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Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO 2 ] in Mojave Desert shrubs
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During the first few years of elevated atmospheric [CO(2)] treatment at the Nevada Desert FACE Facility, photosynthetic downregulation was observed in desert shrubs grown under elevated [CO(2)], especially under relatively wet environmental conditions. Nonetheless, those plants maintained increased A (sat) (photosynthetic performance at saturating light and treatment [CO(2)]) under wet conditions, but to a much lesser extent under dry conditions. To determine if plants continued to downregulate during long-term exposure to elevated [CO(2)], responses of photosynthesis to elevated [CO(2)] were examined in two dominant Mojave Desert shrubs, the evergreen Larrea tridentata and the drought-deciduous Ambrosia dumosa, during the eighth full growing season of elevated [CO(2)] treatment at the NDFF. A comprehensive suite of physiological processes were collected. Furthermore, we used C labeling of air to assess carbon allocation and partitioning as measures of C sink activity. Results show that elevated [CO(2)] enhanced photosynthetic performance and plant water status in Larrea, especially during periods of environmental stress, but not in Ambrosia. δ(13)C analyses indicate that Larrea under elevated [CO(2)] allocated a greater proportion of newly assimilated C to C sinks than Ambrosia. Maintenance by Larrea of C sinks during the dry season partially explained the reduced [CO(2)] effect on leaf carbohydrate content during summer, which in turn lessened carbohydrate build-up and feedback inhibition of photosynthesis. δ(13)C results also showed that in a year when plant growth reached the highest rates in 5 years, 4% (Larrea) and 7% (Ambrosia) of C in newly emerging organs were remobilized from C that was assimilated and stored for at least 2 years prior to the current study. Thus, after 8 years of continuous exposure to elevated [CO(2)], both desert perennials maintained their photosynthetic capacities under elevated [CO(2)]. We conclude that C storage, remobilization, and partitioning influence the responsiveness of these desert shrubs during long-term exposure to elevated [CO(2)].
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ARANJUELO, Iker, EBBETS, Allison l., EVANS, R. dave, TISSUE, David t., NOGUÉS MESTRES, Salvador, VAN GESTEL, Natasja, PAYTON, Paxton, EBBERT, Volker, ADAMAS III, Williams w., NOWAK, Robert s., SMITH, Stanley d.. Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO 2 ] in Mojave Desert shrubs. _Oecologia_. 2011. Vol. 167, núm. 2, pàgs. 339-354. [consulta: 20 de gener de 2026]. ISSN: 0029-8549. [Disponible a: https://hdl.handle.net/2445/197768]