Silicon seed inoculation enhances antioxidant defenses, physio-biochemical mechanisms and yield traits in maize hybrids under heat stress conditions at vegetative and tasseling stages

Context Heat stress, next to drought, is one of the major constraints for sustainable maize production in arid regions, and a threat to food security. Therefore, it is crucial to investigate mitigation strategies to reduce negative effects of heat stress. In this regard, silicon (Si) could be an ecofriendly mitigation strategy to ameliorate the adversative impacts of heat stress by modifying plant defense mechanisms in maize hybrids. Objective The study aims to explore the effects of Si seed inoculation on growth, and productivity of maize hybrids through improved physiological, antioxidants activity and osmolytes production under heats stress conditions. Methods Therefore, two years of field trials were conducted to evaluate the effect of Si seed inoculation (0.00, 1.50, 3.00, 4.50 and 6.0 mM), on the physiology, growth, antioxidant mechanisms, grain and biological yields of maize hybrids [DK-6103 (heat tolerant); SW-1080 (heat sensitive)] under control and heat stress conditions. The heat stress was imposed at V6 stage and 50% tasseling-VT-R0-R1 growth stages for a period of 8 consecutive days. Results The seed inoculation with 6 mM Si inoculation produced high grain yield and yield contributing traits compared to other Si levels when heat stress was imposed at V6 stage during year 2023 and 2024. Similarly, when the crop was exposed to heat stress at 50% tasseling-VT-R0-R1, the seed inoculation with 6 mM Si produced the maximum cob length (12.7 cm, 14.1 cm), grains per cob (456, 494), thousand kernel weight (TKW) (192.9 g, 204.5 g), grain yield (6.24 t ha −1 , 6.74 t ha −1 ) and biological yield (13.7 t ha −1 , 15.2 t ha −1 ), respectively, during year 2023 and 2024 compared to other levels of Si seed inoculation under heat stress scenarios. The findings are due to improved morpho-physiological attributes, and biochemical defense mechanisms under heat stress conditions. In addition, combined effects of E x G i.e. environment (optimum, heat stress at V6 stage and heat stress at 50% tasseling-VT-R0-R1) x genotype (DK-6103 and SW-1080) exhibited that DK-6103 produced more grain yield (6.02 t ha −1 , 6.50 t ha −1 ) and dry matter yield (11.4 t ha −1 , 12.6 t ha −1 ), during the two years (2023 and 2024), respectively, when heat stress was imposed at the V6 stage compared the ambient conditions. Moreover, SW-1080 produced a smaller grain (13.5%) and biological yield (14.8%) than maize hybrid DK-6103. Conclusions Therefore, the Si seed inoculation (6 mM) is the best studied treatment in reducing the negative impacts of heat stress and boosting the grain yield of maize hybrids by modulating the physiological, antioxidant and osmolytic mechanisms.