摘要
摘要:为明确谷子光合作用以及抗旱生理过程对高大气CO₂浓度和干旱交互作用的响应机制，在开顶式气室中（OTC）开展大气CO₂浓度和干旱交互对谷子影响的研究。设置两个CO₂浓度：环境CO₂浓度（400 μmol·mol^-1）和高CO₂浓度（600 μmol·mol^-1）；两个水分处理：正常水分（70%~80%田间持水量）和干旱（45%~55%田间持水量），对高CO₂浓度和干旱互作下谷子光合气体交换参数、荧光动力学参数及抗旱相关生理指标的变化进行了研究。结果表明：高CO₂浓度可降低干旱条件下光合色素含量，加剧孕穗期谷子气孔关闭，减轻灌浆期干旱对谷子净光合速率的负效应并增加其水分利用效率。孕穗期高CO₂处理使正常水分处理下谷子气孔导度下降66.7%，而干旱处理下减少77.7%；灌浆期高CO₂使正常水分处理和干旱处理下谷子净光合速率分别增加19.0%和87.7%，水分利用效率增加37.1%和39.2%。干旱处理显著降低谷子除非光化学淬灭系数（NPQ）以外所有荧光动力学参数值，灌浆期高CO₂能缓解该作用。高CO₂处理显著减少纤维素含量和正常水分处理下过氧化物酶活性。干旱极显著升高POD活性（高CO₂浓度）及脯氨酸含量、可溶性总糖、淀粉含量（环境CO₂浓度）和纤维素含量（高CO₂浓度）。因此CO₂浓度升高能够改善谷子的PSⅡ光化学效率和提高抗氧化酶活性来增强谷子的抗旱性。
关键词:干旱/
高大气CO₂/
光系统Ⅱ效率/
抗逆性
Abstract:There is a lack of knowledge on the interactive effects of elevated atmospheric carbon dioxide (CO₂) concentrations ([CO₂]) and drought on the photosynthesis and physiological processes underlying foxtail millet drought resistance. An experiment was conducted in an open-top chamber with two CO₂ treatments, ambient [CO₂] (CK, 400 μmol·mol^-1) and elevated [CO₂] (ECO₂, 600 μmol·mol^-1), and two water treatments, normal water (relative water content was 75%-85% soil capacity) and drought (relative water content was 35%-45% soil capacity). We quantified the interactive effects of elevated CO₂ and drought on the gas exchange parameters, fluorescence parameters, and drought-resistant physiological indicators in millet. The results showed that elevated CO₂ could reduce the content of photosynthetic pigment under drought conditions. Elevated [CO₂] aggravated millet stomatal closure at the booting stage, alleviated the negative effects of drought on the net photosynthetic rate at the filling stage, and increased the water utilization efficiency. During the booting stage, elevated [CO₂] resulted in a 66.7% reduction in stomatal conductance under normal water conditions and a 77.7% reduction under drought conditions. During the grouting period, under normal water conditions, elevated [CO₂] led to a 19.0% increase in the grain net photosynthetic rate and a 37.1% increase in water use efficiency; under drought conditions, it led to an 87.7% increase in the grain net photosynthetic rate and a 39.2% increase in water use efficiency, respectively compared with that of ambient [CO₂]. Drought significantly reduced all of the millet fluorescence kinetic parameters, except non-photochemical quenching (NPQ), and elevated [CO₂] alleviated this effect in the grouting period. At the booting stage, ECO₂ and drought showed significant interactive effects on the intrinsic efficiency of photosystem Ⅱ (PSⅡ) (F_v/F_m'), PSⅡ photochemistry (ΦPSⅡ), and the highest photosynthetic electron transport (ETR) and photochemical quenching coefficient (qP). Elevated [CO₂] significantly reduced the content of cellulose and activity of peroxidase (POD) under normal water conditions. POD activity (under ECO₂), and contents of proline, soluble total sugar, starch content (under CK), and the cellulose content (under ECO₂) were significantly increased under drought conditions. We conclude that elevated [CO₂] can enhance the drought resistance of C₄ foxtail millet by improving the photochemical efficiency of photosystem Ⅱ and the activity of antioxidant enzymes.
Key words:Drought/
Elevated CO₂ concentration/
PSⅡ efficiency/
Stress resistance



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