Abstract
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.
Highlights
Maize is one of the most important cereal crops and is widely used as a food, fodder, and industrial raw material worldwide [1] Recently, the global production of maize has exceeded that of rice and wheat [2]
The results of field experiments showed that GA4+7 [m (GA4)+7 treatments significantly (p < 0.05) enhanced the ear characteristics and grain yield of maize compared with control treatments (Table 2)
Application of GA4+7 under high density leads to an increase in the level of indole-3-acetic acid (IAA), zeatin riboside (ZR), GA, and abscisic acid (ABA)
Summary
Maize is one of the most important cereal crops and is widely used as a food, fodder, and industrial raw material worldwide [1] Recently, the global production of maize has exceeded that of rice and wheat [2]. Plants 2020, 9, 978 has the potential to attain higher crop productivity [5,6,7,8], which leads to a greater leaf area index (LAI). Dense plant cultivation could greatly affect the grain-filling process and result in lower maximum and average maize grain-filling rates [13,14]. Dense plant populations increase the number of spikes per unit area but result in a decline of per-plant growth rates and exacerbate young kernel abortion, the ears per plant and kernels per ear have decreased [15,16,17,18]. While adopting high planting density in maize, improving the individual maize grain-filling rate is of great concern in modern crop systems
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