高CO2浓度和遮荫对小麦叶片光能利用特性及产量构成因子的影响

CO2和光能是植物光合作用的动力和底物,它们的变化必然引起植物光合特性和生长的变化。研究大气CO2浓度和光强变化对植物光合生理的影响,有利于认识作物对全球生态变化的生理响应机制。试验以高大气CO2浓度和遮荫为处理手段,通过测定小麦(Triticum aestivum)旗叶的光合气体交换参数、光强光合速率响应曲线和产量构成因子,分析光强光能利用效率之间的关系,研究高大气CO2浓度(760μmol.mol 1)和遮荫对小麦叶片光合特性及产量构成因子的影响。结果表明,高大气CO2浓度下,小麦叶片的净光合速率(Pn)增加;同时最大净光合速率(Pnmax)、光饱和点(LSP)、光补偿点(LCP)显著升高;遮荫处理使小麦叶片的Pnmax、LSP、LCP降低。正常光照下大气CO2浓度升高使小麦叶片呼吸速率(Rd)显著下降,遮荫后大气CO2浓度升高对Rd无显著影响。大气CO2浓度升高能显著提高小麦叶片表观量子效率(AQY),而遮荫对AQY的影响因大气CO2浓度而异,高大气CO2浓度下遮荫使AQY显著提高,正常大气CO2浓度下遮荫则使AQY明显下降。高大气CO2浓度下遮荫使小麦株高、穗长增加,而穗粒数、单株穗粒重、千粒重减小。受光合特性的变化和光强限制,高大气CO2浓度下遮荫使小麦叶片呼吸增强,导致Pn下降,不利于干物质积累和籽粒产量的形成。

Effects of elevated atmospheric CO2 concentration and shading onleaf light utilization and yield of wheat

CO2 and light energy are dynamic substrates of plant photosynthesis.Changes in CO2 concentration and light energy intensity lead to corresponding changes in the characteristics of plant photosynthesis and growth.It was therefore critical to study the effect of atmospheric CO2 concentration and light intensity on plant photosynthesis which could foster further understanding of the response of terrestrial ecosystem to global climate change.This study analyzed the elevated atmospheric CO2 concentration(760 μmol?mol?1) and shading effects on wheat light utilization and yield.In the study,CO2 concentrations and light intensity were set up and measures were taken on photosynthetic gas exchange parameters,light-photosynthetic response curves and yield.The relationship between light intensity and light use efficiency was analyzed and then elevated atmospheric CO2 concentration(760 μmol?mol?1) and shading effects on wheat photosynthesis and yield determined.Result showed that compared with normal CO2 concentration,net photosynthetic rate(Pn),maximum net photosynthetic rate(Pnmax),light saturation point(LSP) and light compensation point(LCP) of wheat leaves increased significantly under elevated atmospheric CO2 concentration.However,under shading conditions,Pnmax,LSP and LCP decreased.Under normal and elevated atmospheric CO2 concentrations,dark respiration rate(Rd) of wheat leaves decreased significantly.However,shading and elevated atmospheric CO2 concentration had no significant effect on Rd.Apparent quantum yield(AQY) of wheat leaves increased significantly with increasing atmospheric CO2 concentration.Conversely,the effect of shading on AQY changed with changes in atmospheric CO2 concentration.While shading significantly increased AQY under elevated atmospheric CO2 concentration,it significantly decreased AQY under normal CO2 concentration.While plant height and spike length increased significantly under elevated atmospheric CO2 concentration and shading,grain number,grain weight per spike and 1000-grain weight decreased significantly.Because of changes in photosynthetic characteristics and limitations in light intensity,wheat leaf respiration increased under elevated atmospheric CO2 concentration and shading conditions.This resulted in the decline of Pn,which limited dry mass accumulation and grain yield formation.