Effect of Foliar Application of Proline on Morphological and Physiological Traits of Calendula officinalis L. under Drought Stress

Drought stress is one of the most important abiotic stresses that seriously reduces the production of ornamental plants such as pot marigold. Proline is one of the active amino acids in the osmotic regulation phenomenon and it has an effective role in reducing cell damage and improving drought tolerance. A pot experiment as factorial arrangement in a completely randomized design with three replications was performed in order to study the effect of foliar application of proline (0, 50 and 100 mg L-1) on some morpho- physiological characteristics of pot marigold under drought stress (normal irrigation, 25, 50 and 75 % field capacity). The results showed that the highest fresh and dry weight of aerial organ, longevity of the flower on the plant, carotenoid and total chlorophyll were observed in normal irrigation+ proline 100 mg L-1. The highest fresh and dry root weight, root length and total antioxidant activity (DPPH) were for 75 % FC + proline 100 mg L-1. The highest plant height and number of flowers were in normal irrigation+ proline 50 mg L-1. The highest proline content was belonged to 25 % FC+ proline 100 mg L-1. In general, the results of this experiment showed that application of proline can partially compensate for the adverse effects of dehydration and on the other hand, despite the fact that the pot marigold plant is always able to survive in drought stress, it is recommended to irrigate 75% FC in order to increase pot marigold performance.