隔离降水对杉木幼树细根生理特征的影响

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

摘要:

为揭示亚热带地区杉木(Cunninghamia lanceolata)对干旱的响应机制，在福建三明森林生态系统国家野外科学观测研究站，对隔离降水环境下杉木幼树细根生理特征进行研究。结果表明，隔离降水处理的土壤湿度显著下降(P < 0.05)，但杉木细根超氧阴离子自由基、丙二醛含量变化不显著(P > 0.05)，表明其细根保持着低水平的膜脂氧化损伤；脯氨酸和谷胱甘肽含量较对照显著增加(P < 0.05)，并且过氧化氢含量也显著增加(P < 0.05)，意味着杉木受到一定程度的干旱胁迫并且进行自我调节；长期降水隔离导致的过氧化氢积累一定程度上促使谷胱甘肽显著提高，二者呈极显著正相关(P < 0.01)；内源激素中细胞分裂素、吲哚乙酸含量显著下降，与杉木生长调控未表现出明显相关性；超氧化物歧化酶活性较对照显著下降21.5%，过氧化物酶活性较对照显著提高16.7%，但抗氧化酶系统对杉木细根的水分缺失适应调控无显著影响。因此，50%降水减少条件下杉木能通过其细根的渗透物质和内源激素等非酶促物质进行综合调节，以有效适应土壤湿度的显著降低。

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.