Exogenous curcumin alleviates salt stress in lavender plants: a physiological and biochemical investigation

This work aimed to study the responses of Lavandula angustifolia (subspecies officinalis and angustifolia) to salt stress and curcumin (Cur). Salt stress was imposed by NaCl at different concentrations (0, 100, and 200 mM) with or without Cur (100 mg/L). Salt stress significantly inhibited growth in both subspecies (subsp.). However, subsp. officinalis was more NaCl sensitive and attained lower biomass under salt stress than subsp. angustifolia. Proline accumulation and reduction of chlorophylls were detected in both subsp. exposed to salt stress. An increment in malondialdehyde (MDA) content in stressed plants confirmed that salt stress led to oxidative damage in both subspecies. Exogenous application of Cur clearly improved growth in both subsp. under saline conditions, and this improvement was more obvious in subsp. angustifolia. Reduction in MDA content by Cur was observed in subsp. angustifolia at all the salinity levels. Amelioration of growth under salt stress by Cur can be explained by induction in chlorophylls, proteins and flavonols content in subsp. angustifolia and by induction in activities of superoxide dismutase (SOD), peroxidase (POX) and polyphenol oxidase (PPO), and content of total phenolics, flavonols and anthocyanins in subsp. officinalis. Overall, Cur regulated physiological and biochemical processes in lavender plants and aided to salt tolerance.