Effect of Salt Stress on Photosynthetic GasExchange and Chlorophyll FluorescenceParameters in Alhagi pseudalhagi

Soil salinity is one of the most important environmental factors limiting plant growth and productivity in many regions in the world. Salt stress directly affects plant photosynthesis, which is an important physiological process to limit plant growth and crop yield. But the effects of salt stress on the mechanism of the photosynthesis is still not clear. In this experiment, the salt tolerant plant Alhagi pseudalhagi was selected as the experiment material, and the salt sensitive plant Vigna radiata as the control, to explore the effects of salt stress on photosynthetic parameters of A. pseudalhagi. Plants were grown in a greenhouse,cultured with 1/2 Hoagland nutrient solution, treated by 0(control), 50, 100 or 200 s of mmol/L of NaCl solution for 12 d. Then,the chlorophyll contents, gas exchange parameters and chlorophyll a fluorescence in each treatment were measured. The results showed that under the salt stress simulated by 50 mmol/L NaCl, the net photosynthetic rate(Pn) and stomatal conductance(gs)of A. pseudalhagi were significantly increased compared with the control, while intercellular CO_2 concentration(Ci) was significantly decreased, Fv'/Fm', Fv/Fm and Fv/Fo were increased over time, but had no significant differences with the control ФPSⅡ,ETR and qP were significantly increased, and NPQ was significantly decreased. Under the salt stress simulated by 100 and 200mmol/L NaCl, Fv'/Fm', Fv/Fm, Fv/Fo, ФPSⅡ and qP of A. pseudalhagi were gradually decreased over time. In contrary, under the salt stress simulated by 50 and 100 mmol/L NaCl, the Pn, gs, Ci, Fv'/Fm', Fv/Fm, Fv/Fo, ФPSII, qP and ETR were all significantly decreased, while NPQ was significantly increased.

引起核桃种子休眠的主要因素及其休眠类型

【目的】研究核桃种子休眠的成因及类型。【方法】对核桃种子进行短期低温层积、外用赤霉素(GA_3、清水浸泡和清水浸泡加日光暴晒处理,观察种子发芽率、发芽指数和发芽势,并浸提核桃种壳内的水溶性萌发抑制物质进行生物检测。【结果】核桃种子进行短期低温层积及GA_3处理与CK间无显著差异(|U|≤1.96),而浸种15 d和浸种15 d+自然暴晒处理对发芽率、发芽势、发芽指数的促进作用均较其对照有显著提高(|U|≥2.58)。核桃种壳粗浸提液对小麦种子的萌发率及根、芽生长的抑制效应随浓度增加而上升,当浓度达1.5 g/mL时,小麦种子的萌发率和根、芽的生长率分别为对照的26%、6%和5%。【结论】核桃种子内源GA_3/ABA的比值有可能调节其休眠,而水溶性抑制物质和种壳的机械阻碍是调控其休眠的主导因素。确定核桃种子的休眠为生理休眠型和机械障碍休眠型。