Résumés
Abstract
Exposure of Azolla plants to UV-B radiation for 6 h resulted in a decrease in biomass and relative growth rate (RGR), which coincided with an increase in doubling time (DT) as compared with the control. Also, the protein content decreased. On the other hand, hydrogen peroxyde (H2O2) and malondialdehyde (MDA) accumulated significantly in UV-treated Azolla plants. Conversely, the addition of selenium (Se) at 1 ppm resulted in a significant increase in biomass and protein content of untreated and UV-treated Azolla plants, and a significant reduction in both H2O2 and MDA. Moreover, the addition of Se to UV-treated and untreated Azolla plants resulted in a significant increase in total ascorbate and total glutathione (GSH) contents compared with the control and UV-stressed Azolla plants. Also, glutathione redox potential (GSH/TG) increased significantly in UV-treated Azolla plants in the presence of Se. There also was a significant increase (38%) in ascorbate peroxidase (APX) activity in UV-treated plants compared with the control. APX activity in the presence of Se did not change significantly compared with the control. Glutathione reductase (GR) activity increased significantly in UV-treated Azolla, while glutathione peroxidase (GSH-PX) activity did not. On the other hand, both GSH-PX and GR activity in untreated and UV-treated Azolla plants were significantly enhanced by the application of Se to the nutrient media at a concentration of 1 ppm. Therefore, we can conclude that Se protects Azolla plants from UV-B stress.
Keywords:
- ascorbate,
- Azolla caroliniana,
- glutathione,
- glutathione peroxidase,
- selenium,
- UV-B radiation
Résumé
L’exposition de plants d’Azolla au rayonnement UV-B pendant 6 h a provoqué une diminution de la biomasse et du taux de croissance relative (TCR), coïncidant avec une augmentation du temps de doublement (TD) comparativement au témoin. Aussi, le contenu en protéines a diminué. Par contre, le peroxyde d’oxygène (H2O2) et le malondialdéhyde (MDA) se sont accumulés de façon significative dans les plants d’Azolla traités par rayonnement UV. À l’inverse, l’ajout de 1 ppm de sélénium (Se) a provoqué une augmentation importante de la biomasse et du contenu en protéines des plants d’Azolla exposés ou non au rayonnement UV, ainsi qu’une réduction importante du H2O2 et du MDA. De plus, l’ajout de Se a provoqué une augmentation importante du contenu total d’ascorbate et de glutathion chez les plants d’Azolla exposés ou non au rayonnement UV comparativement au témoin et aux plants d’Azolla exposés au rayonnement UV en présence de Se. Aussi, le potentiel d’oxydoréduction de glutathion (NrH) a augmenté significativement chez les plants d’Azolla exposés au rayonnement UV en présence de Se. Il y a également eu une augmentation importante (38 %) de l’activité d’ascorbate peroxydase (APX) chez les plants exposés au rayonnement UV comparativement au témoin. L’activité APX en présence de Se n’a pas changé de façon significative comparativement au témoin. L’activité de glutathion réductase (GR) a augmenté significativement chez l’Azolla exposé au rayonnement UV, mais ce n’était pas le cas pour l’activité de glutathion peroxydase (GSH-PX). Toutefois, l’activité de GSH-PX et l’activité de GR dans les plants d’Azolla traités ou non par rayonnement UV ont été rehaussées de façon significative par l’application de Se aux milieux nutritifs à une concentration de 1 ppm. Ainsi, nous pouvons conclure que le Se protège les plants d’Azolla du stress relié au rayonnement UV-B.
Mots-clés :
- ascorbate,
- Azolla caroliniana,
- glutathion,
- glutathion peroxydase,
- rayonnement UV-B,
- sélénium
Parties annexes
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