脱叶剂对棉花叶片叶绿素荧光动力学参数的影响

利用叶绿素荧光动力学测定技术,对脱叶剂的不同喷施时间条件下棉花叶片光能吸收、传递、转换特性及棉花产量进行了研究。结果表明喷施脱叶剂降低了棉花叶片的光合功能,降低了最大光化学效率(Maximum photochemical efficiency,Fv/Fm)及PSⅡ反应中心开放部分的比例,使初始荧光(Minimal fluorescence,Fo)上升、光合电子传递速率(Electron transport rate,ETR)和PSⅡ总的光化学量子产量(Photosynthetic quantum yield,Yield)降低,提高了非光化学猝灭系数(Non-radiant energy,NPQ),说明脱叶剂胁迫下棉花叶片发生了光抑制,PSⅡ复合体受到损伤伴随着光合电子传递受阻。吐絮率10%时喷施脱叶剂使棉花铃重、衣分、皮棉产量显著低于对照。吐絮率50%时喷施脱吐隆300 g·hm~(-2)+40%乙烯利1200 m L·hm~(-2),第25天棉花脱叶率为90.1%,吐絮率为99.87%,对棉花铃重、衣分及皮棉产量影响最小且更有利于促进叶片脱落和棉铃成熟。

Effect of Defoliants on Chlorophyll Fluorescence of Cotton Leaves

To explore the physiological mechanism of defoliating cotton leaves under different spraying times, we investigated the absorption, transmittance, and transformation of solar radiation by cotton leaves using the chlorophyll fluorescence determination method. Results show that the applied defoliant reduced cotton leaf photosynthesis, maximum photochemical efficiency, photosynthetic electron transport rate and photosynthetic quantum yield, but increased minimal fluorescence and dissipation of non-radiant energy, which indicates that cotton leaves might experience some degree of photosynthetic protection under defoliant stress. Compared with thidiazuron, Dropp Ultra (Bayer, Germany) is more effective in accelerating the process of cotton leaf senescence. When a defoliant was applied to cotton when the boll opening rate reached 10%, boll weight, lint percentage, and lint yield were significantly lower than the contro (spraying water)l. When spraying the plants with Dropp Ultra 300 g·hm^－2 + 40% ethylene 1200 mL·hm^－2 when the boll opening rate reached 50%, the rate of shed leaves was 90.1% and the boll opening rate was 99.87% after a period of 25 days, which indicates this application has minimal impact on cotton boll weight, lint percentage, and lint yield, and is more conducive to the promotion of mature bolls and defoliation.