The 18O‐signal transfer from water vapour to leaf water and assimilates varies among plant species and growth forms. (3rd December 2019) - Lehmann, Marco M.
Abstract: The 18 O signature of atmospheric water vapour (δ 18 OV ) is known to be transferred via leaf water to assimilates. It remains, however, unclear how the 18 O‐signal transfer differs among plant species and growth forms. We performed a 9‐hr greenhouse fog experiment (relative humidity ≥ 98%) with 18 O‐depleted water vapour (−106.7‰) on 140 plant species of eight different growth forms during daytime. We quantified the 18 O‐signal transfer by calculating the mean residence time of O in leaf water (MRTLW ) and sugars (MRTSugars ) and related it to leaf traits and physiological drivers. MRTLW increased with leaf succulence and thickness, varying between 1.4 and 10.8 hr. MRTSugars was shorter in C3 and C4 plants than in crassulacean acid metabolism (CAM) plants and highly variable among species and growth forms; MRTSugars was shortest for grasses and aquatic plants, intermediate for broadleaf trees, shrubs, and herbs, and longest for conifers, epiphytes, and succulents. Sucrose was more sensitive to δ 18 OV variations than other assimilates. Our comprehensive study shows that plant species and growth forms vary strongly in their sensitivity to δ 18 OV variations, which is important for the interpretation of δ 18 O values in plant organic material and compounds and thus for the reconstruction of climatic conditions and plant functional responses. Abstract : Our multispecies fog study revealed that the oxygen isotope signal transfer from water vapour to leaf water and assimilates varies substantially among plant species and growth forms. Our results help to improve the interpretation of the oxygen isotopic composition of water and organics in plants.