Dense plant cultivation is an efficient approach to improve maize production by maximizing the utilization of energy and nutrients. However, dense plant populations may aggravate the abortion rate of young grains, resulting in fewer kernels per ear. The rate and duration of grain-filling play decisive roles in maize grain yield. Therefore, to increase plant density, enhancing the grain-filling rate, extending the growth period of individual maize plants and regulating crop senescence would be the first priority. In this study, we examined the regulatory effects of GA4+7 under two application methods: shanks and silks were moistened by cotton full with GA4+7 solution at concentrations of 0, 10, 60, and 120 mg L−1. The results showed that GA4+7 improved the grain-filling rate by increasing the content of auxin, gibberellin, zeatin, and abscisic acid in grains compared to control plants. In addition, the auxin, gibberellin, and zeatin contents in the grains were positively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates. Moreover, GA4+7 increased the activities of superoxide dismutases, catalases, and peroxidases and reduced the malondialdehyde content in leaves compared with untreated plants. At the concentration of 60 mg L−1, GA4+7 showed the greatest effect on shank and silk applications (Sh-60 and Si-60) followed by 10 mg L−1 (Sh-10) for shank treatment and 120 mg L−1 (Si-120) for silk treatment. Our results suggest that a concentration of 60 mg L−1 GA4+7 for shank and silk application may be efficiently used for changing the level of hormones in grains and antioxidant enzymes in ear leaves, which may be useful for enhancing grain-filling rate and delaying leaf senescence, resulting in an increase in maize grain yield.
Dense plant cultivation is an efficient approach to improve the maize production by maximizing the utilization of energy and nutrient. However, dense plant populations may aggravate the abortion rate of young grains and result in fewer number of kernels per ear. Grain filling rate and duration play a decisive role in maize grain yield. Therefore, increasing plant density, consideration of enhancing the grain filling rate and duration of individual maize plant and regulating crop senescence would be the first priority. In this study, we examined the regulatory effects of GA4+7 under two application methods (shank-smearing and silk-smearing). Shank-soaking with GA4+7 at the rate of 0 (CK1), 10 (T1), 60 (T2), and 120 (T3) mg L−1, while silk-smearing at the rate of 0 (CK2), 10 (S1), 60 (S2), and 120 (S3) mg L-1 were used. The results showed that GA4+7 improved the grain filling rate by increasing the content of auxin, gibberellin and zeatin and abscisic acid in grains compared to control plants. In addition, The auxin, gibberellin and zeatin contents in the grains were positively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates; the abscisic acid level was positively correlated with the maximum grain weight and the maximum and mean grain-filling rates. Moreover, GA4+7 increased the activities of superoxide dismutases, catalases, peroxidases, and reduced the malondialdehyde content in leaves compared with untreated plants. At the rate of 60 mg L-1, GA4+7 showed the greatest effect for shank-smearing and silk-smearing (T2 and S2), followed by 10 mg L-1 (T1) for shank-smearing and 120 mg L-1 (S3) for silk-smearing. Our results suggest that application of 60 mg L-1 GA4+7 for smearing application could efficiently be used for changed the level of hormones in grains and antioxidant enzymes in ear leaf, would be useful for enhancing grain filling rate and delaying leaves senescence, and resulting in an increasing of maize grain yield.
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