title: C3 photosynthesis in the desert plant Rhazya stricta is fully functional at high temperatures and light intensities.
abstract: The C3 plant Rhazya stricta is native to arid desert environment zones, where it experiences daily extremes of heat, light intensity (PAR) and high vapour pressure deficit (VPD). We measured the photosynthetic parameters in R. stricta in its native environment to assess the mechanisms that permit it to survive in these extreme conditions. Infrared gas exchange analysis examined diel changes in assimilation (A), stomatal conductance (gs ) and transpiration (E) on mature leaves of R. stricta. A/ci analysis was used to determine the effect of temperature on carboxylation capacity (Vc,max ) and the light- and CO2 -saturated rate of photosynthesis (Amax ). Combined chlorophyll fluorescence and gas exchange light response curve analysis at ambient and low oxygen showed that both carboxylation and oxygenation of Rubisco acted as the major sinks for the end products of electron transport. Physiological analysis in conjunction with gene expression analysis suggested that there are two isoforms of Rubisco activase which may provide an explanation for the ability of R. stricta to maintain Rubisco function at high temperatures. The potential to exploit this ability to cope with extreme temperatures is discussed in the context of future crop improvement.
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Tracy
authors.initials: T
authors.lastname: Lawson
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Davey
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Yates
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Bechtold
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Baeshen
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia.
authors.forename: Nabih
authors.initials: N
authors.lastname: Baeshen
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia.
authors.forename: Mohammed Z
authors.initials: MZ
authors.lastname: Mutwakil
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia.
authors.forename: Jamal
authors.initials: J
authors.lastname: Sabir
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Baker
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Mullineaux
mesh_terms: D029062:Apocynaceae / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology; D002940:Circadian Rhythm / Q000187:drug effects / Q000528:radiation effects; D003889:Desert Climate; D006358:Hot Temperature; D008027:Light; D010788:Photosynthesis / Q000528:radiation effects*; D010802:Phylogeny; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism; D055548:Vapor Pressure
chemical_list: D010940:Plant Proteins; C054765:rca protein, plant; D002245:Carbon Dioxide; D002244:Carbon
keywords: C3 photosynthesis; Rhazya stricta; Rubisco activase; heat stress; stomatal conductance; thermotolerance; transpiration