Abstract

Dynamics of chlorophyll a fluorescence changes (including JIP test parameters) and photosynthetic pigments were studied in oat (Avena sativa L.) leaves of late summer sowing during autumnal cooling. As the average daily temperature decreased from 8 to 2°С, the chlorophyll content decreased by 40%, while the chlorophyll a/b ratio ranged between 2.2 and 2.4. The total pool of carotenoids and the relative content of β‑carotene, lutein, neoxanthin, and pigments of the violaxanthin cycle changed insignificantly. The relative number of Q_B-nonreducing reaction centers (RC) of photosystem II (PSII) and the quantum yield of energy-dependent component qE of nonphotochemical quenching in the PSII antenna (φ_NPQ parameter) were found to increase during the seasonal cooling. The values of F_v/F_m parameter characterizing the maximal photochemical efficiency of PSII complexes were 0.72–0.76. At temperatures around 0°C, F_v/F_m decreased to 0.62. At the same time, the nonregulated (light-independent) thermal dissipation (photoinhibitory component qI of nonphotochemical quenching) was enhanced, which was manifested in the increase in parameters φ_Do and DI₀/RC. It is concluded that, under seasonal cooling, the PSII reaction centers partly lose photochemical activity and start functioning as dissipative centers of excitation energy. In a significant part of inactivated RC, the loss of Q_A-reduction was reversible, which implies the formation of photoinactivated forms of PSII complexes stabilized at low temperatures. The decrease in daily average temperatures to −3°С with nighttime low temperatures from −7 to −8°С led to plant death within 3 days.

中文翻译：

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温度秋季降低春燕麦叶片光系统II的功能条件。

摘要

研究了夏末播种在秋季降温期间燕麦（Avena sativa L.）叶片中叶绿素a荧光变化（包括JIP测试参数）和光合色素的动力学。随着日平均温度从8降到2°C，叶绿素含量降低40％，而叶绿素a / b比率在2.2和2.4之间。类胡萝卜素的总含量以及β-胡萝卜素，叶黄素，新黄嘌呤和紫黄质循环色素的相对含量变化不明显。光子系统II（PSII）的Q _B-非还原反应中心（RC）的相对数量和PSII天线中非光化学猝灭的能量依赖成分qE的量子产率（φ发现_NPQ参数在季节性降温期间增加。表征PSII复合物的最大光化学效率的F _v / F _m参数值为0.72-0.76。在0°C左右的温度下，F _v / F _m降至0.62。与此同时，在非管制（光独立的）热耗散（光抑制部件齐非光化学淬灭）的增强，这是在参数φ的增加表现_待办事项和DI ₀/ RC。结论是，在季节性冷却下，PSII反应中心部分失去光化学活性，并开始充当激发能的耗散中心。在大部分失活的RC中，Q _A还原的损失是可逆的，这意味着形成了在低温下稳定的光灭活形式的PSII复合物。每日平均温度下降至−3°С，夜间低温从−7降至−8°С，导致三天内植物死亡。