Internal conductance to CO2 diffusion and C18OO discrimination in C3 leaves
Internal conductance to CO2 diffusion and C18OO discrimination in C3 leaves
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DOI：
10.1104/pp.123.1.201
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发表时间：
2000-05-01
期刊：
影响因子：
7.4
通讯作者：
Yakir, D
中科院分区：
文献类型：
--
作者：
Gillon, JS;Yakir, D
O-18在CO2中的区分源于富含O-18的水与叶绿体中的CO2之间的氧交换，这是一个由碳酸酐酶（CA）催化的过程。一部分O-18标记的CO2逃逸回大气，导致光合作用期间对（COO）-O-18的有效区分（Delta（18）O）。通过分析蒸腾水和CO_2-H_2O同位素平衡程度来限制叶绿体水的δ（18）O（δ（e（θ（eq）），通过测量CA活性（对于烟草、大豆和橡木，θ（eq）= 0.75-1.0），我们可以将测量的δ（18）O应用于连接到质谱仪的叶片比色皿中以导出CA活性的物理极限处的CO2浓度，即叶绿体表面（c（cs））。根据气孔间气体交换（c（i））、δ（18）O（c（cs））和Rubisco位点δ（13）C（c（c））的CO2下降顺序，将内部CO2导度（g（i））分为细胞壁（g（w））和叶绿体（g（ch））两部分。结果表明，g（ch）是可变的（0.42-1.13 mol m（-2）s（-1）），与CA活性成正比。我们认为，CA活性对CO2同化率的影响应该是重要的，主要是在低内部电导的植物。
O-18 discrimination in CO2 stems from the oxygen exchange between O-18-enriched water and CO2 in the chloroplast, a process catalyzed by carbonic anhydrase (CA). A proportion of this O-18-labeled CO2 escapes back to the atmosphere, resulting in an effective discrimination against (COO)-O-18 during photosynthesis (Delta(18)O). By constraining the delta(18)O of chloroplast water (delta(e)) by analysis of transpired water and the extent of CO2-H2O isotopic equilibrium (theta(eq)) by measurements of CA activity (theta(eq) = 0.75-1.0 for tobacco, soybean, and oak), we could apply measured Delta(18)O in a leaf cuvette attached to a mass spectrometer to derive the CO2 concentration at the physical limit of CA activity, i.e. the chloroplast surface (c(cs)). From the CO2 drawdown sequence between stomatal cavities from gas exchange (c(i)), from Delta(18)O (c(cs)), and at Rubisco sites from Delta(13)C (c(c)), the internal CO2 conductance (g(i)) was partitioned into cell wall (g(w)) and chloroplast (g(ch)) components. The results indicated that g(ch) is variable (0.42-1.13 mol m(-2) s(-1)) and proportional to CA activity. We suggest that the influence of CA activity on the CO2 assimilation rate should be important mainly in plants with low internal conductances.