Turnover time of the non-structural carbohydrate pool influences δ18O of leaf cellulose

Abstract

Certainty regarding the degree to which organic molecules exchange oxygen with local water during plant cellulose synthesis (pex) is necessary for cellulose oxygen isotope (δ18Ocell)-based applications in environmental and ecological studies. However, the currently accepted notion that pex is a constant of ca. 0.42 appears inconsistent with biochemical theory, which predicts that marked variation may be present in pex, in relation to variation in the turnover time (τ) of the carbohydrate pool available for cellulose synthesis. The above prediction was tested in the present study with the analysis of data collected from leaves of Ricinus communis grown in controlled environmental conditions that varied in light intensity and vapour pressure deficit. The results revealed the existence of considerable variation in both pex and τ across plants in the various growth environments. Moreover, despite uncertainties in estimates of the proportion of source water in the synthesis water (px) and of the biochemical fractionation factor (εo), our experiment yielded strong evidence that pex exhibits a significant, positive relationship with τ, consistent with biochemical theory. The observed variation in pex in association with τ has important implications for the interpretation of δ18Ocell data in environmental/ecological studies. Show more