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Temporal separation between CO 2 assimilation and growth? Experimental and theoretical evidence from the desiccation‐tolerant moss S yntrichia ruralis
Author(s) -
Royles Jessica,
Ogée Jérôme,
Wingate Lisa,
Hodgson Dominic A.,
Convey Peter,
Griffiths Howard
Publication year - 2013
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12114
Subject(s) - moss , desiccation , desiccation tolerance , stable isotope ratio , botany , cellulose , chemistry , assimilation (phonology) , environmental chemistry , photosynthesis , biology , biochemistry , physics , linguistics , philosophy , quantum mechanics
Summary The extent of an external water layer around moss tissue influences CO 2 assimilation. Experiments on the desiccation‐tolerant moss S yntrichia 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.