Response of Seed Vigor and Hardseedness of Two Annual Medics under Drought Stress and Foliar Application of Iron and Zinc

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To determine the effects of drought stress and Fe and Zn spraying on two annual medics, namely, Medicago polymorph cv Serena and Medicago scutellata cv Comertial, a field experiment as a split factorial based on a randomized complete blockdesign in 3 replications in Allborze Agricultural Research Center, in Karaj was conducted. Spraying treatments include distilled water (control), Fe, Zn and Fe+Zn, and drought stress include complete irrigation as control, irrigation until 10 days before flowering, irrigation until %50 flowering, and irrigation until maturity of first pod from the lower part of plant. For laboratory experiments, osmotic treatments of -3, -6 and -9 bars using polyethyleneglycol 6000 and distilled water as control were used to evaluate produced seed response to drought stress. The result showed that Fe content of seed in spraying treatment of Fe and Fe+Zn increased by 68% and %13, respectively. Amount of Fe in spraying treatment of Zn, was lower than control (by %15). Fe content in Scutellata seed was 181 mg/kg lower than Polymorpha and Zn content was %10 higher than Polymorpha. Significant and negative correlation between Zn and Fe in seeds (r=-62**) was achieved. Interaction of genotypes and spraying in different levels of drought stress showed that Fe content in Scutellata seeds in the second, third and fourth levels of drought were 8, 6 and %33 higher than complete irrigation, respectively. Percentage of seed hardness in the second, third and fourth levels of stress under spraying treatments of Zn, Fe+Zn and Fe+Zn was 28, 30 and %22, respectively. By increasing osmotic potential from -3 to -9 bars, seedling growth was increased under Fe+Zn spraying up to 0.5-15 fold in all level of stress in compare to control treatment. Moreover, under the aforementioned conditions dry weight of root was 10-48% higher in Scutellata than control. Also shoot dry weight increased by 20-60 % in spraying treatment of Fe+Zn under stress conditions. Seedling vigor in spraying treatment of Fe+Zn was 1.5 -3 fold better than control. Generally, iron plus zinc and iron spray treatments were valuable treatments to produce seedlings with high vigor and ability to withstand drought conditions.

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