2,4-表油菜素内酯对干旱胁迫下垂丝海棠生理特性的影响

以7～8叶龄的垂丝海棠实生苗为试验材料，研究外源喷施2,4-表油菜素内酯（EBR）对干旱胁迫下垂丝海棠幼苗光合及生理特性的影响。采用盆栽控水法，设置CK（正常水分）与干旱胁迫加6种浓度油菜素内酯处理，即T1(0 mg·L^-1)、T2(0.20 mg·L^-1)、T3(0.40 mg·L^-1)、T4(0.60 mg·L^-1)、T5(0.80 mg·L^-1)和T6(1.00 mg·L^-1),分别测定各处理下叶绿素含量、光合特性、抗氧化酶活性及渗透调节物质含量，并进行相关性与主成分分析。随干旱胁迫时间的延长，垂丝海棠叶片的Chl a、Chl b、Chl a+b、Chl a/b、净光合速率（P_n）、气孔导度（G_s）和蒸腾速率（T_r）均呈下降趋势；胞间CO₂浓度（C_i）、丙二醛（MDA）含量和相对电导率（REC）呈上升趋势；脯氨酸（Pro）含量、超氧化物歧化酶...

Effects of 2,4-Epibrassinolide on physiological characteristics of Malus halliana under drought stress

The effects of exogenous 2,4-Epibrassinolide (EBR) on the photosynthesis and physiological characteristics of Malus halliana seedlings under drought stress with seedlings of 7~8 leaf\|age Malus halliana as experimental materials were studied. The experiment used pot water control method of CK (normal water level) and drought stress as well as 6 brassinolide concentrations of T1 (0 mg·L^-1), T2 (0.2 mg·L^-1), T3 (0.4 mg·L^-1), T4 (0.6 mg·L^-1), T5 (0.8 mg·L^-1) and T6 (1 mg·L^-1). The contents of chlorophyll, photosynthetic characteristics, antioxidant enzyme activity, relative electrical conductivity and osmotic regulating substances in each treatment were measured, and the correlation and principal component analysis were computed. With the extension of drought stress time, Chl a, Chl b, Chl a+b, Chl a/b, net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r) decreased, and intercellular CO₂ concentration (C_i), malonaldehyde (MDA), relative electrical conductivity (REC) increased. The activities of proline (Pro), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased first and then decreased. Additionally, compared with the control group, the increase and decrease of each index of Malus halliana leaves decreased to different degrees after spraying different concentrations of exogenous brassinolide, and there was a concentration effect. Among them, under 0.2 mg·L^-1 (T2) treatment, Chl a, Chl b, Chl a+b, Chl a/b, P_n, G_s and TR decreased the least, significantly higher than those in T1, while MDA and REC increased the most, which were significantly higher than those in T1. Subsequently, correlation analysis of 14 indexes showed that P_n was significantly positively correlated with Chl a, Chl b, Chl a+b, Chl a/b and G_s (P<0.01) and T_r (P<0.05), and negatively correlated with REC and C_i (P<0.01). In addition, the 14 indexes were analyzed by principal component analysis, and the two principal components with eigenvalue >1 were extracted, whose eigenvalues were 9.765 and 3.747, respectively. The variance contribution rates were 69.747% and 26.766%, respectively, and the cumulative variance contribution rate reached 96.513%, which met the requirements. Finally, according to the ranking of principal component scores, the alleviating ability of exogenous brassinolide to drought stress of Malus halliana was T2>T3>T4>T5>T6>T. The 0.2 mg·L^-1 brassinolide treatment had better results in improving the photosynthetic capacity, enhancing the activity of antioxidant enzymes, and promoting the stability of membrane to alleviate drought stress.