Zhang Yong E, Yu Xin Xiao, Chen Li Hua, Jia Guo Dong, Zhao Na, Li Han Zhi, Chang Xiao Min
Ministry of Education Key Laboratory of Soil & Water Conservation and Desertification Combating, Beijing Forestry University, Beijing 100083, China.
Ying Yong Sheng Tai Xue Bao. 2017 Jul 18;28(7):2149-2154. doi: 10.13287/j.1001-9332.201707.020.
The determination of plant foliar water use efficiency will be of great value to improve our understanding about mechanism of plant water consumption and provide important basis of regional forest ecosystem management and maintenance, thus, laboratory controlled experiments were carried out to obtain Platycladus orientalis sapling foliar water use efficiency under five different soil water contents, including instantaneous water use efficiency (WUE) derived from gas exchange and short-term water use efficiency (WUE) caculated using carbon isotope model. The results showed that, controlled by stomatal conductance (g), foliar net photosynthesis rate (P) and transpiration rate (T) increased as soil water content increased, which both reached maximum va-lues at soil water content of 70%-80% field capacity (FC), while WUE reached a maximum of 7.26 mmol·m·s at the lowest soil water content (35%-45% FC). Both δC of water-soluble leaf and twig phloem material achieved maximum values at the lowest soil water content (35%-45% FC). Besides, δC values of leaf water-soluble compounds were significantly greater than that of phloem exudates, indicating that there was depletion in C in twig phloem compared with leaf water-soluble compounds and no obvious fractionation in the process of water-soluble material transportation from leaf to twig. Foliar WUE also reached a maximum of 7.26 mmol·m·s at the lowest soil water content (35%-45% FC). There was some difference between foliar WUE and WUE under the same condition, and the average difference was 0.52 mmol·m·s. The WUE had great space-time variability, by contrast, WUE was more representative. It was concluded that P. orientalis sapling adapted to drought condition by increasing water use efficiency and decreasing physiological activity.
植物叶片水分利用效率的测定对于增进我们对植物水分消耗机制的理解具有重要价值，并为区域森林生态系统的管理和维护提供重要依据。因此，开展了实验室控制实验，以获取五种不同土壤水分含量下侧柏幼树叶片的水分利用效率，包括通过气体交换得出的瞬时水分利用效率（WUE）以及使用碳同位素模型计算得出的短期水分利用效率（WUE）。结果表明，在气孔导度（g）的控制下，叶片净光合速率（P）和蒸腾速率（T）随着土壤水分含量的增加而升高，二者在土壤水分含量为田间持水量（FC）的70%-80%时均达到最大值，而WUE在最低土壤水分含量（35%-45% FC）时达到最大值7.26 mmol·m·s。叶片水溶性物质和小枝韧皮部物质的δC均在最低土壤水分含量（35%-45% FC）时达到最大值。此外，叶片水溶性化合物的δC值显著高于韧皮部渗出物的δC值，这表明与叶片水溶性化合物相比，小枝韧皮部中的碳存在亏缺，并且在水溶性物质从叶片运输到小枝的过程中没有明显的分馏现象。叶片WUE在最低土壤水分含量（35%-45% FC）时也达到最大值7.26 mmol·m·s。在相同条件下，叶片WUE与WUE之间存在一定差异，平均差异为0.52 mmol·m·s。WUE具有较大的时空变异性，相比之下，WUE更具代表性。研究得出结论，侧柏幼树通过提高水分利用效率和降低生理活性来适应干旱条件。
