模拟酸雨对德保苏铁叶片光合作用及根系分泌有机酸的影响

Effects of simulated acid rain on photosynthesis of leaves and organic acid secreted by roots of Cycas debaoensis Y. C. Zhong et C. J. Chen

【目的】研究酸雨胁迫下德保苏铁根系分泌有机酸及叶片光合生理变化特征,为德保苏铁的保护提供参考。【方法】针对德保苏铁分布地(广西德保)的降雨特点,采用喷淋模拟酸雨的方法研究土培德保苏铁的根系分泌有机酸和光合生理的变化特征。【结果】在pH2.1的模拟酸雨胁迫下,土壤pH值降低,德保苏铁叶片出现枯斑,叶片净光合速率、气孔导度、蒸腾速率、胞间CO2浓度均受到严重影响;在德保苏铁根系分泌的有机酸中主要检测出草酸,中强度酸雨(pH4.2和pH3.1)对德保苏铁根系分泌草酸的影响不大,而强酸雨(pH2.1)处理可引起根系分泌草酸含量显著增加。【结论】人工模拟酸雨强度达pH2.1时对德保苏铁叶片造成严重伤害,其光合作用也随之减弱;德保苏铁根系通过分泌更多的有机酸来增加对强酸雨胁迫的适应性和抗逆性。德保苏铁原产地土壤对中轻度酸雨胁迫具有一定的缓冲能力,但当酸雨强度过大时仍会导致其土壤严重酸化。

[ Objective ]Effects of acid rain on photosynthesis changes of leaves and organic acid secreted by roots of Cycas debaoensis were studied to better protect Cycas debaoensis. [ Method ]According to the rainfall characteristics in Guangxi, simulated acid rain spraying was adopted to investigate changes in organic acid secreted by roots and photosyn- thetic physiology. [Result]Under pH 2.1 acid rain stress, soil pH decreased, the plant leaves showed necrotic lesion, and net photosynthetic rate, stomatal conductance, transpiration rate and the plant intercellular C02 concentration in leaves were all seriously impacted. Oxalic acid was the main organic acid detected from the roots of Cyeas debaoensis. The oxalic acid secreted by the roots of Cycas debaoensis showed no change under moderate acid rain stress （pH 4.2 and pH 3.1）, but obviously increased under strong acid rain stress（pH 2.1 ）. [Conclusion]Simulated acid rain with pH 2.1 severely dam- aged the leaves of Cycas debaoensis, and weakened their photosynthesis. In response, Cycas debaoensis roots had to se- crete more organic acid to adapt and resist overwhelming acid rain stress.