Does high-intensity light pre-treatment improve drought response in Thymus zygis ssp. gracilis?

Global concern regarding climate change is prompting the development of strategies to improve the resistance of plants to abiotic stresses. Drought is one of the main threats that affect the productivity of rainfed crops, such as T. zygis ssp. gracilis. Plants under stressful conditions may generate a "memory" that allows them to cope more effectively with future stress. Thus, the objective of this study was to determine whether the pre-treatment of thyme with high -intensity light -emitting diode light (light priming) could enhance its physiological response and activation of its antioxidant defense system to subsequent severe drought. To that end, physiological parameters including relative water content, and proline and abscisic acid levels, photosynthetic pigment and tocochromanols content, phenolic profiles, antioxidant capacity, and lipid peroxidation were quantified using 1600 clones from 20 ecotypes. Results confirmed the negative effect of drought on overall plant status, but also showed a positive effect of light priming, this improved the antioxidant system response in around of 70 % of ecotypes of red thyme. Specifically, light pre-treatment was associated with smaller reduction in content of photosynthetic pigments and tocochromanols, higher caffeic acid dimethyl ether content, and reduced lipid peroxidation in response to drought. Light priming may generate a "memory" that helps thyme overcome subsequent oxidative stress.