SEASONAL-VARIATION IN THE CARBON ISOTOPIC COMPOSITION OF DESERT PLANTS
SEASONAL-VARIATION IN THE CARBON ISOTOPIC COMPOSITION OF DESERT PLANTS
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DOI：
10.2307/2389277
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发表时间：
1992-01-01
影响因子：
5.2
通讯作者：
COMSTOCK, JP
中科院分区：
文献类型：
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作者：
EHLERINGER, JR;PHILLIPS, SL;COMSTOCK, JP
1.碳同位素区分（DELTA）已被证明是一个有价值的长期用水效率的估计，因为这一参数是由细胞间的环境CO2水平，这反过来又关系到用水效率的比例的影响。本研究的目的是检查现场材料的DELTA值的变化以及DELTA的变化在多大程度上可以解释为水利用效率的变化。在线歧视观察与四个沙漠物种证实理论上预期的DELTA和细胞间的比例与环境CO2浓度之间的关系，一个先决条件，应用DELTA值的水利用效率。在亚利桑那州西部的两个生长季节的过程中，在15个沙漠物种的三角洲值的季节性变化进行了测量。出现了两大格局：在某些物种的叶片中，一年中的变化为千分之2-3，而在其他物种中，同位素组成的变化小于千分之1。当碳同位素分析应用于水利用效率外推，它已被假定，叶温度是相当的物种之间进行比较。这一假设的误差分析表明，叶温差和同位素组成的差异，必要区分水分利用效率的差异之间的近线性关系。当植物之间的叶温差小于或等于2.5摄氏度时，DELTA的千分之一差异足以正确和明确地对植物的水分利用效率进行排名，这表明在计算水分利用效率时，细胞间CO2的变化可以抵消植物之间蒸发梯度的可能差异。由于不同物种之间的叶DELTA值在给定的采样日期通常为千分之四，碳同位素歧视似乎是一个可行的方法，排名干旱土地植物之间的相对水分利用效率的差异。
1. Carbon isotope discrimination (DELTA) has been shown to be a valuable too for long-term estimates of water-use efficiency, because this parameter is influenced by the ratio of intercellular to ambient CO2 levels, which is in turn related to water-use efficiency. The objective of this study was to examine variation in DELTA-values of field materials and the extent to which changes in DELTA might be interpreted as changes in water-use efficiency.2. On-line discrimination observations with four desert species confirmed theoretically expected relationships between DELTA and the ratio of intercellular to ambient CO2 concentrations, a prerequisite to applying DELTA-values to water-use efficiency. Seasonal changes in DELTA-values were measured in 15 desert species over the course of two growing seasons in western Arizona.3. Two major patterns appeared: in leaves of some species there were 2-3 parts per thousand changes during the year, whereas in others the changes in isotopic composition were less than 1 parts per thousand.4. When carbon isotope analyses are applied to water-use efficiency extrapolations, it has been assumed that leaf temperatures are equivalent among the species being compared. An error analysis of this assumption indicated a near-linear relationship between leaf temperature differential and the difference in isotopic composition necessary to distinguish differences in water-use efficiency. When leaf temperature differentials between plants were less-than-or-equal-to 2.5-degrees-C, a 1 parts per thousand difference in DELTA was sufficient to rank plants correctly and unambiguously with respect to water-use efficiency, indicating the extent to which changes in intercellular CO2 can offset possible differences in the evaporative gradient among plants when calculating water-use efficiencies.5. As leaf DELTA-values among different species often range 4 parts per thousand on a given sampling date, carbon isotope discrimination appears to be a feasible approach for ranking relative water-use efficiency differences among arid-land plants.