高光、水分和盐胁迫下小麦光合特性和抗氧化酶系统的比较

为了解植物光合机构及抗氧化酶系统对高光、水分及盐胁迫的适应机制，比较分析了光强1 800 μmol·m^-2·s^-1、20% 聚乙二醇（PEG-6000）和0.3 mol·L^-1 NaCl处理下小麦叶绿素荧光以及抗氧化酶活性的变化。结果表明，与对照相比，高光胁迫、水分胁迫和盐胁迫下小麦叶片相对含水量、总蛋白含量以及叶绿素含量均下降，以水分胁迫效应最显著，盐胁迫次之。三种胁迫均显著降低了小麦叶片的光合速率、气孔导度、蒸腾速率、PSII最大光化学效率（F_v/F_m）及电子传递率（ETR），而显著增加胞间CO₂浓度、非光化学淬灭（NPQ）、脯氨酸及可溶性糖含量，也以水分胁迫效应最显著。三种胁迫下小麦叶片内的超氧化物歧化酶（SOD）、过氧化物酶（POD）及过氧化氢酶（CAT）活性随胁迫时间的延长呈现不同的变化趋势。其中，SOD活性在三种胁迫下均呈先升后降的趋势；POD活性在高光和水分胁迫下先升后降，而在盐胁迫下呈上升趋势；CAT活性在高光和盐胁迫下呈上升趋势，而在水分胁迫下呈下降趋势。以上结果表明，在三种环境胁迫中，水分胁迫给小麦带来的伤害最严重，盐胁迫次之，高光胁迫最轻。 此外，小麦抗氧化酶系统在高光胁迫、水分胁迫及盐胁迫下应答机制不同。

Effects of High Light, Water and Salt Stresses on Photosynthetic Characteristics and Antioxidant Enzyme System in Wheat

To investigate the differences in photosynthetic apparatus and antioxidant defense system of higher plants under environmental stresses, chlorophyll fluorescence parameters and the activities of antioxidative enzymes were compared in wheat(Triticum aestivum L.) seedlings exposed to high light, water stress, and salt stress. The results showed that the relative water content(RWC), the amount of total proteins, chlorophyll content,net photosynthesis rate,stomatal conductance,transpiration rate,maximum efficiency of PSII(F_v/F_m), and electron transport rate(ETR) were significantly decreased under three environmental stresses. Compared with the control, water stress resulted in the most significant decrease in RWC and contents of total proteins and chlorophyll. However, the intercellular CO₂ concentration, the non-photochemical quenching, and the contents of proline and soluble sugar significantly were increased in wheat seedlings exposed to three environmental stresses. In addition, the activities of antioxidant enzymes presented different changes under three environmental stresses. Superoxide dismutase(SOD) activity showed a significant decrease in wheat exposed to three severe stresses. Peroxidase(POD) activity was significantly decreased under high light for 3 h and water stress for 72 h, while an obvious increase was observed under salt stress for 72 h. Catalase(CAT) activity was remarkably increased under high light and salt stress, while a significant decline in CAT activity was found under water stress. These results indicated that water stress resulted in the most severe damage to wheat seedlings. Furthermore, antioxidant systems showed the different response to three environmental stresses in wheat.