Antioxidant Activity: A Strategy for Alleviating the Effects of Drought on Calendula officinalis L.

Aims: Effects of drought stress on pot marigold and plant’s antioxidant responses in confronting with water deficit was studied.

Study Design: The experiment was conducted according complete randomized block design (CRBD) with three replications. Drought stress with four levels (80, 60, 40 and 20% of the soil available water content) and plant type (medicinal and ornamental) were considered. Means were compared using LSD test. Correlation analysis was done using Pearson Correlation Coefficient.

Place and Duration of Study: Research greenhouse of faculty of agriculture, University of Birjand, Iran; Between December 2014 and June 2015.

Methodology: Enzymatic antioxidants activity and non-enzymatic antioxidants content along with MDA (malondialdehyde) content were determined spectrophotometric and flower yield was consisted of the oven dried flowers collected during the reproductive stage.

Results: MDA content increased with increasing drought intensity from 17.97 in well-watered to 28.67 mmol.gr-1 fresh weight in severe stress level. SOD and CAT activity primarily increased to 8.58 u.mg-1 protein and 4.48 ΔA240.mg-1 protein in moderate stress level respectively and then decreased afterwards. APX activity decreased from 2.37 in well-watered level to 1.31 ΔA290.mg-1 protein in severe stress level. Proline content increased accompanied by increasing drought, so that in the highest level (36.17 mg.gr-1 fresh weight) was up to fourfold compared with non-stressed control. However carotenoid content concurrently decreased from 4.50 to 3.30 mg.gr-1 fresh weight. With increasing drought, flower yield decreased with a certain rate, so the highest (0.52 g.plant-1) and lowest (0.21 g.plant-1) flower yield belonged to non-stressed and intensive drought stress, respectively. In addition, flower yield of medicinal type was approximately 24% higher than ornamental one.

Conclusion: Enzymatic antioxidant system of pot marigold confers a suitable ability to reduce adverse effects of drought-induced oxidative stress. However when the intensity of drought stress is high, this scavenging system fails to cope with higher levels of oxidative compounds.