大气CO2浓度升高条件下稻稗共生系统中稗草对水稻光合生理的影响

稗草是水稻田的恶性杂草之一，严重影响水稻的生长发育和产量形成。为明确CO2浓度升高条件下稗草和水稻的光合生理响应及其竞争关系变化，以吉粳88为研究对象，利用开放式CO2浓度富集系统（FACE系统）开展模拟试验。试验设置2个CO2浓度，分别为自然大气CO2浓度（400µmol·mol?1）和高CO2浓度（550µmol·mol?1），高CO2浓度环境应用FACE系统进行调控；每种CO2浓度处理中设2种种植方式，分别为清种水稻和水稻与稗草混种，稗草与水稻种植密度比为1:5，在水稻各生育期测定相应的光合生理指标并进行分析。结果表明：CO2浓度升高使水稻每穴穗数显著增加，结实率也有所提高，最终使水稻产量显著提高；稗草与水稻混种使水稻结实率显著降低，水稻千粒重显著增加，最终使水稻产量显著降低；CO2浓度升高和稗草互作使水稻千粒重显著提高，但对产量影响并不显著。CO2浓度升高使水稻干物质量显著提高，稗草使水稻干物质量显著降低；而CO2浓度升高和稗草互作对水稻干物质影响不显著。CO2浓度升高使水稻剑叶净光合速率、胞间CO2浓度及SPAD值显著升高，使水稻剑叶气孔导度和蒸腾速率显著降低，稗草显著降低了水稻剑叶净光合速率、胞间CO2浓度、气孔导度、蒸腾速率、瞬时水分利用效率及SPAD值；CO2浓度和稗草互作使水稻剑叶净光合速率先降低后升高。水稻抽穗后CO2浓度升高对水稻光合作用的影响大于稗草对水稻光合作用的影响。

Impacts of Barnyard Grass on Photosynthesis and Physiology of Rice under Elevated Atmospheric CO2 Concentration

Barnyard grass is one of the vicious weeds in rice field, which affects seriously the growth and development of rice and reduces the yield of rice. In order to clarify the effect of barnyard grass on rice growth and development and yield formation under the condition of elevated atmospheric carbon dioxide (CO2) concentration, the experiment was conducted with the Free-Air CO2 Enrichment system (FACE system), taking rice Jijing 88 as material. The experiment included 4 treatments: atmospheric CO2 concentration (400µmol·mol?1) without barnyard grass, rice planting and barnyard grass together with atmospheric CO2 concentration, elevated CO2 concentration (550µmol·mol?1) without barnyard grass, rice planting and barnyard grass together with elevated CO2 concentration. Physiological indicators were measured and analyzed at the tillering stage, jointing stage, heading stage, and mature stage of rice. The results showed that elevated CO2 concentration increased significantly the number of rice ears per hole and the seed setting rate, and eventually increased the rice yield. Barnyard grass significantly reduced the rice seed setting rate, and reduced rice yield ultimately. Interaction of elevated CO2 concentration and barnyard grass increased significantly thousand-grain weight of rice, yet, the interaction did not affected rice yield significantly. Elevated CO2 concentration increased significantly the dry matter of rice, and barnyard grass reduced significantly the dry matter of rice. However, the interaction of elevated CO2 concentration and the barnyard grass had no significant difference. Elevated CO2 concentration increased significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 of the flag leaf, and the Soil and Plant Analyzer Developrnent (SPAD) value of rice flag leaf. Barnyard grass treatment reduced significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 in the flag leaf, the stomatal conductance, the transpiration rate, the instantaneous water use efficiency, and the SPAD value. The interaction of elevated CO2 concentration and barnyard grass reduced the net photosynthetic rate of rice flag leaves at early stage, and increased it at later stage. In conclusion, Elevated CO2 concentration after heading stage had a greater impact on rice photosynthesis than barnyard grass on rice photosynthesis.