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The 18 O‐signal transfer from water vapour to leaf water and assimilates varies among plant species and growth forms
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International audience. The 18 O signature of atmospheric water vapour (δ 18 O V ) 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 (MRT LW ) and sugars (MRT Sugars ) and related it to leaf traits and physiological drivers. MRT LW increased with leaf succulence and thickness, varying between 1.4 and 10.8 hr.
MRT Sugars was shorter in C 3 and C 4 plants than in crassulacean acid metabolism (CAM) plants and highly variable among species and growth forms; MRT Sugars 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 O V variations than other assimilates. Our comprehensive study shows that plant species and growth forms vary strongly in their sensitivity to δ 18 O V 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
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