Effects of drought stress on the antioxidant systems in three species of Diospyros L

Drought stress is a limiting factor for plant cultivation in many areas of China and persimmon has good capacity to withstand water shortage. Three species of Diospyros (three accession of Diospyros lotus, referred to as accession No. 824, 846, and 847; one accession of Diospyros kaki var. sylvestris referred to as 869; and one accession of Diospyros virginiana referred to as 844) were chosen for drought stress analysis. We withheld water from healthy two-year-old potted seedlings for 20 days, and compared the effects of water stress on malondialdehyde (MDA), superoxide free radical (O₂ .⁻), hydrogen peroxide (H₂O₂), antioxidative enzyme, glutathione (GSH), and ascorbic acid (AsA) levels in the leaves of the three species. In the treatment group, water stress increased the membrane lipid peroxidation in the three species, but a more significant increase was observed in the D. kaki var. sylvestris 869 than in the D. virginiana 844. Moreover, accumulation of O₂ .⁻ and H₂O₂ was faster in weakly drought-resistant hybrids than in the highly drought- resistant hybrids. Though the activities of antioxidant enzymes and antioxidant contents were increased in the three species under drought stress, the activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase were stimulated to a greater extent in D. virginiana 844 than in D. lotus and D. kaki var. sylvestris 869. In addition, the GSH, AsA, and relative water contents were increased significantly in D. virginiana 844, but not in D. kaki var. sylvestris 869. In the control group, no significant changes in lipid peroxidation and relevant antioxidant parameters were detected among the three species. These results indicated that changes of MDA, O₂ .⁻, and H₂O₂ content, antioxidative enzyme activities, and GSH and AsA concentrations were correlated to drought resistance in the different species. D. virginiana 844 had a higher antioxidation capacity in response to drought than the other two species.