Résumé
Effect of photoinhibition of sorghum leaves and isolated chloroplasts on chlorophyll fluorescence, peroxidation of thylakoid lipids and activity of antioxidant enzymes were studied. Photoinhibition of intact leaves and isolated chloroplasts decreased Fv/Fm ratio and qP, while qN increased. Photoinhibitory damage was more at 5 degrees C than at 30 degrees or 50 degrees C. Peroxidation of thylakoid lipids was 5 times greater when photoinhibited at 50 degrees C compared to control. Photoinhibition of chloroplasts under low oxygen condition or when supplemented with anti-oxidants (beta-carotene, ascorbate and GSH) resulted in significantly less damage to photosynthesis (Fv/Fm ratio) and peroxidation level. Photoinhibition also resulted in many fold increase in the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and decrease in catalase. Data presented here suggest that photoinhibition resulted in production of oxygen radicals and photoinhibition of chloroplasts in the presence of low oxygen level or when supplemented with antioxidants decreased the damage to Fv/Fm ratio and peroxidation level to a great extent since former prevented the formation of oxygen radicals and later could scavenge the oxygen radicals thus the protection. Increase activity of SOD and APX may also be to metabolise the oxygen radicals produced during photoinhibition treatment, thereby, protecting the seedlings against photooxidative damage.
Sujets)
Antioxydants/administration et posologie , Acide ascorbique/administration et posologie , Catalase/métabolisme , Chloroplastes/effets des médicaments et des substances chimiques , Piégeurs de radicaux libres/pharmacologie , Glutathion/administration et posologie , Lumière/effets indésirables , Peroxydation lipidique/effets des médicaments et des substances chimiques , Stress oxydatif/effets des médicaments et des substances chimiques , Peroxidases/métabolisme , Poaceae/enzymologie , Espèces réactives de l'oxygène/métabolisme , Plant/composition chimique , Superoxide dismutase/métabolisme , Bêtacarotène/administration et posologieRésumé
Pennisetum pedicellatum plants were inoculated with Glomus mosseae, G. aggregatum and Gigaspora margarita. There were both quantitative and qualitative changes in the protein pattern of inoculated plants. Gi. margarita induced increase in protein in the plants. Acid phosphatase, alkaline phosphatase, superoxide dismutase and chitinase activities were high at the beginning of infection, but declined as the infection advanced. Gi. margarita was an efficient fungus in enhancing enzyme activity and proteins in roots compared with G. mosseae and G. aggregatum. Protein profile revealed the presence of 12 peaks in mycorrhizal plants compared with 8 in nonmycorrhizal plants.