title: Elevated CO2 enhances photosynthetic efficiency, ion uptake and antioxidant activity of Gynura bicolor DC. grown in a porous-tube nutrient delivery system under simulated microgravity.
abstract: It is well known that plants can grow under space conditions, however, perturbations of many biological phenomena have been highlighted due to the effect of altered gravity and its possible interaction with other factors (e.g., CO2 , ion radiation, etc. Our aim was to test whether elevated CO2 could provide 'protection' to Gynura bicolor against the damaging effects of simulated microgravity (SM) on photosynthesis, ion uptake and antioxidant activity. As compared to G. bicolor grown in ambient CO2 with no SM (ACO2 ), growth and yield of the plants increased under elevated ambient CO2 with no SM (ECO2 ) and decreased under ACO2 +SM, whereas there was no significant effect on ECO2 +SM. Reductions in the content of Chl a, carotenoids and Chl a+b were 17.9%, 20.7% and 17.9% under ACO2 +SM, respectively, but under ECO2 there was a significant effect on all photosynthetic pigments except Chl b, compared to ACO2 . Photosynthesis was improved under ECO2 with SM and such an improvement was associated with improved water use efficiency and instantaneous carboxylation efficiency. Furthermore, SM caused a reduction in ion absorption rate, except for Ca(2+) , while ECO2 increased the uptake rate. Finally, the activity of SOD, POD and the content of MDA and H2 O2 were enhanced under SM treatments and were highest in ACO2 +SM. In contrast, T-AOC activity and GSH content significantly declined in ACO2 +SM compared to other treatments. These results suggest that ACO2 is not sufficient to counteract SM impact, but the increase is usually caused by improvement in CO2 nutrition in ECO2 +SM in comparison with ACO2 +SM.
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing, China.|Institute of Environmental Biology and Life Support Technology, Beihang University, Beijing, China.
authors.forename: M
authors.initials: M
authors.lastname: Wang
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing, China.|Institute of Environmental Biology and Life Support Technology, Beihang University, Beijing, China.
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing, China.|Institute of Environmental Biology and Life Support Technology, Beihang University, Beijing, China.
authors.forename: C
authors.initials: C
authors.lastname: Dong
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing, China.|Institute of Environmental Biology and Life Support Technology, Beihang University, Beijing, China.|International Joint Research Center of Aerospace Biotechnology & Medical Engineering, University, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Fu
authors.affiliation: School of Biological Science and Medical Engineering, Beihang University, Beijing, China.|Institute of Environmental Biology and Life Support Technology, Beihang University, Beijing, China.|International Joint Research Center of Aerospace Biotechnology & Medical Engineering, University, Beijing, China.
authors.forename: H
authors.initials: H
authors.lastname: Liu
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D019659:Asteraceae / Q000187:drug effects* / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism*; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000187:drug effects*; D018474:Weightlessness Simulation
chemical_list: D000975:Antioxidants; D002245:Carbon Dioxide; D007501:Iron
keywords: Antioxidant defence system; Gynura bicolor 
  DC; elevated CO2; ion uptake; photosynthetic efficiency; simulated microgravity