Evaluation of the physiological parameters in Lavandula latifolia Medik. under water deficit for preselection of elite drought-resistant plants

Lavandula latifolia Medik. is an aromatic-medicinal plant, native to the Mediterranean region, for which economic interest is mainly focused on the production of essential oil. In the Mediterranean area, the negative effects of climate change, with increasingly frequent extreme heatwaves and drought episodes, have led to the need to select plants with greater tolerance of such scenarios for the future development of this rainfed crop. In the current study, young plants of spike lavender were subjected to a first episode of water deprivation. Subsequently, clones from the surviving ecotypes (SL1 to SL8) were assigned randomly to two homogeneous groups. One group was irrigated to field capacity (as a control) and the other was subjected to water stress for two months. In the leaves of control and stressed plants, physiological parameters including relative water content (% RWC), hydric potential (psi WP), proline, and abscisic acid were measured. The plant antioxidant defense system was also explored, through analysis of non-enzymatic antioxidants (alpha-tocopherol, plastochromanol-8), lipid peroxidation (MDA), and photosynthetic pigments (chlorophylls a and b, and carotenoids). The polyphenolic profile was determined and its corresponding antioxidant activity was analyzed for the first time in the early growth stages of this species. Under the drought treatment, the values of the physiological parameters were similar in all ecotypes and changed as the dehydration advanced. However, the response of the antioxidant defense to drought was variable depending on the ecotype under study. As a general pattern, there was a reduction in the concentration of photosynthetic pigments. Although, no statistical differences were detected in alpha-tocopherol and PC-8, in most cases, the MDA values increased significantly after the drought episode. In the polyphenolic profile identified, p-coumaric acid glycoside and rosmarinic acid-3-O-glucoside were the major components quantified, salvianic acid and O-coumaric acid being described for the first time in this species. Regarding the response of these chemical components to water stress, the concentrations of most polyphenols decreased, with the exception of rosmarinic acid, whose concentration after the stress was higher in three of the eight ecotypes under study. This increment was reflected in a higher in vitro antioxidant capacity. These findings suggest that L. latifolia was affected by drought, even though it showed some strategies to counteract the negative effects of dehydration. The intraspecific variation in the response to dehydration can be considered a useful tool for the preselection of ecotypes with greater resistance to this stress.