The Effects Of Elevated CO₂and O₃to Photosynthetic Parameters And Rice Quality Of Shanyou63

Intensification of human activities has led to the atmospheric environment changing at an unprecedented speed, and one significant change is the rapid rise of the concentration of atmospheric carbon dioxide (CO2), which has risen from280ppm in preindustrial times to393ppm at present, and will reach at least550ppm in2050. With the increasing of the concentration of CO2, the most common air pollutants near the ground area, ozone (O3), also increased rapidly. It is predicted that in the next40years, the concentration of the average tropospheric O3in Southeast Asia area will be25ppb higher. Rice is one of the world’s most important food crops. There are many reports about the effects of elevated CO2or O3on rice, however, little is known about the rice response to the interactive effects of CO2and O3. To investigate the effects of elevated CO2and O3to photosynthetic parameters and quality of rice, we conducted a solar-illuminated gas fumigation platform at Yangzhou University, Jiangsu Province. A three-line hybrid India rice Shanyou63was grown at5treatments:outdoor control (Ambient), indoor control (CK), elevated CO2(200ppm above ambient), elevated O3(elevated by60%) and elevated CO2and O3. We measured photosynthetic parameters at the early and late growing season in2012and processing, appearance, cooking/eating and nutritional quality after harvest in2011and2012. The main results are as follows:1. Elevated CO2significantly increased net photosynthetic rate, intercellular CO2concentration and water use efficiency by15%,48%and43%at jointing stage and28%,64%and21%at filling stage, respectively. Elevated O3significantly decreased net photosynthetic rate, stomatal conductance and transpiration rate by32%,69%and32%at jointing stage and88%,79%and71%at filling stage, respectively. Elevated CO2and O3significantly decreased net photosynthetic rate, stomatal conductance and transpiration rate by8%,61%and20%at jointing stage and48%,22%and24%at filling stage, respectively, meanwhile increased intercellular CO2concentration by46%and82%at jointing and filling stages, respectively.2. Elevated CO2showed no effects to processing quality of rice. Elevated O3significantly reduced milled and head rice rate by1-2%. Elevated CO2and O3significantly decreased brown rice rate by1%.3. Elevated CO2significantly increased brown, milled and head rice yield by45%,45%and28%, respectively; elevated O3significantly decreased brown, milled and head rice yield by43%; elevated CO2and O3made slight effects to brown, milled and head rice yield.4. Elevated CO2showed no effects to processing quality of rice. While elevated O3significantly increased chalky grain rate, chalky area and chalkiness by39%,56%and114%, respectively and elevated CO2and O3significantly increased chalky grain rate, chalky area and chalkiness by22%,42%and72%, respectively.5. Elevated CO2significantly increased gel consistency and amylose content by12%and8%, respectively. Elevated O3significantly decreased total starch, amylose, and digestible starch content by3%,15%and3%, respectively, while increased gelatinization temperature by2%. Elevated CO2and O3made slight effects to cooking and eating quality.6. Elevated CO2significantly decreased concentrations of protein, N and PN, ranging from9%to12%. Elevated O3significantly increased concentrations of protein, N and PN, ranging from23%to50%. Elevated CO2and O3significantly increased concentrations of protein, N and PN, ranging from7%to17%. After testing the content of K, Ca, Na, Mg, P, Cu, Fe, Mn, Zn, we found that e levated CO2significantly decreased concentrations of every element, ranging from8%to43%. Elevated O3significantly increased concentrations of K, Mg, P, Cu, Mn, Zn, ranging from16%to53%, but led to the decrease of Ca and Fe by10%and30%, respectively. Elevated CO2and O3significantly increased concentrations of P and Zn by10%and4%, and decreased the concentration of Cu, Fe by23%and39%, respectively.7. Elevated CO2significantly increased peak viscosity, hot paste viscosity, breakdown, cool viscosity and consistency by8%,5%,14%,4%and5%, respectively, and decreased setback by25%. Elevated O3significantly decreased peak viscosity, hot paste viscosity, breakdown, cool viscosity and consistency by18%,13%,29%,9%and6%, respectively, and increased setback and time of peak viscosity by57%and1%. Elevated CO2and O3slightly increased peak viscosity, the hot viscosity and cool viscosity and decreased breakdown and setback.8. Most parameters of processing, appearance quality, elements content and RVA profile characteristics had significant difference between years. The CO2×year interaction had great impact on most parameters of RVA profile characteristics. The O3×year interaction had great impact on appearance, cooking and eating quality, elements content and RVA profile characteristics. The (CO2+O3) X year interaction had great impact on appearance quality and RVA profile characteristics.In summary, elevated CO2enhanced photosynthesis of hybrid rice, while elevated O3inhibitated photosynthesis. Elevated CO2decreased processing, appearance and nutritional quality and increased cooking and eating quality. Elevated O3reduced processing, appearance as well as cooking and eating quality while increased nutritional quality. The results showed that elevated CO2ameliorated the inhibition of photosynthesis, processing, appearance and nutritional quality of rice induced by O3exposure.