Yao Xingdong, Zhou Hongli, Zhu Qian, Li Chunhong, Zhang Huijun, Wu Jun-Jiang, Xie Futi
Soybean Research Institute, Shenyang Agricultural University, Shenyang, China.
Key Laboratory of Soybean Cultivation of Ministry of Agriculture, Soybean Research Institute, Heilongjiang Academy of Agricultural Sciences, Harbin, China.
Front Plant Sci. 2017 Sep 28;8:1695. doi: 10.3389/fpls.2017.01695. eCollection 2017.
In maize-soybean intercropping system, soybean plants will be affected by the wide light-fluctuation, which resulted from the shading by maize plants, as the shading of maize the light is not enough for soybean in the early morning and late afternoon, but at noon, the light is strong as the maize shading disappeared. The objective of this study is to evaluate the photosynthetic response of soybean leaf to the wide light-fluctuation. The data of diurnal variation of photosynthetic characters showed that the photosynthetic rate of intercropped soybean was weaker than that of monocropped soybean. The chlorophyll content, ratio of chlorophyll a/b, and AQE (apparent quantum efficiency) were increased and (dark respiration rate) was decreased for the more efficient interception and absorption of light and carbon gain in intercropping. δ (The efficiency/probability with which an electron from the intersystem electron carriers was transferred to reduce end electron acceptors at the PSI acceptor side) and φ (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) in intercropped soybean leaf were lower compared to those in monocropped one, which showed that the acceptor side of PSI might be inhibited, and also it was the main reason that soybean plants showed a low photosynthetic capacity in intercropping. ψ (the efficiency/probability with an electron moves further than Q) in monocropping and intercropping decreased 5.8, and 35.7%, respectively, while φ (quantum yield for electron transport) decreased 27.7 and 45.3% under the high radiation at noon, which suggested that the acceptor side of PSII was inhibited, while the NPQ became higher. These were beneficial to dissipate excess excitation energy in time, and protect the photosynthetic apparatus against photo-damage. The higher performance index on the absorption basis (PI) and lower δ, φ, ψ, and φ of intercropped soybeans compared to monocropping under high radiation indicated that the electron transfer of intercropped soybean was inhibited more seriously and intercropped soybean adjusted the electron transport between PSII to PSI to adapt the light-fluctuation. Higher NPQ capacity of intercropped soybeans played a key role in keeping the leaf with a better physiological flexibility under the high radiation.
在玉米-大豆间作系统中，大豆植株会受到因玉米植株遮荫导致的光照大幅波动的影响。由于玉米的遮荫，清晨和傍晚时分大豆所获光照不足，但中午时，随着玉米遮荫消失，光照变强。本研究的目的是评估大豆叶片对光照大幅波动的光合响应。光合特性日变化数据表明，间作大豆的光合速率低于单作大豆。间作时，叶绿素含量、叶绿素a/b比值和表观量子效率（AQE）升高，暗呼吸速率降低，以便更有效地截获和吸收光能并增加碳同化。与单作大豆叶片相比，间作大豆叶片中的δ（来自电子传递链中电子载体的电子转移至PSI受体侧以还原末端电子受体的效率/概率）和φ（PSI受体侧末端电子受体还原的量子产额）较低，这表明PSI受体侧可能受到抑制，这也是间作大豆植株光合能力较低的主要原因。单作和间作时的ψ（电子传递距离超过Q的效率/概率）分别降低了5.8%和35.7%，而在中午高辐射下，φ（电子传递量子产额）分别降低了27.7%和45.3%，这表明PSII受体侧受到抑制，同时非光化学淬灭（NPQ）升高。这些有利于及时耗散过剩的激发能，保护光合机构免受光破坏。与单作相比，间作大豆在高辐射下具有更高的基于吸收的性能指数（PI）以及更低的δ、φ、ψ和φ，这表明间作大豆的电子传递受到更严重的抑制，且间作大豆通过调整PSII至PSI之间的电子传递来适应光照波动。间作大豆较高的NPQ能力在使其叶片在高辐射下保持更好的生理柔韧性方面发挥了关键作用。
