, but had no effect on PM rice. Noteworthy, on average due to elevated CO2 the degenerated spikelet number of secondary rachis branches decreased by 75%, and filled spikelet number increased by 43%, moreover that is the main reason for the increase of the TF rice yield. When CO2 concentration rising to 550-600μmol?mol stimulate 1000-grain weight increased 8-9% of PM, but no effects in the TF cultivation. Although, in elevated CO2 concentration the number of panicles per square meter under two cultivations all decreased. But the other factors of grain yield has significant increased in elevated CO2, so the grain yield was significant increased.3、CO2 concentration gradient increased decreased the chalky grain rate and chalkiness degree of Songjing 9 of TF cultivation 39.7-50.8% and 48.5-61.4% respectively, however these factors in PM cultivation increased 28.6-77.3% and77.5% respectively. Elevated CO2 has no effects on chalky grain rate and chalkiness degree of TF Wuyoudao 4 rice, but these factors decreased 34.5-80.5% and 53.1-77.1% respectively under the PM cultivation of Wuyoudao 4 rice.4、Elevated CO2 decreased by 9.3-12.0% the protein content of TF Songjing 9 rice, however no effect in PM treatments. Under two cultivation practices along with respect to the progressive CO2 concentration gradient. the protein content of Wuyoudao 4 rice all significant decreased 2.7-3.4% and 3%. The amylose content of Songjing 9 rice of TF cultivation was decreased along with the progressive CO2 concentration gradient, but in PM cultivation the amylose content significant decreased of Songjing 9 rice when CO2 concentration increased 600μmol?mol-1. Under tow cultivations, the amylose content of Wuyoudao 4 all decreased with elevated CO2.5、CO2 concentration gradient increased improved the eating quality of Songjing 9 rice, such as the color, taste, mouthfeel and comprehensive taste value increased by 8.3-17.1%, 5-8.3%, 13-13.7% and 8.3-10.1%, but the head of rice was decreased 7.7%. However, those factors has no effects for elevated CO2 on PM rice. And elevated CO2 has no effects on the color, taste, mouthfeel and comprehensive taste value of Wuyoudao 4 rice under two cultivation practices. But the head of PM Wuyoudao 4 rice was decreased by 5.8%.6、Compare two cultivation of rice quality we found that, the grain quality of PM Songjing 9 rice under elevated CO2 better than TF cultivation. The chalky grain rate and chalkiness degree of Songjing 9 rice under PM cultivation lower 67.9% and 65.6% than TF cultivation, but the brown rice, milled rice, head milled rice rate and protein content higher 2.1%, 10.7%, 65.8% and 7.3% respectively than TF cultivation. For Wuyoudao 4 rice the grain quality in TF cultivation better than PM cultivation under elevated CO2. The chalky grain rate and chalkiness degree of Wuyoudao 4 rice under TF cultivation lower 65.4% and 70.3% than PM cultivation, but the milled rice, head milled rice rate and protein content higher 3%, 45.1% and 2.4% respectively than PM cultivation. Under elevated CO2 the eating quality of TF rice of two cultivars rice all better than PM rice.