title: Maintenance of C sinks sustains enhanced C assimilation during long-term exposure to elevated [CO2] in Mojave Desert shrubs.
abstract: 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)].
authors.affiliation: Fisiologia Vegetal y Agrobiologia, Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, Campus de Arrosadia, Mutilva Baja, Spain. iker.aranjuelo@gmail.com
authors.forename: Iker
authors.initials: I
authors.lastname: Aranjuelo
authors.forename: Allison L
authors.initials: AL
authors.lastname: Ebbets
authors.forename: R Dave
authors.initials: RD
authors.lastname: Evans
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
authors.forename: Salvador
authors.initials: S
authors.lastname: Nogués
authors.forename: Natasja
authors.initials: N
authors.lastname: van Gestel
authors.forename: Paxton
authors.initials: P
authors.lastname: Payton
authors.forename: Volker
authors.initials: V
authors.lastname: Ebbert
authors.forename: Williams W
authors.initials: WW
authors.lastname: Adams
authors.forename: Robert S
authors.initials: RS
authors.lastname: Nowak
authors.forename: Stanley D
authors.initials: SD
authors.lastname: Smith
mesh_terms: D031164:Ambrosia / Q000502:physiology*; D000704:Analysis of Variance; D002244:Carbon / Q000032:analysis / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D004777:Environment; D032442:Larrea / Q000502:physiology*; D015999:Multivariate Analysis; D009505:Nevada; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D012621:Seasons
chemical_list: D002245:Carbon Dioxide; D002244:Carbon