title: Effects of 60-day NO2 fumigation on growth, oxidative stress and antioxidative response in Cinnamomum camphora seedlings.
abstract: OBJECTIVE
  To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide (NO(2)) fumigation.
  
  
  METHODS
  Measurements were made up of the growth, chlorophyll content, chlorophyll fluorescence, antioxidant system and lipid peroxidation of one-year-old C. camphora seedlings exposed to NO(2) (0.1, 0.5, and 4 microl/L) fumigation in open top chambers over a period of 60 d.
  
  
  RESULTS
  After the first 30 d, 0.5 and 4.0 microl/L NO(2) showed insignificant effects on the growth of C. camphora seedlings. However, exposure to 0.5 and 4.0 microl/L NO(2) for 15 d significantly reduced their chlorophyll content (P<0.05), enhanced their malondialdehyde (MDA) content and superoxide dismutase (SOD) activity (P<0.05), and also significantly reduced the maximal quantum yield of PSII in the dark [the ratio of variable fluorescence to maximal fluorescence (F(v)/F(m))] (P<0.05). In the latter 30 d, 0.5 microl/L NO(2) showed a positive effect on the vitality of the seedlings, which was reflected by a recovery in the ratio of F(v)/F(m) and chlorophyll content, and obviously enhanced growth, SOD activity, ascorbate (AsA) content and glutathione reductase (GR) activity (P<0.05); 4.0 microl/L NO(2) then showed a negative effect, indicated by significant reductions in chlorophyll content and the ratio of F(v)/F(m), and inhibited growth (P<0.05).
  
  
  CONCLUSIONS
  The results suggest adaptation of C. camphora seedlings to 60-d exposure to 0.1 and 0.5 microl/L NO(2), but not to 60-d exposure to 4.0 microl/L NO(2). C. camphora seedlings may protect themselves from injury by strengthening their antioxidant system in response to NO(2)-induced oxidative stress.
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China.
authors.forename: Zhuo-mei
authors.initials: ZM
authors.lastname: Chen
authors.forename: Ying-xu
authors.initials: YX
authors.lastname: Chen
authors.forename: Guo-jian
authors.initials: GJ
authors.lastname: Du
authors.forename: Xi-lin
authors.initials: XL
authors.lastname: Wu
authors.forename: Feng
authors.initials: F
authors.lastname: Li
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D027423:Cinnamomum camphora / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D009569:Nitric Oxide / Q000008:administration & dosage*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*
chemical_list: D000975:Antioxidants; D009569:Nitric Oxide