干旱胁迫和复水对浙江楠光合与根系生长的影响

Effects of drought stress and re-watering on photosynthesis and root growth of Phoebe chekiangensis

为探索珍贵树种斑块化混交造林的可行性,以浙江楠为研究对象,通过干旱胁迫和复水试验,分析其光合生理特征、根系生长和抗氧化系统的响应。结果表明,对照条件下浙江楠的光合生理最优,重度干旱严重影响浙江楠的生理进程,具体表现为光合能力、光适应特征、瞬间气体交换参数和叶绿素荧光参数的显著下降,其光合速率的下降是由气孔因素导致;中度干旱条件下的浙江楠植株水分利用率最高,重度干旱条件下的水分利用率与对照、中度干旱相比较,分别下降了29.6%和46.4%;中度干旱条件下根半径下降,但SOD、POD和CAT未显著下降, CAT均值略有上升,重度干旱条件下的3种保护酶均表现出显著下降,抗氧化酶已不能有效清除掉活性氧物质。因此,浙江楠具备一定的抗旱能力,中度干旱并不影响浙江楠的正常生长,在实际斑块化造林过程中,可适度控制土壤含水量,有利于在不同树种斑块化混交配置应用中提升浙江楠造林的成活率和保存率。

In this study, the effects of drought stress and re-watering on the photosynthetic and physiological characteristics, root growth, and antioxidant system response of Phoebe chekiangensis were investigated to explore the feasibility of mixed-patch afforestation of economically valuable and endangered tree species. Results showed that photosynthesis by P. chekiangensis was optimal under control conditions, whereas severe drought significantly impaired physiological processes in P. chekiangensis, including photosynthetic capacity, light adaptation characteristics, instantaneous gas exchange parameters, and chlorophyll fluorescence parameters. The decreased photosynthetic rate was caused by stomatal factors. The water use efficiency of P. chekiangensis was the highest under moderate drought conditions, and was lower by 29.6% and 46.4% under severe drought conditions than under control and moderate drought conditions, respectively. Under moderate drought conditions, the root radius of P. chekiangensis was significantly decreased, whereas the superoxidase dismutase (SOD), Peroxidase (POD), and Catalase (CAT) did not significantly decrease, and the average CAT actually increased slightly. However, under severe drought conditions the production of these three protective enzymes significantly decreased, and as a result antioxidant enzymes could not effectively scavenge reactive oxygen species. Therefore, it can be concluded that P. chekiangensis has some drought resistance. Moderate drought does not affect the normal growth of P. chekiangensis. Therefore, in the actual afforestation process, moderate control of the soil water content can be applied to preserve P. chekiangensis under conditions of mixed-patch afforestation of different tree species.