ORIGINAL ARTICLE

Physiological Responses of Safflower to Exogenous Putrescine under Water Deficit

Background: Drought stress is the most common abiotic stress factor which reduces the plant growth and development more than other factors. For this reason, identification of effective factors to increase drought tolerance of plants is necessary requirement. Many reports have been focused on the involvement of polyamines in plant response to abiotic stresses such as drought. Polyamines as growth regulators play important roles in keeping cell membrane stability and reducing ROS generation under water deficit. Carthamus tinctorius is an industrial, medicinal and oil crop from Asteraceae family. Many studies in other plants showed that polyamines increase tolerance to environmental stresses, but physiological responses of water-stressed safflower plants to putrescine is not clear. Thus, this research was carried out to investigate the physiological changes in safflower under different levels of water supply (100% and 40% field capacity) treated by putrescine (0, 40 and 60 µM). The experiment was conducted in a greenhouse as factorial arrangement based on complete randomized block design with three replications.
Results: Interaction of irrigation × putrescine was significant for all traits. Water deficit significantly decreased growth parameters, leaf relative water content, photosynthetic pigments, and soluble protein. APX, CAT, POX and SOD activities, lipid peroxidation, H₂O₂, electrolyte leakage, proline, and soluble sugar contents increased under water deficit. Putrescine application alleviated drought stress injury by decreasing MDA and hydrogen peroxide contents, and increasing photosynthetic pigments, antioxidant enzymes activities, anthocyanin and soluble protein contents, leading to a better growth of plants. Foliar spray of 60 µM putrescine was the most beneficial treatment for improving safflower growth under water limitation.
Conclusions: Water deficit induced oxidative stress and reduced safflower growth. Exogenous putrescine promoted drought tolerance of plants via increasing antioxidant enzymes activities, anthocyanin, soluble protein contents and decreasing lipid peroxidation, electrolyte leakage and H₂O₂ contents. Overall, 60 µM putrescine was the best treatment for alleviating harmful effects of drought on safflower plants.