Physiological responses of lavender (Lavandula angustifolia Mill.) towater deficit and recovery

Lavender (Lavandula angustifolia Mill.) plants were subjected to repeated water depletions and rehydration in order to evaluate the physiological responses to water deficit. The first cycle of water deprivation (WD) was induced by withholding water after sufficient irrigation; plants and soil samples were harvested 3 and 7 days after water deprivation (3 DAW and 7 DAW, respectively). The other half of the water-deprived plants were sufficiently re-watered once, and plants and soil samples were collected 3 and 10 days after re-watering (3 DAR and 10 DAR, respectively). WD produced strong decreases in leaf hydration and remarkable increases of H2O2 contents, and these changes were recovered after irrigation. Leaf hydration and hydrogen peroxide (H2O2) contents were linearly correlated to soil water contents. Abundance of δ13C gradually increased during the experiment, indicating stomatal closure. Shoot/root ratios decreased in response to WD, particularly during the second cycle of WD. Generally, total carbon (C)and total nitrogen (N)contents decreased along the experiment, whereas, total soluble sugar contents and C/N ratios kept unchanged. Total amino acid (TAA) content dramatically accumulated at the expense of soluble protein upon WD and both nitrogen fractions fully recovered after irrigation. Compared to glutathione (GSH) that slightly increased in response to WD, ascorbate contents and dehydroascorbate (DHA) reductase activities were significantly impaired by WD, but resumed after re-watering. WD and re-watering had less pronounced effects on DHA contents and GSH reductase activities. In conclusion, lavender plants responded strongly to water deficit and the physiological alterations largely recovered to previous levels after irrigation, with the exception of total C and total N contents. Thus, episodic drought events may impact growth and productivity even in plants with high resilience.