关键词: 夏玉米, 高温胁迫, 根系形态建构, 抗氧化特性, 化学调控

Abstract:

【Objective】High temperature and heat damage frequently occur in the summer maize production areas of the Huang-Huai-Hai area, which severely inhibits the growth and development and impairs functions such as water and nutrient uptake and storage of maize roots. Elucidating the effects of the ethephon-glycine betaine-salicylic acid (EGS) mixture on root system architecture and yield formation under heat stress could provide the technical support and theoretical basis for establishing chemical regulation strategies for heat resistance and yield increase in summer maize cultivation in the Huang-Huai-Hai area. 【Method】Field experiments were conducted at the Xinxiang Experimental Station of the Chinese Academy of Agricultural Sciences in 2022 and 2023. Using Yudan 9953 (YD9953) and Zhengdan 958 (ZD958) as test materials, chemical regulation treatment and heat stress treatment were established. For the chemical regulation treatment, the EGS mixture was sprayed on the leaves at the 6th-leaf stage (V6), while an equal amount of water was applied to the control group. Heat stress treatments were implemented for 4 days at the 9th-leaf stage (V9) and tasseling stage (VT), respectively, with field heating treatment (H) and normal temperature control (CK). The study aimed to investigate the effects of EGS treatment on root system architecture, physiological functions, and yield of maize under heat stress during different growth stages. 【Result】Under heat stress treatment in V9 and VT stages, compared with normal temperature control, in terms of root system architecture, the root dry weight, root-shoot ratio, the number of roots, root length, root surface area and root volume of YD9953 and ZD958 were significantly decreased; in terms of root physiological functions, root activity and activities of root antioxidant enzymes (SOD, POD, and CAT) were decreased significantly, while malondialdehyde (MDA) content increased significantly. Consequently, yield components and final output were severely compromised, with significant reductions in kernel number per ear, 100-kernel weight, and grain yield. Compared with heat stress treatment, EGS-H treatment improved root system architecture, alleviated the inhibition effect of heat stress on the number of roots, especially the number of aerial roots, significantly increased the root dry weight, root length, root surface area and root volume, and root volume was significantly positively correlated with yield. EGS-H treatment enhanced root physiological functions, significantly increased root activity and root antioxidant enzymes (SOD, POD, and CAT), while membrane peroxidation degree was significantly decreased. EGS-H treatment significantly increased the kernel number per ear and yield. After heat stress was applied at the V9 and VT stages, compared with heat stress treatment, EGS-H treatment increased the yield of YD9953 by an average of 19.42% and 19.56% in 2022, respectively, and by 14.40% and 17.95% in 2023, respectively. For ZD958, the yield increased by 9.81% and 13.02% in 2022, respectively, and by 7.68% and 7.78% in 2023, respectively. 【Conclusion】The EGS mixture could regulate the root system architecture of summer maize under heat stress, promote root growth and development, and increase maize yield under heat stress.

Key words: summer maize, heat stress, root system architecture, antioxidant properties, chemical regulation