Drought and salinity are amongst the most damaging environmental stressors that can affect a plant's life cycle, from germination to senescence. In the present study were analysed the responses to salinity and drought in greenhouse-controlled conditions of two varieties of Lavandula angustifolia . Three-month-old lavender seedlings were subjected to water deficit and salt stress (100, 200 and 300 mM NaCl) during a 30-day period. Complementing a previous analysis focused on stress tolerance mechanisms based on the regulation of ion transport and the synthesis of osmolytes, we have now evaluated the effects of the water deficit and salt treatments on the generation of secondary oxidative stress, by measuring malondialdehyde levels, and the activation of antioxidant systems, both non-enzymatic and enzymatic, determining total phenolic compounds and flavonoids contents and calculating superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase specific activities, respectively, in extracts of control and stressed plants. The results obtained confirm that both lavender varieties react in the same way to the applied stress treatments, activating the same antioxidant responses. However, some differences were observed when comparing the specific mechanisms triggered by each type of stress. Thus, the oxidative stress induced under drought conditions was counteracted by accumulation of phenolic compounds and flavonoids, without apparent involvement of antioxidant enzymes. Salt stress, on the other hand, in addition to an increase in flavonoid levels also induced superoxide dismutase and catalase activities. These antioxidant responses are likely to contribute to the relatively high tolerance (as compared to most crops) of lavender to drought and salinity.
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