title: Temporal separation between CO2 assimilation and growth? Experimental and theoretical evidence from the desiccation-tolerant moss Syntrichia ruralis.
abstract: The extent of an external water layer around moss tissue influences CO(2) assimilation. Experiments on the desiccation-tolerant moss Syntrichia ruralis assessed the real-time dependence of the carbon and oxygen isotopic compositions of CO(2) and H(2)O in terms of moss water status and integrated isotope signals in cellulose. As external (capillary) water, and then mesophyll water, evaporated from moss tissue, assimilation rate, relative water content and the stable isotope composition of tissue water (δ(18)O(TW)), and the CO(2) and H(2)O fluxes, were analysed. After drying, carbon (δ(13)C(C)) and oxygen (δ(18)O(C)) cellulose compositions were determined. During desiccation, assimilation and (13)CO(2) discrimination increased to a maximum and then declined; δ(18)O(TW) increased progressively by 8‰, indicative of evaporative isotopic enrichment. Experimental and meteorological data were combined to predict tissue hydration dynamics over one growing season. Nonsteady-state model predictions of δ(18)O(TW) were consistent with instantaneous measurements. δ(13)C(C) values suggest that net assimilation occurs at 25% of maximum relative water content, while δ(18)O(C) data suggests that cellulose is synthesized during much higher relative water content conditions. This implies that carbon assimilation and cellulose synthesis (growth) may be temporally separated, with carbon reserves possibly contributing to desiccation tolerance and resumption of metabolism upon rehydration.
authors: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.|British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
authors: Jessica
authors: J
authors: Royles
authors: INRA, UR1263 EPHYSE, 71 Avenue Edouard Bourleaux, 33140, Villenave d'Ornon, France.
authors: Jérôme
authors: J
authors: Ogée
authors: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.|INRA, UR1263 EPHYSE, 71 Avenue Edouard Bourleaux, 33140, Villenave d'Ornon, France.
authors: Lisa
authors: L
authors: Wingate
authors: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
authors: Dominic A
authors: DA
authors: Hodgson
authors: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
authors: Peter
authors: P
authors: Convey
authors: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
authors: Howard
authors: H
authors: Griffiths
mesh_terms: D019068:Bryopsida / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000737:chemistry / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D014867:Water; D002245:Carbon Dioxide; D002482:Cellulose