title: Photosynthesis is improved by exogenous calcium in heat-stressed tobacco plants.
abstract: Effects of exogenous calcium chloride (CaCl(2)) (20 mM) on photosynthetic gas exchange, photosystem II photochemistry, and the activities of antioxidant enzymes in tobacco plants under high temperature stress (43°C for 2 h) were investigated. Heat stress resulted in a decrease in net photosynthetic rate (P(n)), stomatal conductance as well as the apparent quantum yield (AQY) and carboxylation efficiency (CE) of photosynthesis. Heat stress also caused a decrease of the maximal photochemical efficiency of primary photochemistry (F(v)/F(m)). On the other hand, CaCl(2) application improved P(n), AQY, and CE as well as F(v)/F(m) under high temperature stress. Heat stress reduced the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), whereas the activities of these enzymes either decreased less or increased in plants pretreated with CaCl(2); glutathione reductase (GR) activity increased under high temperature, and it increased more in plants pretreated with CaCl(2). There was an obvious accumulation of H(2)O(2) and O(2)(-) under high temperature, but CaCl(2) application decreased the contents of H(2)O(2) and O(2)(-) under heat stress conditions. Heat stress induced the level of heat shock protein 70 (HSP70), while CaCl(2) pretreatment enhanced it. These results suggested that photosynthesis was improved by CaCl(2) application in heat-stressed plants and such an improvement was associated with an improvement in stomatal conductance and the thermostability of oxygen-evolving complex (OEC), which might be due to less accumulation of reactive oxygen species.
authors.affiliation: College of Life Science, State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Tan
authors.forename: Qing wei
authors.initials: Qw
authors.lastname: Meng
authors.forename: Marian
authors.initials: M
authors.lastname: Brestic
authors.forename: Katarina
authors.initials: K
authors.lastname: Olsovska
authors.forename: Xinghong
authors.initials: X
authors.lastname: Yang
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D017610:Calcium Compounds / Q000032:analysis / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D002704:Chlorates / Q000032:analysis / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D006358:Hot Temperature; D015227:Lipid Peroxidation / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects; D018526:Plant Transpiration / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological / Q000502:physiology*; D014026:Nicotiana / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*
chemical_list: D000975:Antioxidants; D017610:Calcium Compounds; D002704:Chlorates; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D002734:Chlorophyll; D002245:Carbon Dioxide; C091366:calcium chlorate; D017301:Ca(2+) Mg(2+)-ATPase