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Free keywords:
Cryptogams
delta O-18 discrimination
Isotope equilibration
Modelling
Vapour
Water exchange
BIOLOGICAL SOIL CRUSTS
LEAF WATER
(COO)-O-18 DISCRIMINATION
CARBONIC-ANHYDRASE
EVAPORATION
ENRICHMENT
EXCHANGE
PLANTS
VAPOR
CO2
Abstract:
The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition.
