Journal of Experimental Botany, Vol. 53, No. 376, pp. 1979-1987,
September 1, 2002
© 2002 Oxford University Press
Effects of low chronic doses of ionizing radiation on antioxidant enzymes and G6PDH activities in Stipa capillata (Poaceae)
Received 13 November 2001; Accepted 13 May 2002
1 UMR-CNRS 6553 Ecobio, Equipe Evolution des Populations et des Espèces, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex, France
2 Decision Strategy Research Department, SCKCEN Boeretang, 200 B-2400 Mol, Belgium
3 To whom correspondence should be addressed. E-mail: misset{at}univ-rennes1.fr
Stipa capillata (Poaceae) seeds were harvested from a control area (displaying a 
dose rate of 0.23 µSv h–1) (C plants) and from two contaminated areas (5.4 and 25 µSv h–1) on the Semipalatinsk nuclear test site (SNTS) in Kazakhstan. The plants were grown for 124 d in a greenhouse under controlled conditions and exposed to three different treatments: (0) control; (E) external irradiation delivered by a sealed 137Cs source with a dose rate of 66 µSv h–1; (E+I) E treatment combined with internal ß irradiation due to contamination by 134Cs and 85Sr via root uptake from the soil. The root uptake led to a contamination of 100 Bq g–1 for 85Sr and 5 Bq g–1 for 134Cs (of plant dry weight) as measured at harvest. The activity of SOD, APX, GR, POD, CAT, G6PDH, and MDHAR enzymes was measured in leaves. Under (0) treatment, all enzymes showed similar activities, except POD, which had higher activity in plants originating from contaminated areas. Treatment (E) induced an enhancement of POD, CAT, GR, SOD, and G6PDH activities in plants originating from contaminated areas. Only control plants showed any stimulation of APX activity. Treatment (E+I) had no significant effect on APX, GR, CAT, and POD activities, but MDHAR activity was significantly reduced while SOD and G6PDH activities were significantly increased. The increase occurred in plants from all origins for SOD, with a greater magnitude as a function of their origin, and it occurred only in plants from the more contaminated populations for G6PDH. This suggests that exposure to a low dose rate of ionizing radiation for almost a half century in the original environment of Stipa has led to natural selection of the most adapted genotypes characterized by an efficient induction of anti-oxidant enzyme activities, especially SOD and G6PDH, involved in plant protection against reactive oxygen species.
Key words: Key words: Antioxidant enzymes, ionizing radiation, Poaceae.
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