莴笋叶片低温下积累花青素对光合作用的影响

【目的】探讨冬季低温环境下莴笋叶片花青素积累对光合作用的影响及作用机理，以期为莴笋栽培和品种选育提供参考依据。【方法】分别于常温季（10月中旬）、冬季低温初期（11月底—12月初）、中期（翌年1月中旬）和末期（翌年2月上旬）在广西大学试验基地活体监测莴笋叶片叶绿素荧光和光合气体交换特性，采用分光光度法测定过氧化氢（H₂O₂）浓度、超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性和花青素含量。【结果】与常温季相比，低温初期叶片凌晨最大光化学效率值（F_v/F_m）略降，基底荧光（F_o）略增，相对电子传递速率（ETR）下降8.9%，光化学耗散（qP）、光化学途径能耗效率占比［Y（Ⅱ）］和稳态净光合速率（P_n）略降，最大净光合速率（P_max）则下降3.59μmol/（m2·s）；SOD和POD活性分别增加5倍和1倍，CAT活性降低31%；H₂O₂和花青素含量分别增加81%和9倍。到低温中期时，F_v/F_m升至0.85，F_o、ETR、Y（II）、P_n和P_max回升至略高于常温季水平；SOD和CAT活性较初期增加1倍；H₂O₂含量略降，花青素含量增至初期的7倍。末期天气转暖时，F_v/F_m降至0.77，F_o上升到接近0.10的峰值，组成型能量耗散率［Y（NO）］占比高达34%，ETR、P_n和P_max比中期分别降低22%、28%和33%；尽管SOD、POD和CAT活性在中期的基础上分别增加178%、28%和36%，而H₂O₂含量依然剧增1.36倍；花青素含量上翻了3倍。相关分析的结果表明，花青素含量、SOD活性和H₂O₂含量两两间呈显著正相关（P< 0.05），而花青素、H₂O₂含量和光合速率之间相关性均不显著（P> 0.05），光合速率是多因素综合作用的结果。【结论】与单独低温作用相比，低温和强光共同作用下莴笋叶片合成更多花青素，通过增加叶片温度、调节叶片能量平衡及与抗氧化系统共同作用等方式起光保护作用，为低温下光合机构功能维持及良性运转提供支撑。

Effects of anthocyanin accumulation on photosynthesis in leaves of asparagus lettuce under low temperature

【Objective】To investigate the effects of anthocyanin accumulation on photosynthesis and its mechanism in the asparagus lettuce leaves at low temperature in winter, and provide reference basis for asparagus lettuce cultivation and breeding.【Method】The seedlings grown in the experimental field in Guangxi University were taken as test materials, and the chlorophyll fluorescence, photosynthetic gas exchange characteristics were measured on the living plants in the field at the normal temperature season(middle October), the early chill season(late November-early December), middle chill season(middle January in next year) and late chill season(early February in next year) in winter respectively, and then, the sample leaves were taken back to laboratory.Hydrogen peroxide(H₂O₂) concentration, superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) activities and anthocyanin contents were determined by spectrophotometry in those leaves.【Result】Compared with the normal temperature season, predawn maximal photochemical efficiency of PSⅡ(F_v/F_m) value in asparagus lettuce leaves decreased, and the ground fluorescence(F_o) value increased slightly at the earlychill season.At the same time, the apparent photosynthetic electron transport rate(ETR) value decreased by 8.9%, and the photochemical quenching coefficient(qP), actual PSII photochemical efficiencyY(Ⅱ)], stable net photosynthetic rate(P_n) values were decreased slightly, and the maxim photosynthesis rate(P_max) decreased by 3.59 μmol/(m2·s).SOD and POD activity increased by 5 times and once respectively, yet CAT activity decreased by 31%.H₂O₂ and anthocyanin contents increased by 81% and 9 times respectively at this period.During the middle chill season, F_v/F_m value increased to 0.85, F_o, ETR, Y(II), P_n and P_max values also increased to be slightly higher than that at the normal temperature season.SOD and CAT activities increased by one time, and H₂O₂ content was slightly decreased, however, anthocyanin contents raised by 7 times compared with early stage.At the end of the chill season, with the warming up of the weather, F_v/F_m value decreased to 0.77.Both F_o(0.1) and the non-regulatory energy dissipation Y(NO) (34%) value raised to the highest level.The values of ETR, P_n and P_max decreased by 22%, 28% and 33%.Although SOD, POD and CAT activity increased by 178%, 28% and 36%, H₂O₂ concentration increased by 1.36 times of that at the middle chill season.Anthocyanin concentration also increased by 3 times of that at the middle chill season.Across the normal and the chill season, anthocyanin contents had significant positive correlation with H₂O₂ concentrations, and H₂O₂ concentrations had positive correlation with SOD activities(P< 0.05).Moreover, there were no significant positive correlations between P_n values and anthocyanin contents and H₂O₂ concentrations(P> 0.05). P_n was affected by multiple factors.【Conclusion】The combined effects of low temperature with strong light synthetize more anthocyanin in asparagus lettuce leaves compared with low temperature alone.It maintains the photosynthetic apparatus running in its right track through increasing leaf temperature, regulating energy balance and increasing antioxidant ability under the chilling stress, which provides support for maintenance and functio-ning of photosynthetic apparatus under low temperature.