Half of the 18 O enrichment of leaf sucrose is conserved in leaf cellulose of a C 3 grass across atmospheric humidity and CO 2 levels

• Published in: Plant, cell and environment Vol. 47; no. 6; pp. 2274 - 2287
• Main Authors: Cabrera, Juan C Baca, Hirl, Regina T, Schäufele, Rudi, Zhu, Jianjun, Liu, Hai Tao, Gong, Xiao Ying, Ogée, Jérôme, Schnyder, Hans
• Format: Journal Article
• Language: English
• Published: United States Wiley 15.03.2024
• Subjects: Environmental Sciences; atmospheric CO2 concentration; relative humidity of air; 18O in leaf water; sucrose and cellulose; Lolium perenne (perennial ryegrass); Barbour-Farquhar model of 18O-enrichment in cellulose
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.14881

The O enrichment (Δ O) of cellulose (Δ O ) is recognized as a unique archive of past climate and plant function. However, there is still uncertainty regarding the proportion of oxygen in cellulose (p ) that exchanges post-photosynthetically with medium water of cellulose synthesis. Particularly, recent research with C grasses demonstrated that the Δ O of leaf sucrose (Δ O , the parent substrate for cellulose synthesis) can be much higher than predicted from daytime Δ O of leaf water (Δ O ), which could alter conclusions on photosynthetic versus post-photosynthetic effects on Δ O via p . Here, we assessed p in leaves of perennial ryegrass (Lolium perenne) grown at different atmospheric relative humidity (RH) and CO levels, by determinations of Δ O in leaves, Δ O (the Δ O of water in the leaf growth-and-differentiation zone) and both Δ O and Δ O (adjusted for ε , the biosynthetic fractionation between water and carbohydrates) as alternative proxies for the substrate for cellulose synthesis. Δ O was always close to irrigation water, and p was similar (0.53 ± 0.02 SE) across environments when determinations were based on Δ O . Conversely, p was erroneously and variably underestimated (range 0.02-0.44) when based on Δ O . The photosynthetic signal fraction in Δ O is much more constant than hitherto assumed, encouraging leaf physiological reconstructions.