增施磷肥提高弱光环境中夏大豆叶片光合能力及产量

为研究增施磷肥对弱光环境中夏大豆光合能力的调控作用,本研究以齐黄34为供试品种,设置全生育期正常光照(L1)、花后弱光(L2) 2个光照处理,不施磷肥(P0)、常规施磷(P1)、增施磷肥(P2) 3个磷肥处理,通过测定叶片气体交换和叶绿素荧光,系统分析了花后叶片光合能力和产量要素的变化。2年结果表明,花后弱光处理后大豆产量显著降低,平均产量较正常光照组降低61.4%。正常光照环境中,P2比P0和P1处理的2年平均产量分别高8.4%和3.2%,而弱光环境中,P2较P0、P1处理分别增产21.7%与12.2%,表明在弱光环境下增施磷肥增产效果更明显。弱光处理后大豆叶片叶面积、比叶面积和叶绿素a、叶绿素b含量显著增加,增施磷肥进一步扩大其增幅,同时叶片净光合速率与气孔导度明显降低,胞间CO2浓度变化趋势与之相反,证明弱光处理后同化能力的降低不是由于气孔限制。增施磷肥会提高光合速率和气孔导度,在弱光条件下效果更显著。增施磷肥会显著降低叶片叶绿素荧光诱导曲线中的J点和K点相对荧光,提高叶片光系统II电子传递性能,在弱光环境下作用比正常照光下更明显。弱光环境下增施磷肥可提升叶片光合电子传递活性,缓解弱光下叶片光合速率降低,提高大豆植株干物质积累,进而提高产量。

Increasing phosphate fertilizer application to improve photosynthetic capacity and yield of summer soybean in weak light environment

In order to study the effect of phosphate fertilizer application on the photosynthetic characteristics of summer soybean in weak light environment, two light treatments normal light (L1) and weak light (L2)] with three phosphate fertilizer treatments including non-phosphate fertilizer application (P0), conventional phosphate fertilizer application (P1), and excessive-phosphate fertilizer application (P2) in each light treatment were set up to measure the gas exchange, chlorophyll a fluorescence differences of photosynthetic performance as well as the yield and its components in Qihuang 34. The yield reduced significantly in weak light treatment, with an average of 61.4% in two years lower than that under the normal light. The 2-year average yield of P2 was 8.4% and 3.2% higher than that of P0 and P1 respectively under the normal light, but 21.7% and 12.2% higher than P0 and P1 in weak light treatment respectively, indicating the effect of excessive-phosphate fertilizer on yield was more pronounced under weak light. The weak light environment significantly increased the leaf area, specific leaf area, chlorophyll a and chlorophyll b contents, which was enhanced by increasing phosphate fertilizer application. The net photosynthetic rate and stomatal conductance of the leaf decreased significantly in the weak light environment, while the intercellular CO₂ concentration increased, indicating the reduction of carbon assimilation in weak light environment was not limited by stomata. Increasing the application of phosphate fertilizer increased photosynthetic rate and stomatal conductance, which was more obvious under weak light. Excessive-phosphate fertilizer application reduced the relative fluorescence at the K and J points of the OJIP curve, and improved the electron transfer performance of photosystem II, was more significant which in weak light than in normal light environment. Therefore, the increase of photosynthetic electron transport activity effectively alleviates the decrease of leaf photosynthetic rate under weak light treatment, which may be the reason for the significant increase of dry matter accumulation and yield by applying more phosphate fertilizer in weak light environment.