Effects of shading after pollination on kernel filling and physicochemical quality traits of waxy maize

Spraying exogenous hormones alleviate impact of weak-light on yield by improving leaf carbon and nitrogen metabolism in fresh waxy maize

Insufficient light during the growth periods has become one of the main factors restricting maize yield with global climate change. Exogenous hormones application is a feasible measure to alleviate abiotic stresses on crop productivity. In this study, a field trial was conducted to investigate the effects of spraying exogenous hormones on yield, dry matter (DM) and nitrogen (N) accumulation, leaf carbon and N metabolism of fresh waxy maize under weak-light stress in 2021 and 2022. Five treatments including natural light (CK), weak-light after pollination (Z), spraying water (ZP1), exogenous Phytase Q9 (ZP2) and 6-benzyladenine (ZP3) under weak-light after pollination were set up using two hybrids suyunuo5 (SYN5) and jingkenuo2000 (JKN2000). Results showed that weak-light stress significantly reduced the average fresh ear yield (49.8%), fresh grain yield (47.9%), DM (53.3%) and N accumulation (59.9%), and increased grain moisture content. The net photosynthetic rate (Pn), transpiration rate (Tr) of ear leaf after pollination decreased under Z. Furthermore, weak-light decreased the activities of RuBPCase and PEPCase, nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in ear leaves, and increased malondialdehyde (MDA) accumulation. And the decrease was greater on JKN2000. While ZP2 and ZP3 treatments increased the fresh ear yield (17.8%, 25.3%), fresh grain yield (17.2%, 29.5%), DM (35.8%, 44.6%) and N (42.5%, 52.4%) accumulation, and decreased grain moisture content compared with Z. The Pn, Tr increased under ZP2 and ZP3. Moreover, the ZP2 and ZP3 treatments improved the activities of RuBPCase, PEPCase; NR, GS, GOGAT; SOD, CAT, POD in ear leaves, and decreased MDA content during grain filling stage. The results also showed the mitigative effect of ZP3 was greater than ZP2, and the improvement effect was more significant on JKN2000.

Shading Stress at Different Grain Filling Stages Affects Dry Matter and Nitrogen Accumulation and Remobilization in Fresh Waxy Maize

Shading stress caused by plum rain season, which overlapped with grain filling process of fresh waxy maize in Southern China, significantly affected crop productivity. In order to investigate the effects of shading at different stages after pollination on the yield, accumulation, and remobilization of dry matter and nitrogen (N) in fresh waxy maize, field experiments were conducted, including shading at 1-7 (Z1), 8-14 (Z2), 15-21 (Z3), and 1-21 (Z4) days after pollination in 2020 and 2021. The results showed that shading reduced the fresh ear and grain yield and increased moisture content in Suyunuo5 (SYN5) and Jingkenuo2000 (JKN2000) compared to natural lighting treatment (CK). The ear yield decrease was more severe in Z4 (43.5%), followed by Z1 (29.7%). Post-silking dry matter and N accumulation and remobilization were decreased under shading stress, and those were lowest in Z4, followed by Z1. The remobilization of pre-silking dry matter and N were increased by shading stress, and the increase was highest in Z4, followed by Z1. The harvest index of dry matter and N was lowest in Z4 and second-lowest in Z1. In conclusion, shading decreased yield by affecting accumulation and remobilization of post-silking dry matter and N, and the impact was more serious when it introduced early during grain filling stage in fresh waxy maize production.

Fertilization time of slow-release fertilizer affects the physicochemical properties of starch from spring-sown waxy maize

BACKGROUND

Slow-release fertilizer is widely used in cereal crop production because it is ecofriendly and laborsaving. Effects of different application stages (zero-, three-, and six-leaf stages, denoted as SN0, SN3, and SN6, respectively) of slow-release (N/P₂ O₅ /K₂ O = 225/75/75 kg ha^-1 ) fertilizer on physicochemical properties of starch from spring-sown waxy maize were investigated in 2018 and 2019. Application of traditional fertilizer (NCK, compound fertilizer; N/P₂ O₅ /K₂ O = 75/75/75 kg ha^-1 ) at sowing time and urea (N = 150 kg ha^-1 ) at six-leaf stage was designated as the control.

RESULTS

In comparison to the NCK, SN0 reduced grain starch content by 4.9%. Meanwhile, SN3 and SN6 did not affect this parameter. Nevertheless, all treatments, particularly SN6, increased average starch granule size. The slow-release fertilizer reduced proportion of chains with degree of polymerization (DP) > 24. Relative to NCK, SN6 increased starch crystallinity in both years, whereas SN0 and SN3 increased it in 2018 but reduced it in 2019. SN0 reduced peak, trough, and final viscosities, whereas SN3 and SN6 produced similar starch viscosities to those produced by NCK. No fertilizer mode affected gelatinization parameters, but SN6 produced a low retrogradation percentage. In comparison to data for 2018, starch produced in 2019 showed a small granule size, and a high proportion of short amylopectin chains. These properties endowed starch with high viscosity and low retrogradation percentage.

CONCLUSION

In spring-sown waxy maize production, applying slow-release fertilizer at the six-leaf stage produced starch with high viscosity and low retrogradation tendency by enlarging granule size, increasing crystallinity, and reducing the proportion of long chains. © 2021 Society of Chemical Industry.

Post-Silking Shading Stress Affects Leaf Nitrogen Metabolism of Spring Maize in Southern China

Lower sunlight caused by overcast skies from June to July in Southern China is one of the main environmental stresses that frequently occur and affect the post-silking growth and grain development of spring maize. In this study, a field trial involving four maize hybrids as materials was conducted to investigate the effects of post-silking shading stress (30% and 50% light deprivation) on leaf nitrogen metabolism and biomass accumulation during maize growing seasons in 2016 and 2017. Results indicated that 30% and 50% shading stress caused the grain yield to decrease by 47.3% and 69.6%, respectively. Plant post-silking biomass accumulation was decreased by shading, whereas the translocation from pre-silking assimilates in the vegetative organs was increased by shading. This change was sharply observed when the plants were deprived of more sunlight intensity. The leaf relative chlorophyll (soil and plant analyzer development (SPAD) value) and soluble protein contents were considerably decreased by shading under 50% light deprivation condition. The activities of nitrate reductase, glutamine synthetase and glutamate synthase that are involved in nitrogen metabolism were downregulated by shading stresses. In conclusion, nitrogen metabolism was disturbed by shading, which induced the decrease in post-silking dry matter accumulation, ultimately resulting in grain yield loss.