摘要:盐碱复合胁迫是影响植物生长的主要环境因子。为了探究垂丝海棠（Malus halliana Koehen）响应盐碱复合胁迫的生理特性，利用主成分分析法明确耐盐碱阈值，以2年生垂丝海棠苗为试材，将NaCl与NaHCO₃按1：1的比例混合，通过盆栽浇灌Hogland营养液的方法，模拟5种不同浓度（0、50、100、150、200 mmol/L）盐碱复合胁迫对其光合色素、光合参数、叶绿素荧光参数及渗透调节物质的影响，并对其相关指标进行相关性和主成分分析。结果表明，随着胁迫强度的增大，叶绿素（Chl T）合成受阻，净光合速率（P_n）、气孔导度（G_s）、蒸腾速率（T_r）、胞间CO₂浓度（C_i）、叶片含水量（WC）下降，最大光化学效率（F_v/F_m）、表观光合电子传递速率（ETR）、PSⅡ实际化学效率（φPSⅡ）、光化学猝灭系数（qP）被抑制；类胡萝卜素（Car）含量、水分利用效率（WUE）、电解质外渗率、非调节性能量耗散（Y（NO））升高；胁迫40 d时，初始荧光（F₀）显著升高，而调节性能量耗散Y（NPQ）、非光化学荧光淬灭系数（qN）急剧降低；脯氨酸、可溶性糖、有机酸显著积累，并在100 mmol/L浓度下达到峰值。植株的P_n与G_s、C_i、ETR、φPSⅡ呈极显著正相关，与T_r、WC、qP、Chl T呈显著正相关，与电导率、脯氨酸、Y（NO）呈显著负相关。因此，盐碱复合胁迫下，垂丝海棠叶片主要通过降低G_s、C_i、T_r、WC，提高WUE、大量积累渗透调节物质、启动热耗散机制来保持光合系统伤害与修复的动态平衡。根据主成分分析法，浓度100 mmol/L为耐盐碱阈值，同时G_s、C_i、T_r、Chl T、ETR、φPSⅡ、Y（NO）、WC、qP、电解质渗透率、脯氨酸可作为评价垂丝海棠耐盐碱能力的有效指标。



Abstract:Saline-alkali stress is a major environmental factor limiting plant growth. To investigate physiological response of Malus halliana to saline-alkali stress and screen the threshold of saline-alkali tolerance, the characteristics of photosynthetic pigments, chlorophyll fluorescence parameters and osmolytes were studies and multiple indices were analyzed by correlation analysis and principal component analysis (PCA). Two-year-old of M. halliana was employed as experiment materials, and 5 different concentrations of saline-alkali stress (0, 50, 100, 150, 200 mmol/L) were simulated on the basis of NaCl and NaHCO₃ (1:1) by pot experiment. The results showed that:with the increaseing of salt concentration, the chlorophyll content (Chl T), net photosynthesis (P_n), stomatal conductance (G_s), transpiration rate (T_r), intercellular CO₂ concentration (C_i), leaf water content (WC), maximal photochemical efficiency (F_v/F_m), photosynthetic electron transport rate (ETR), actual photochemical efficiency (φPSⅡ) and photochemical quenching coefficient (qP) were decreased, whereas the carotenoid content (Car), water use efficiency (WUE), electrolyte leakage rate and non regulatory energy dissipation (Y(NO)) were increased. After 40 d stress, the initial fluorescence (F₀) increased significantly but regulatory energy dissipation (Y(NPQ)) and non photochemical quenching coefficient (qN) decreased significantly. However, the content of proline, soluble sugar and total organic acid remarkablely accumulated and reached the maximum at salinity 100 mmol/L. The P_n of M. halliana had a positive relation with G_s, C_i, ETR, φPSⅡ, T_r, WC, qP and Chl T, while it correlated negatively with electrolyte leakage rate, proline and Y(NO). In summary, dynamic balance of photosynthetic system between injury and repair of M. halliana leaves was kept by reducing G_s, C_i, T_r and WC, increasing WUE, accumulating a large amount of osmotic regulators and starting heat dissipation mechanism under saline-alkali stress. Based on PCA, the concentration of 100 mmol/L was the critical threshold for saline-alkali tolerance. Moreover, the G_s, C_i, ETR, φPSⅡ, T_r, WC, qP and Chl T, electrolyte leakage rate, proline and Y(NO) could be used as effective indices to evaluate saline-alkali resistance. This study provided a theoretical basis for clarifying the critical threshold of saline-alkali tolerance in M. halliana.





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