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Maize kernel growth is sensitive to heat stress, which is predicted to result in yield loss. However, the response of maize to short-term heat stress during different kernel-growth stages is still not clear. A 3-year field experiment, included two heat-stress treatments (LSH, lag-stage heat stress; FSH, effective-filling-stage heat stress), was conducted in 2019–2021. The results showed that LSH and FSH significantly reduced the grain yield by 8.7–14.9% and 11.6–17.6%, respectively, compared with the control (CK). LSH mainly reduced the kernel number per ear, and FSH mainly reduced the kernel weight. Heat stress reduced the SPAD and chlorophyll content during the effective-filling stage, but not in the lag stage. Photosynthesis was obviously reduced under heat stress during both stages; however, the photosynthesis rate during the lag stage was higher than during the effective-filling stage. The decreased amplitude of dry matter under LSH was higher than under FSH during the heating period. However, there was no difference between the CK and LSH samples in terms of dry-matter accumulation from the end of heat stress to harvest, which was significantly reduced under FSH. Additionally, decreased starch-synthesis-related enzyme activity, i.e., adenosine diphos-phoglucose pyrophosphprylase, contributed to the kernel number and kernel weight loss in LSH and FSH, respectively. The kernel-growth rate (per ear) was lowered, but the growth duration was not shortened in this study. Consequently, LSH mainly reduced the photosynthesis rate (Pn), resulting in kernel abortion and yield penalty. FSH mainly reduced the Pn and chlorophyll content, which reduced the kernel weight, and increased yield loss. [ABSTRACT FROM AUTHOR]

Lodging is a major constraint to maize productivity and harvesting mechanization in the North China Plain. EDAH (contains ethephon and diethyl aminoethyl hexanoate) is a novel growth regulator, which had been proved to enhance maize lodging resistance and increase yield, especially under high plant density. However, lodging still happens when recommended dose of EDAH was foliar sprayed in many previous reports. Therefore, a field experiment with normal dose (T1) and increased dose (T2) of EDAH was conducted to further enhance maize lodging resistance under different plant densities. Results indicated that T2 significantly reduced plant height and ear height, and obviously increased bending strength (P < 0.05), i.e., increasing EDAH dose more obviously enhanced maize lodging resistance. Concurrently, EDAH distinctly inhibited maize growth which resulted in lower leaf area index (LAI) and leaf area duration (LAD) after silking. However, both leaf photosynthetic rate and chlorophyll content during filling stage were not significantly (P > 0.05) changed by EDAH. Consequently, maize grain yields under T1 and T2 were reduced by 3.2–8.5% and 10.9–13.6% under optimized density (7.5 plants m2−) in this study, respectively. Nevertheless, EDAH did not reduce maize yield under high density (9.0 plants m2−) due to relative high LAI (5.3–5.6). We concluded that high dose EDAH further enhanced lodging resistance with reduced grain yield under optimized density, but maintained grain yield under high plant density. Results of this study provided a critical strategy to lower lodging risk and increase maize grain yield. [ABSTRACT FROM AUTHOR]

Waxy maize starch serves as a pivotal component in global food processing and industrial applications, while high temperature (HT) during the grain-filling stage seriously affects its quality. Salicylic acid (SA) has been recognized for its role in enhancing plant heat resistance. Nonetheless, its regulatory effect on the quality of waxy maize starch under HT conditions remains unclear. In this study, two waxy maize varieties, JKN2000 (heat-tolerant) and SYN5 (heat-sensitive) were treated with SA after pollination and then subjected to HT during the grain-filling stage to explore the effect of SA on grain yield and starch quality. The results indicate that exogenous SA under HT treatment led to an increase in kernel weight and starch content in both varieties. Moreover, SA reduced the HT-induced holes on the surfaces of starch granules, enlarged the starch granule size, elevated the amylopectin branching degree, and reduced amylopectin average chain length. Consequently, improvements of pasting viscosity and the decrease of retrogradation percentage of starch were observed with SA under HT. Exogenous SA reduced HT-induced rapidly digestible starch content in SYN5, but had no significant effect on that in JKN2000. In summary, SA pretreatment effectively alleviated the detrimental effects of HT on starch pasting and thermal properties of waxy maize. • HT destroyed the starch structure, and changed the physicochemical properties and digestibility. • SA ensured the integrity of starch granules and enlarged the granule size under HT. • SA decreased the average chain length and increased the branching degree of amylopectin under HT. • SA improved the pasting and thermal properties and vitro digestibility of starch under HT. [ABSTRACT FROM AUTHOR]