Effects of Soil Microbes on Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Elsholtzia splendens under Copper Stress Condition
Abstract:To determine the effects of soil microbes on the photosynthetic and physiological responses as well as the chlorophyll fluorescence parameters of Elsholtzia splendens, four soil treatments were analyzed in this experiment: the addition of copper (copper stress); a soil microbes inoculation; addition of copper and soil microbes inoculation; and no additional copper or soil microbes inoculation (CK). The results showed that the net photosynthetic rates (Pn), relative chlorophyll content, and water use efficiency (WUE) of E.splendens inoculated with the soil microbes were higher than those in the CK, and the differences among the various treatments were significant. There was a significant impact on the minimal fluorescence (Fo) and maximal efficiency of PSⅡ photochemistry (Fv/Fm). In comparison with CK, the additional copper treatment reduced Pn and stomatal conductance (Gs), but the intercellular CO2 concentration (Ci) increased, which was mainly due to a non-stomatal limitation. The addition of copper was found to reduce the relative chlorophyll content, but the soil microbes inoculation could increase it, and the difference between the treatments was significant. Soil microbes inoculated plants had higher Fv/Fm and Fo under copper stress. The Pn, WUE, and Gs of E.splendens inoculated with the soil microbes increased markedly. It was suggested that soil microbes inoculation could alleviate copper stress on E.splendens plants by improving the relative chlorophyll content, photosynthesis, and chlorophyll fluorescence of leaves.