Photosynthetic Acclimation of Shade-Grown Soybean Seedlings to a High-Light Environment

Yahan Su; Huan Yang; Yushan Wu; Wanzhuo Gong; Hina Gul; Yanhong Yan; Wenyu Yang

doi:10.3390/plants12122324

Photosynthetic Acclimation of Shade-Grown Soybean Seedlings to a High-Light Environment

Plants (Basel). 2023 Jun 15;12(12):2324. doi: 10.3390/plants12122324.

Authors

Yahan Su^{1

2}, Huan Yang^{1

2}, Yushan Wu^{1

2}, Wanzhuo Gong³, Hina Gul⁴, Yanhong Yan⁵, Wenyu Yang^{1

2}

Affiliations

¹ College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China.
² Key Laboratory of Crop Eco-Physiology and Farming System in Southwest of China, Sichuan Engineering Research Center for Crop Strip Intercropping System, Chengdu 611130, China.
³ Crop Research Institute, Chengdu Academy of Agricultural and Forestry Sciences, Chengdu 611130, China.
⁴ National Center of Industrial Biotechnology, Arid Agriculture University, Rawalpindi 46300, Pakistan.
⁵ College of Grassland Science and Technology, Sichuan Agricultural University, Chengdu 611130, China.

Abstract

Soybean in relay intercropping is initially exposed to a shade environment, followed by exposure to full sunlight after the harvesting of primary crops, e.g., maize. Therefore, soybean's ability to acclimate to this changing light environment determines its growth and yield formation. However, the changes in soybean photosynthesis under such light alternations in relay intercropping are poorly understood. This study compared the photosynthetic acclimation of two soybean varieties with contrasting shade tolerance, i.e., Gongxuan1 (shade-tolerant) and C103 (shade-intolerant). The two soybean genotypes were grown in a greenhouse under full sunlight (HL) and 40% full sunlight (LL) conditions. Subsequently, after the fifth compound leaf expanded, half of the LL plants were transferred to a high-sunlight environment (LL-HL). Morphological traits were measured at 0 and 10 days, while chlorophyll content, gas exchange characteristics and chlorophyll fluorescence were assayed at 0, 2, 4, 7 and 10 days after transfer to an HL environment (LL-HL). Shade-intolerant C103 showed photoinhibition 10 days after transfer, and the net photosynthetic rate (P_n) did not completely recover to that under a high light level. On the day of transfer, the shade-intolerant variety, C103, exhibited a decrease in net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (E) in the low-light (LL) and low-light-to-high-light (LL-HL) treatments. Additionally, intercellular CO₂ concentration (C_i) increased in low light, suggesting that non-stomatal factors were the primary limitations to photosynthesis in C103 following the transfer. In contrast, the shade-tolerant variety, Gongxuan1, displayed a greater increase in P_n 7 days after transfer, with no difference observed between the HL and LL-HL treatments. Ten days after transfer, the shade-tolerant Gongxuan1 exhibited 24.1%, 10.9% and 20.9% higher biomass, leaf area and stem diameter than the intolerant C103. These findings suggest that Gongxuan1 possesses a higher capacity to adapt to variations in light conditions, making it a potential candidate for variety selection in intercropping systems.

Keywords: acclimation; intercropping; leaf; phenotype; soybean.

Abstract

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