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大田条件下,以普通夏玉米(Zea mays)‘泰玉2号’为材料,于授粉后1–20天遮光55%(+S),以大田自然光照条件下生长的玉米作为对照(–S),研究了遮光及恢复过程中玉米植株的光合性能、叶绿体荧光参数、叶黄素循环以及光能分配的变化,初步揭示夏玉米开花后弱光条件下光适应的生理机制,为玉米高产稳产提供理论依据。结果表明,遮光后玉米穗位叶叶绿素含量及可溶性蛋白含量均减少,RuBP羧化酶和PEP羧化酶活性显著降低,导致穗位叶净光合速率(Pn)迅速下降,光饱和点也明显降低;恢复初期Pn迅速升高,光合关键酶活性有所增强。遮光后植株的最大光化学效率(Fv/Fm)、实际光化学效率(ФPSII)显著降低,非光化学淬灭(NPQ)则显著升高,而恢复初期植株穗位叶ФPSII有所升高,表明突然暴露在自然光下的光合电子传递速率明显加快,这与其光合速率及光合酶活性的趋势保持一致;遮光处理对穗位叶叶黄素循环库的大小(紫黄质+花药黄质+玉米黄质(V+A+Z))影响不显著,但使叶黄素循环的脱环氧化状态(A+Z)/(V+A+Z)增加;遮光后植株分配于光化学反应的光能明显减少,天线耗散光能比率显著增加,恢复过程中植株主要以过剩非光化学反应的形式耗散过剩的光能。遮光后及恢复初期,玉米植株的PSII原初光化学活性明显下降,限制了光合碳代谢的电子供应从而抑制了光合作用,主要依赖叶黄素循环途径进行能量耗散,而在光照转换后遮光的玉米叶片在适应自然光过程中的光保护机制不断完善,光合能力逐渐得到恢复。
Under field conditions, Zea mays ’Taoyu 2’ was used as the material, and the photosynthetic rate was 55% (+ S) after 1 to 20 days of pollination. The maize ) Were used to study the photosynthetic characteristics, chloroplast fluorescence parameters, lutein cycling and light energy allocation of maize plants during shading and recovery. The physiological mechanisms of light adaptation in low light conditions were revealed after summer maize flowering. Provide a theoretical basis. The results showed that chlorophyll content and soluble protein content decreased after mashing, and the activities of RuBP carboxylase and PEP carboxylase decreased significantly, which led to the rapid decrease of Pn and the decrease of light saturation point In the early stage of restoration, the Pn rapidly increased and the key enzyme activity of photosynthesis increased. The maximum photochemical efficiency (Fv / Fm), the actual photochemical efficiency (ФPSII) and the non-photochemical quenching (NPQ) of shading plants significantly increased after shading, while ФPSII of ear leaves at the initial stage of restoration was increased, indicating a sudden exposure The photosynthetic electron transfer rate was significantly accelerated under natural light, which was consistent with the trend of its photosynthetic rate and photosynthetic enzyme activity. The shading treatment had no effect on the size of lutein cycle library (violaxanthin + arnoxanthin + zeaxanthin (A + Z) / (V + A + Z) of the lutein cycle increased. The light energy of the photochemical reaction was significantly reduced after shading , The antenna energy dissipation ratio of light energy increased significantly. During the recovery process, the plant mainly dissipated excess light energy in the form of excess non-photochemical reaction. After shading and early restoration, the photochemical activity of PSII in maize plants decreased significantly, limiting the electron supply of photosynthetic carbon metabolism and thus inhibiting the photosynthesis, mainly relying on the lutein recycling pathway for energy dissipation. However, the light-shielded maize The mechanism of photoprotection of leaves in adapting to natural light continued to improve, and photosynthetic capacity gradually recovered.