Evaluation of the effect of putrescine on morphological and physiological indices of Giant Milkweed Seedlings (Calotropis procera Ait.) under drought conditions

Given the importance of Giant Milkweed shrub in reclamation of deserts and arid regions, and position of Iran in low rainfall and arid areas, so far enough research has not been done to understand the morpho-physiological properties of the Giant Milkweed shrub under drought stress conditions and to determine the status of putrescine in reducing the devastating effects of drought. For this purpose, a field experiment was conducted in a split plot randomized complete block design with four replications to determine the effect of putrescine on some morphological and physiological characteristics of Giant Milkweed seedlings under drought stress conditions in Research Farm of the University of Hormozgan. The main factor included five levels of irrigation (1 (control), 3, 6, 9 and 12 days irrigation intervals) and putrescine treatment by foliar sprays at 3 steps every 20 days at five levels (0, 0.5, 1, 1.5, 2 mM) in sub plots. Results showed that an increase in irrigation interval up to 12 days reduced leaf area, fresh and dry weight of shoots, fresh and dry weight of roots, and chlorophyll content. Also, increased irrigation interval up to 12 days increased proline content, superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase enzymes activities. Increase in the concentration of putrescine, led to a significant increase in leaf area, fresh and dry weights of shoots and roots, chlorophyll content, proline content, and superoxide dismutase, peroxidase, and ascorbate peroxidase enzymes activities in the leaves. The best putrescine treatment to reduce the devastating effects of drought was observed at concentration of 2 mM. According to the results obtained, the use of putrescine to establish the plant in dry conditions is recommended.