Effect of Shading on Soybean Leaf Angle and Photosynthetic Characteristics
[Objective]The leaf angle directly affects the utilization of light energy.This study aimed to explore the effects of shading on the leaf angle and photosynthetic characteristics of different shade-tolerant soybean varieties to reveal how leaves can enhance their light interception ability and photosyn-thetic efficiency.[Method]We selected the shade-tolerant variety Nandou25(ND25)and the shade-intolerant variety Gongdou(GD)for the study.We established a normal light treatment(600 μmol/(m²·s),CK)and a low light treatment(300 μmol/(m²·s),L).The responses of plant morphology,dynamic changes in leaf inclination,anatomical structure of the pulvinus,and photosynthetic fluorescence charac-teristics to shade were investigated.[Result]Under the L treatment,the plant height and petiole length of both ND25 and GD significantly increased compared to CK,while the daily mean leaf inclination decreased by 337.26%and 478.83%,respectively.The leaf inclination ranges for ND25 under CK and L treatments were 49.46° and 56.96°,respectively;for GD,they were 33.16° and 73.37°,respectively.The shade-tolerant soybean ND25,compared to CK,showed an increase of 1.12%in the ratio of cortex to pulvinus and 15.38%in the number of flexor muscle cell layers under L treatment,whereas the shade-intolerant GD did not exhibit this significant change.Compared to CK,the transpiration rate,chlorophyll-a content,and chlorophyll-b content of both ND25 and GD increased under L treatment,while the net photosynthetic rate and intercellular CO2 concentration decreased.Moreover,the carotenoid content increased by 481.25%and decreased by 58.97%,respectively.Under L treatment,the photochemical quenching coefficients of both ND25 and GD decreased,and the maximal PSⅡ photochemical efficiency in the dark increased.The photo-chemical efficiency yield of PSⅡ in the light and the non-photochemical quenching coefficient of ND25 de-creased,while those of GD increased.[Conclusion]Under shaded conditions,the range of leaf inclina-tion increases and the daily mean leaf inclination decreases.Shade-tolerant soybeans increase the ratio of cortex to pulvinus and the number of flexor cell layers to orient leaf inclination perpendicular to incident light,thereby enhancing light energy interception.
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