Leaf gas exchange characteristics differ among Sonoran Desert riparian tree species
Leaf gas exchange characteristics differ among Sonoran Desert riparian tree species
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DOI：
10.1093/treephys/21.4.233
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发表时间：
2001-03-01
期刊：
影响因子：
4
通讯作者：
Hart, SC
中科院分区：
文献类型：
--
作者：
Horton, JL;Kolb, T;Hart, SC
本文研究了两种本地索诺兰沙漠河岸树种弗里蒙特棉白杨叶杨（Populus fremontii S.）Wats.）和古丁杨柳（Salix gooddingii Ball.）相关物种）。在两个不同气候的地点进行了两年多的测量。由于多元线性回归模型解释的气孔导度（g（S））的变化小于29%，净光合速率（Pn）的变化小于48%的所有物种，我们使用边界线分析比较物种之间的气体交换反应。所有物种的气体交换率都很高。P-n和g（S）之间的双曲线关系表明，在高g（S）下，g（S）的初始降低并不抑制P-n。棉白杨和杨柳的g（S）的减少发生在Psi（md）值等于或低于先前报道的木质部空化阈值（分别为-1.6和-1.4 MPa）时，表明气孔对水分损失的严格调节和狭窄的空化安全裕度。相比之下，盐柏的g（S）减少发生在Psi md值远高于空化阈值（-7.0 MPa）时，但Psi（md）值远低于棉白杨和杨柳，表明盐柏的空化安全裕度更宽，对水分损失的调节更不严格。高VPD对杨柳叶片气体交换的影响小于棉白杨。相比之下，杨柳有一个较小的负PSI（PD）阈值气孔关闭比棉白杨。与棉白杨和杨柳相比，盐杉叶片气体交换对高VPD和低Psi（pd）的耐受性更强。这些生理特性的盐雪松解释了其广泛的成功，作为一个入侵者的河岸生态系统包含本地弗里蒙特棉白杨和古丁杨柳在索诺兰沙漠。
We investigated leaf gas exchange responses to lear temperature, leaf-to-air vapor pressure deficit (VPD), and predawn and midday shoot water potential (Psi (pd) and Psi (md), respectively) of two native Sonoran Desert riparian tree species, Fremont cottonwood (Populus fremontii S. Wats.) and Goodding willow (Salix gooddingii Ball), and one exotic riparian tree species, saltcedar (Tamarix chinensis Lour. and related species). Measurements were made at two sites over 2 years that differed climatically. Because multiple linear regression models explained less than 29% of the variation in stomatal conductance (g(S)) and less than 48% of the variation in net photosynthetic rate (P-n) of all species, we used boundary-line analysis to compare gas exchange responses among species. Gas exchange rates were high in all species. The hyperbolic relationship between P-n and g(S) suggested that initial reductions in g(S) at high g(S) did not inhibit P-n. Reductions in g(S) of cottonwood and willow occurred at Psi (md) values at or below previously reported xylem cavitation thresholds (-1.6 and -1.4 MPa, respectively), indicating tight stomatal regulation of water loss and a narrow cavitation safety margin. In contrast, reductions in g(S) of saltcedar occurred at Psi md values well above the cavitation threshold (-7.0 MPa), but at much lower Psi (md) values than in cottonwood and willow, suggesting a wider cavitation safety margin and less tight regulation of water loss in saltcedar. High VPD had a smaller effect on leaf gas exchange in willow than in cottonwood. In contrast, willow had a less negative Psi (pd) threshold for stomatal closure than cottonwood. Compared with cottonwood and willow, leaf gas exchange of saltcedar was more tolerant of high VPD and low Psi (pd). These physiological characteristics of saltcedar explain its widespread success as an invader of riparian ecosystems containing native Fremont cottonwood and Goodding willow in the Sonoran Desert.