缺磷限制带状复合种植大豆光合作用对光照诱导的响应

Phosphorus deficiency limits photosynthetic induction response to light in soybeans under strip compound planting systems

[目的]磷参与电子传递、光合磷酸化和卡尔文循环等光合作用过程,缺磷会导致作物光合效率下降和产量损失。针对大豆[Glycinemax(L.)Merr.]和玉米(Zea mays L.)带状复合种植时低位作物大豆因波动光环境导致的产量受限问题,探究磷素营养对光照诱导过程中大豆光合作用的影响,为改善大豆光合效率和挖掘大豆生产潜力提供理论依据。[方法]大豆玉米带状复合种植田间试验在四川农业大学进行,设置大豆不施磷(-P)和正常施磷(CK)两个处理。于大豆分枝期,分别在稳态饱和光及光照诱导条件下,测定大豆叶片气体交换参数,包括净光合速率(A)、气孔导度(g_(s))、胞间CO^(2)浓度(C_(i))、蒸腾速率(T_(r))、电子传递速率(J)等,并计算气孔和生化等光合限制因子比例。气体交换参数测定完成后的叶片样品用于测定全磷、无机磷和叶绿素含量。[结果]与CK处理相比,-P处理显著抑制了大豆的生长,籽粒产量和成熟期植株干重分别降低了24.5%和23.9%。缺磷显著降低了分枝期大豆叶片的全磷和无机磷含量,但并未影响叶绿素a、叶绿素b以及类胡萝卜素等光合色素含量。稳态饱和光照下,缺磷导致大豆叶片的A和Tr分别下降了30.9%和39.5%,而对gs无显著影响,使得Ci显著增加;缺磷导致大豆叶片的气孔限制值下降了16.7%,即非气孔因素是引起稳态饱和光照下A下降的主导因素。由低光向高光过渡期间,施磷处理大豆叶片A和gs的诱导速率都显著快于不施磷处理;而J的诱导速率在两个处理之间无显著差异。光合限制分析结果显示,光照诱导过程中施磷处理累计气孔限制和生化限制之间并没有显著差异;而不施磷处理累计气孔限制达到65.7%,显著高于生化限制,这表明缺磷条件下气孔是限制其光合诱导速率的主要因素。[结论]缺磷主要限制了带状复合种植下大豆叶片气孔导度对光照诱导的响应,导致其光合效率和产量下降。因此,合理的磷肥施用对提高带状复合种植体系中大豆在波动光环境下的光合效率,减少产量损失具有重要意义。

[Objective]When intercropping with maize(Zea mays L.),the low-tier crop soybean[Glycine max(L.)Merr.]would suffer yield limitations due to fluctuating light conditions.As phosphorous(P)involves in various physiological processes,we studied the effect of P nutrition on photosynthesis during light induction,trying to enhance soybean photosynthetic efficiency and production potential through P nutrient management.【Method】Field experiments were conducted in Sichuan Agriculture University,the cropping system was maize and soybean intercropping.P fertilizer application(CK)and no application(-P)on soybean was set up as the treatments.At branching stage of soybean,leaf gas exchange parameters,P content,and the relevant physiological parameters were measured under both steady-state light and light-induced processes.The parameters included net photosynthesis rate(A),stomatal conductance(g_(5)),intercellular CO^(2)concentration(C_(i)),transpiration rate(T_(r)),and electron transfer rate(J),as well as P content and photosynthetic pigment levels.Additionally,proportions of stomatal and biochemical photosynthetic limitation factors were calculated.[Results]Compared with CK,-P significantly inhibited the growth of soybean,the grain yield and plant dry weight at maturing stage were reduced by 24.5%and 23.9%,respectively.-P significantly reduced the total and inorganic P contents of leaves at the branching stage,but did not affect the contents of chlorophyll a,chlorophyll b,and carotenoids.Under steady-state saturated light,-P decreased the leaf A and Tr by 30.9%and 39.5%,but did not impact the gs significantly,resulting in a significant increase in C_(i).-P decreased the stomatal limit value of soybean leaves by 16.7%,implying that non-stomatal factors were the dominant factor causing the decrease in A under steady-state saturated illumination.During the induction period of transitioning from low to high light,the induction rates of A and gs in CK were faster than those in-P treatment,while the induction rate of J showed no significant difference between the two treatments.Photosynthetic limitation analysis revealed no significant difference in cumulative stomatal limitation and biochemical limitation during light induction under CK treatment.However,cumulative stomatal limitation reached 65.7%under-P condition,significantly higher than biochemical limitation.It showed that stomata was the main factor limiting its photosynthetic induction rate under phosphorus deficiency conditions.[Conclusions]Phosphorus deficiency mainly limits the response of stomatal conductance of soybean leaves to light induction under strip compound planting,resulting in a decrease in photosynthetic efficiency and yield.Therefore,reasonable phosphorus fertilizer application is of great significance to improve the photosynthetic efficiency of soybeans in soybean-maize strip compound planting under fluctuating light environment and reduce yield loss.