A new measurement technique reveals rapid post-illumination changes in the carbon isotope composition of leaf-respired CO2
A new measurement technique reveals rapid post-illumination changes in the carbon isotope composition of leaf-respired CO2
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DOI：
10.1111/j.1365-3040.2007.01634.x
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发表时间：
2007-04-01
影响因子：
7.3
通讯作者：
Hanson, David T.
中科院分区：
文献类型：
--
作者：
Barbour, Margaret M.;McDowell, Nate G.;Hanson, David T.
我们描述了一个与可调谐二极管激光（TDL）光谱系统耦合的开放式叶片气体交换系统，该系统可以每3分钟测量一次叶片呼吸CO2通量及其相关的碳同位素组成（δ C-13(Rl)）。δ C-13（Rl）的测量精度可与传统质谱技术相媲美。经过24-48小时的长时间黑暗后，蓖麻（Ricinus communis L.）叶片的δ C-13（Rl）倾向于与CO2产生量与O-2消耗量[呼吸商（RQ）]之比呈正相关，支持现有模型。此外，在暗期开始后1-8小时内，呼吸基质和呼吸CO2之间的表观分异与先前的观测结果相似。在随后的试验中，在可变水分条件下种植红豆植物，以提供δ C-13范围内的近期固定碳水化合物。在黑暗期开始前暴露在高光照下的叶片中，在植物从光照环境移到黑暗环境后的前10-15分钟内，叶片呼吸的二氧化碳含量比韧皮部汁液糖含量高出千分之十一。然后在黑暗中30-60分钟后，呼吸二氧化碳中的C-13富集迅速下降到韧皮部汁液的3-7‰。如果在黑暗期开始之前光照水平较低，则不会观察到这种强烈的富集。RQ的测量证实，在光照后的前60分钟内，碳水化合物可能是植物的呼吸底物（RQ > 0.8）。高亮度到暗转换后的强C-13富集与高呼吸速率相吻合，表明所谓的光增强暗呼吸（LEDR）是由富含C-13的代谢物提供的。
We describ an open leaf gas exchange system coupled to a tunable diode laser (TDL) spectroscopy system enabling measurement of the leaf respiratory CO2 flux and its associated carbon isotope composition (delta C-13(Rl)) every 3 min. The precision of delta C-13(Rl) measurement is comparable to that of traditional mass spectrometry techniques. delta C-13(Rl) from castor bean (Ricinus communis L.) leaves tended to be positively related to the ratio of CO2 produced to O-2 consumed [respiratory quotient (RQ)] after 24-48 h of prolonged darkness, in support of existing models. Further, the apparent fractionation between respiratory substrates and respired CO2 within 1-8 h after the start of the dark period was similar to previous observations. In subsequent experiments, R. communis plants were grown under variable water availability to provide a range in delta C-13 of recently fixed carbohydrate. In leaves exposed to high light levels prior to the start of the dark period, CO2 respired by leaves was up to 11 parts per thousand more enriched than phloem sap sugars within the first 10-15 min after plants had been moved from the light into the dark. The C-13 enrichment in respired CO2 then decreased rapidly to within 3-7 parts per thousand of phloem sap after 30-60 min in the dark. This strong enrichment was not observed if light levels were low prior to the start of the dark period. Measurements of RQ confirmed that carbohydrates were the likely respiratory substrate for plants (RQ > 0.8) within the first 60 min after illumination. The strong C-13 enrichment that followed a high light-to-dark transition coincided with high respiration rates, suggesting that so-called light-enhanced dark respiration (LEDR) is fed by C-13-enriched metabolites.