盐胁迫对西南卫矛生长及光合特性的影响

以西南卫矛(Euonymus hamiltonianus Wall. ex Roxb.)为试材,设置4个NaCl质量浓度(0、2.0、4.0、6.0 g·L^-1)处理,通过对其叶片光合气体交换参数(净光合速率、蒸腾速率、气孔导度和细胞间CO₂浓度)、生物量、相对电导率、叶绿素含量及叶绿素荧光动力学特征的测定,分析了盐胁迫对西南卫矛生长与光合特性的影响。结果表明:与对照相比, 2.0、4.0、6.0 g·L^-1盐浓度处理下西南卫矛净光合速率、蒸腾速率、气孔导度、气孔限制值和水分利用效率显著降低,胞间二氧化碳浓度显著升高,叶片最大光化学效率和单位面积有活性的反应中心数目均显著降低, OJIL曲线中K点和J点均大幅上升,叶绿素含量显著降低; 2.0 g·L^-1盐浓度处理下西南卫矛根冠比和相对电导率与对照差异均不显著,而4.0、6.0 g·L^-1盐浓度处理下西南卫矛根冠比和相对电导率显著升高。表明西南卫矛对低浓度盐胁迫有一定的耐受能力,但高浓度盐胁迫会对西南卫矛造成影响,抑制PSⅡ活性,降低光化学效率,降低植株对营养物质的吸收和利用,使植株的生长受到阻碍甚至死亡。

Effects of salt stress on the growth and photosynthetic production of Euonymus hamiltonianus

A potted experiment was conducted to explore the effects of salt stress on seedling growth and photosynthetic characteristics of Euonymus hamiltonianus. The biennial seedlings were exposed to different contents of NaCl solutions (0, 2.0, 4.0, 6.0 g·L^-1) for 30 days. The photosynthetic gas exchange parameters [i.e. net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO₂ concentration (Ci)], biomass properties, relative electrical conductivity, pigment contents and kinetic characteristics of chlorophyll fluorescence were measured, aiming to investigate the adaptation mechanism to salt stress of E. hamiltonianus. The results showed that: Compared with CK, salt stress induced a significant decrease of Pn, Tr, Gs, limiting value of stomata(Ls) and water use efficiency (WUE), whereas it caused by a marked increase of Ci under different NaCl solutions in E. seedlings. The maximum photochemical efficiency (F_v/F_m) and the number of active reaction centers per unit area (RC/CS_m) in the blade were reduced under saline treatments compared to that of in the controls, and both of the F_v/F_m and RC/CS_m got significant differences. The points of K to J in the OJIL curve were increased and reached markedly differences, while the pigments contents were significantly decreased, induced by the salt conditions. Besides, compared with CK, the root-shoot ratio (R/S) and Ec had no obvious difference in the treatment of 2.0 g·L^-1, while they were significantly higher in treatments of 4.0, 6.0 g·L^-1. In conclusions, from the above results we could conclude that E. hamiltonianus had cer-tain tolerance to low concentration of salt stress, but higher NaCl concentration could suppressed seedling growth for it inhibited the activity of PSⅡ, reduced photosynthetic performance and use efficiency of mineral nutrients, resulting in a poor growth and even death of the plants.