5-氨基乙酰丙酸对NaCl胁迫下番茄幼苗光合特性的影响

为探讨5-氨基乙酰丙酸（ALA）对NaCl胁迫下番茄光合特性的调控作用，以‘金鹏一号’番茄幼苗为试材，研究叶面喷施50 mg·L^-1或根施10 mg·L^-1 ALA对100 mmol·L^-1 NaCl胁迫下番茄幼苗光合及叶绿素荧光参数的影响.结果表明： NaCl胁迫下，番茄幼苗光合气体交换参数（净光合速率P_n、气孔导度g_s、胞间CO₂浓度C_i、蒸腾速率T_r）及叶绿素荧光参数（实际光化学量子产量F_v′/F_m′、F_m′、PSⅡ反应中心实际光化学效率Φ_PSⅡ、表观光合电子传递效率ETR、光化学淬灭q_P、光化学反应Pc）均显著降低，根施或叶施ALA均可以提高NaCl胁迫下番茄叶片的光合能力，但两种处理方式之间存在一定差异.叶面喷施50 mg·L^-1ALA或根施10 mg·L^-1ALA处理均显著提高了番茄叶片P_n、T_r、g_s和C_i，提高了水分利用效率（WUE），显著增加了NaCl胁迫下叶片的最大净光合速率，减轻了光抑制.根施ALA对叶绿素含量的作用效果较好，而叶施ALA对光合参数的作用效果较好，两处理叶绿素荧光参数差异不显著.叶面喷施或根施ALA可以提高番茄幼苗的耐盐性，其调控作用与促进叶绿素合成与稳定、维持正常气孔开闭、降低气孔限制，进而提高NaCl胁迫下番茄叶片的光合能力和PSⅡ光化学效率有关.

Effect of 5-aminolevulinic acid on photosynthetic characteristics of tomato seedlings under NaCl stress.

In this research, the possibility of exogenous application of 5-aminolevulinic acid (ALA) on photosynthetic characteristics of tomato seedlings under NaCl stress was investigated. Five leaves seedlings of tomato (Solanum lycopersicum cv. Jinpeng No.1) were used as starting materials, applied with 50 mg·L^-1 ALA by foliage spray or 10 mg·L^-1 ALA by root soaking to study the changes in their photosynthesis and fluorescence parameters under 100 mmol·L^-1 NaCl. The result showed that, photosynthetic gas exchange parameters (net photosynthetic rate P_n, stomata conductance g_s, intercellular CO₂ concentration C_i,
transpiration T_r) and chlorophyll fluorescence parameters (F_v′/F_m′, F_m′, Φ_PSⅡ, ETR, q_P, Pc) were severely reduced under NaCl treatment and ALA application by foliage spray or root soaking with proper concentrations exerted positive influences on tomato seedlings under salt stress, while there were some differences between foliage spray and root soaking in the influence on chlorophyll content, photosynthesis and chlorophyll fluorescence. Both foliage spray with 50 mg·L^-1ALA and root soaking with 10 mg·L^-1ALA significantly increased P_n, C_i, g_s and T_r of tomato seedlings under NaCl stress, alleviated photosynthetic inhibition. Root application of ALA had a better effect on the chlorophyll content than foliage application. However, the photosynthetic parameters showed that foliage application of ALA had a better effect than root application, and both treatments had no difference in the influence on chlorophyll fluorescence parameters of tomato seedlings. It could be deduced that the regulating effect of ALA on enhancing salt tolerance of tomato seedlings is attributed to its effect on improving chlorophyll biosynthesis and metabolism, increasing stomatal conductance and reducing stomatal limitation, thus, enhancing the photosynthetic capacity and PSⅡ photochemical efficiency of tomato leaves under NaCl stress.