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| Physiological Effects of Leaf-air Vapor Pressure Deficit and Stomatal Conductance on Transpiration Rate of Populus euphratica in the Middle and Lower Reaches of Tarim River |
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| DOI：10.16768/j.issn.1004-874X.2020.08.007 |
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| Abstract: |
| 【Objective】The transpiration rate mechanism of Populus euphratica during the fast growing period and the physiological regulation to adapt to arid climate environment were studied so as to provide experimental basis for the artificial regeneration of P. euphratica forest in the middle and lower reaches of the Tarim River.【Method】The portable photosynthesis instrument was used to measure the natural P. euphratica along the Tarim River in the extreme arid area in June to August of 2018. The measured data was used to study the correlation between transpiration rate （Tr） of P. euphratica and leaf-air vapor pressure deficit （VPDL） and stomatal conductance （Gs）.【Result】The diurnal variation of Tr and Gs of P. euphratica showed a single-peak curve during the observation period, and the peak occurrence time was different. In July, the trend of Tr and Gs showed a bimodal curve, and VPDL had a single-peak curve with a peak time at 16:00 The peak times of Tr and VPDL showed different degrees of hysteresis compared with the peak of Gs, with strong hysteresis. The occurrence of the bimodal curve was mainly affected by the non-stomatal limiting factors, which caused Tr and Gs to reach the first peak. After that, Tr and Gs decreased first and then rose and finally fell. All of Tr, VPDL and Gs of P. euphratica exhibited a quadratic curve model, indicating that leaf-air vapor pressure deficit and stomatal conductance were both important factors regulating the transpiration rate. During the observation period, P. euphratica was alternately affected by stomatal limitation and non-stomatal limitation. The period of each month affected by the stomatal and non-stomatal limitation was different, therefore, there were different physiological and ecological reflections on plants.【Conclusion】The response sensitivity of P. euphratica Tr to VPDL is higher than that of Gs in the middle and lower reaches of the Tarim River. Non-stomatal restriction is also an important mechanism to maintain water balance. |
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