Changes in antioxidants and leaf pigments of safflower (Carthamus tinctorius L.) affected by exogenous spermine under water deficit

Water deficit is one of the most limiting factors for plant growth and production. Polyamines are osmo-active compounds and have important roles in plant resistance to water limitation. A pot experiment was undertaken in a greenhouse as factorial based on complete randomized block design with three replications to assess the physiological and biochemical responses of safflower to different levels of water supply (100% and 40% field capacity) and spermine (0, 40 and 60 µM). Ascorbate peroxidase and peroxidase activities (POX), malondialdehyde (MDA), hydrogen peroxide (H2O2), anthocyanins, soluble protein, soluble sugars and proline contents in shoots increased, while total phenols, flavonoids, and photosynthetic pigments significantly decreased due to water deficit. Foliar spray of spermine mitigated the adverse effects of water deficit by increasing the catalase, superoxide dismutase, POX activities, soluble proteins and photosynthetic pigments, and by decreasing MDA and H2O2 contents. Spermine could, therefore, play an important role in protecting photosynthetic system and cellular membranes during drought stress in safflower

Allelopathic effects of redroot pigweed (Amaranthus retroflexus L.) on germination & growth of cucumber, alfalfa, common bean and bread wheat

<p>Allelopathy is one of the important interactions among plants. Weeds can reduce crops productions in farms by their allelopathic effects. Redroot pigweed (<em>Amaranthus retroflexus </em>L.) is the most common weed in Iran with well-known allelopathic potential. In the presented experiment, the allelopathic effects of redroot pigweed on germination and growth of four important crop species including cucumber (<em>Cucumis sativus </em>L.), alfalfa (<em>Medicago sativa </em>L.), common bean (<em>Phaseulus vulgaris </em>L.) and bread wheat (<em>Triticum aestivum </em>L.) was studied. The effect of different concentrations of redroot pigweed leachate on seed germination and seedlings growth parameters of tested plants was significant, but not same in all studied species. Bread wheat and cucumber were more resistance in seed germination stage in comparison to common bean and alfalfa. Except alfalfa, all plant species showed certain rate of resistance in the most measured parameters. According to the obtained results, bread wheat and common bean were the most resistant species, cucumber was resistant at low concentration but sensitive at high concentration, and alfalfa was the most sensitive species to the redroot pigweed leachate treatments. Therefore, the cultivation of resistant plant species (such as bread wheat and common bean plants) in the regions with redroot pigweed’s invasion is appropriate way in management of the farms.<strong> </strong></p

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 Ч 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