Mitigation of drought stress in pot marigold (Calendula officinalis) plant by foliar application of methanol

To study the effects of methanol on some physiological and biochemical characteristics of pot marigold (Calendula officinalis L.) under drought stress, a factorial experiment was conducted based on a randomized complete block design with three replications under greenhouse conditions in 2017. Factors included the foliar application of methanol at four levels [0 (control), 20%, 30% and 40%] and four irrigation treatments (irrigation at 40, 60, 80 and 100% of field capacity). Increasing water deficit, significantly reduced chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, Fv/Fm and stomatal conductance, whereas 20 and 30% methanol application significantly improved these traits. Irrespective of 40% methanol application, the moderate and severe water deficit treatments led to the decrease of chlorophyll a, total chlorophyll, carotenoid and Fv/Fm. Also, water deficit showed a significant increase in soluble sugars content, proline accumulation and CAT, POD and PPO activity. Compared with the non-methanol treatment, the application of methanol increased the above- mentioned characteristics. The maximum values of these variables were obtained with the application of 40% methanol under severe water limitation conditions. It was indicated that the improvement of biomass due to methanol spraying was associated with the increase of antioxidant defense abilities and maintaining many physiological processes in the stressed plants.