The
steroid hormones, including brassinosteroids, regulate plant
growth under stress. It is hypothesized that 24-epibrassinosteroids
(24-EBR) can affect safflower (Carthamus tinctorius) biochemical properties, crop yield, and oil content under drought
stress. The objective of our study was to determine the response of
three safflower genotypes (Goldasht, Faraman, and Sina) to exogenous
24-EBR (0 and 10–7 M) under drought stress, including
85, 65, and 45% of field capacity in 2015. Stress decreased chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid,
relative water content (RWC), seed yield, and oil percentage. The
activities of superoxide dismutase (SOD), catalase (CAT), polyphenol
oxidase (PPO), and proline contents increased in response to either
drought stress or 24-EBR. Genotypes behaved significantly different
under stress. 24-EBR significantly increased plant chlorophyll contents
and oil percentage, and it significantly reduced the malondialdehyde
(MDA) content via increasing the proline and carotenoid contents under
stress. 24-EBR can increase safflower oil and seed yield under drought
stress.
Water deficit is one of the most important environmental stresses that adversely affect crop growth and production and mycorrhizal fungi and symbiotic bacteria have important role in resistance to drought stress. The effect of biofertilizers on alfalfa stress tolerance was studied at the greenhouse condition. Treatments comprised three water-deficit stresses (35%, 55% and 75% of field capacity) and four seeds inoculations (Glomus mosseae, Sinorhizobium meliloti, G. mosseae + S. meliloti and non-inoculated). Water-deficit stress decrease cell membrane stability (39%), total Chl (24.05%), carotenoid (35.55%), quantum yield (50.64%) and forage yield (28.20%), while increased the proline and soluble sugars content (68.55 and 46.53% respectively) and osmotic potential (45.84%). The inoculation of seeds increased the capability of the plants in counteracting the stress, so that the production of compatible solutes was increased and the photosynthetic indices, proline, osmotic potential, membrane stability and forage yield were improved by seed inoculation. Mycorrhiza improved photosynthetic indexes and proline, but bacteria had more efficacy on membrane stability and forage yield. However, double inoculation due to the synergistic effect of mycorrhiza and Sinorhizobium, had the greatest effect than Solitary inoculation. Our results suggest that biofertilized alfalfa plants were better adapted than non-biofertilized ones to cope with water deficit.
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