Comparative Effects of Light and Water Stresses on Antioxidant Enzymes Activity of Three Ecotypes of Jatropha curcas Seedlings

Jatropha curcas is a Euphorbiaceae whose seed lipids attract biofuel industry attention. However, the effects of environmental stressors inducing resistance mechanisms and affecting the seed yield of the plant are very little investigated. In this study, we evaluated the effect of water stress and sunlight luminosity on the antioxidant enzymes activities of Jatropha curcas. Seeds of three Jatropha curcas ecotypes coming from Burkina Faso were sown in reduced sunlight luminosity condition in the greenhouse. A 20 day water stress and/or 20 day direct sunlight stress was applied to 33 weeks old plants. Control plants grew in the greenhouse under a reduced sunlight quantity and received one liter water daily. The activities of leaf antioxidant enzymes, catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were measured using a spectrophotometer. The results showed that plants of Sahelian zone containing the greatest proline content had the highest enzymatic activity thereby indicating a better adaptation of the sahelian ecotype of J. curcas to water deficit and direct sunlight luminosity. The effect of water stress on enzymatic activities was more pronounced than the effect of direct sunlight luminosity. Our results suggest that the mechanisms modulating the enzymatic activity of young plants of J. curcas controlled by water deficit, such as inhibition of photosynthesis and photorespiration reinforcing, were earlier set up.