Effect of Precipitation Exclusion on Physiological Characteristics of Fine Roots of Cunninghamia lanceolata Saplings

Abstract:

In order to reveal the response mechanism of Cunninghamia lanceolata to drought in subtropical region, the physiological characteristics of fine roots under precipitation exclusion were studied at the National Field Scientific Observation and Research Station of Forest Ecosystem in Sanming, Fujian. The results showed that soil moisture under precipitation exclusion decreased significantly (P < 0.05) compared with the control, but the contents of superoxide anion radical and malondialdehyde in fine roots had not significant differences (P > 0.05), indicating that the fine roots of Chinese fir maintained a low level of membrane lipid oxidation damage. The contents of proline, glutathione (GSH) and hydrogen peroxide (H₂O₂) increased significantly compared with the control (P < 0.05), indicating that Chinese fir was subjected to some degree of drought stress and self-regulation. GSH content significantly increased to some extent due to the accumulation of H₂O₂ caused by long-term precipitation exclusion, and there was a significant positive correlation between H₂O₂ and GSH (P < 0.01). Compared with the control, precipitation exclusion decreased the contents of endogenous hormones, such as cytokinin and indoleacetic acid, but they had not significantly correlated with the growth regulation of Chinese fir. In addition, the activity of superoxide dismutase under precipitation exclusion decreased by 21.5% (P < 0.05), and peroxidase activity increased by 16.7% (P < 0.05). However, the effect of antioxidant enzyme system on water deficit adaptation in fine roots of Chinese fir was weak. Therefore, Chinese fir could effectively adapt to the significant decrease of soil moisture under 50% precipitation exclusion through comprehensive regulation of non-enzymatic substances such as osmotic substances and endogenous hormones in fine roots.