Divergence in delta(13)C of dark respired CO(2) and bulk organic matter occurs during the transition between heterotrophy and autotrophy in Phaseolus vulgaris plants.
Divergence in delta(13)C of dark respired CO(2) and bulk organic matter occurs during the transition between heterotrophy and autotrophy in Phaseolus vulgaris plants.
复制标题
菜豆植物在异养和自养之间的转变过程中，暗呼吸CO(2) 和大量有机物的δ(13)C 发生了分歧。
作者：
Camille Bathellier;F. Badeck;P. Couzi;Sébastien Harscoët;Caroline Mauve;J. Ghashghaie
近年来发表的大量证据表明，植物中发生光合后分化，导致异养器官（与自养器官相比）中的c富集。然而，对植物发育过程中这些反应变化的机制知之甚少。研究了豆荚（Phaseolus vulgaris）不同器官有机质和呼吸CO(2)在个体发育早期的同位素特征，以确定同位素变化发生的发育阶段。代谢物的同位素分析和质量平衡计算有助于限制所涉及的代谢过程。在植物尺度上，表观呼吸分馏在异养期持续为正（c. 1 / 1000），在自养期变为负（降至-3.08 / 1000）。光合作用开始后，有机质和呼吸CO(2)的同位素特征在叶片和根系中（相反方向）分化，最初与干种子非常接近（-26.83 +/- 0.69 /千）。呼出的CO(2)在叶片中达到-20 /千，在根中变为（13）c耗尽，下降到-29 /千。由此可见，各器官之间的同位素差异是在幼苗从异养向自养过渡过程中代谢变化的结果。它们尤其与呼吸和呼吸分馏有关。
Substantial evidence has been published in recent years demonstrating that postphotosynthetic fractionations occur in plants, leading to (13)C-enrichment in heterotrophic (as compared with autotrophic) organs. However, less is known about the mechanism responsible for changes in these responses during plant development. The isotopic signature of both organic matter and respired CO(2) for different organs of French bean (Phaseolus vulgaris) was investigated during early ontogeny, in order to identify the developmental stage at which isotopic changes occur. Isotopic analyses of metabolites and mass balance calculations helped to constrain the metabolic processes involved. At the plant scale, apparent respiratory fractionation was constantly positive in the heterotrophic phase (c. 1 per thousand) and turned negative with autotrophy acquisition (down to -3.08 per thousand). Initially very close to that of the dry seed (-26.83 +/- 0.69 per thousand), isotopic signatures of organic matter and respired CO(2) diverged (in opposite directions) in leaves and roots after onset of photosynthesis. Respired CO(2) reached values up to -20 per thousand in leaves and became (13)C-depleted down to -29 per thousand in roots. It was concluded that isotopic differences between organs occurred subsequent to metabolic changes in the seedling during the transition from heterotrophy to autotrophy. They were especially related to respiration and respiratory fractionation.