Frontiers in Maize Ecophysiology

Plants of inbred maize lines are characterized by low vigor due to their high rates of homozygosity and may, therefore, benefit from additional nutrients and biostimulants supplied via foliar spraying. The present study innovatively investigated the effects of foliar treatment with three commercial organic-mineral fertilizers/biostimulants on a male-sterile inbred line of maize at the five-leaf stage. The three fertilizers were characterized by their following content: (i) NPK + hydrolyzed animal epithelium + micronutrients (named ‘NPK + Hae + micro’), (ii) NK + humified peat (named ‘NK + Hp’), and (iii) PK + Ascophyllum nodosum extracts (named ‘PK + An’). The resulting shoot and root growth and seed yield and quality were compared to a control (C). Both NPK + Hae + micro and PK + An treatments enhanced root growth in the top 20 cm soil layer at the ten-leaf stage: root dry biomass increased by 80 and 24%, respectively, and the volumetric root length density by 61 and 17%. The two treatments also allowed for a larger number of commercial seeds to be produced (on average +16 bags per gross hectare vs. C) owing to a better seed caliber, which consequently reduced rates of seed disposal (−11 and −20% for PK + An and NPK + Hae + micro, respectively) and, in the case of NPK + Hae + micro, due to an increment in the number of kernels per ear (+5% vs. C). These effects were not associated with any significant changes in shoot growth, height, or leaf net CO₂ assimilation. In this preliminary trial, peak commercial benefit was obtained with the use of hydrolyzed epithelium together with macro- and micronutrients. Further investigation into application timing and dose, and the means by which these products alleviate the effects of low vigor and stress conditions observed particularly under mechanical emasculation is, however, necessary for their full exploitation in the production of hybrid maize seeds. Full article

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. Full article

Carbon nanotubes (MWCNTs) and nano-silica (nano-SiO₂) are widely used in the field of life science because of their special physical and chemical properties. In this study, the effects of different concentrations of MWCNTs (0 mg·L⁻¹, 200 mg·L⁻¹, 400 mg·L⁻¹, 800 mg·L⁻¹ and 1200 mg·L⁻¹) and nano-SiO₂ (0 mg·L⁻¹, 150 mg·L⁻¹, 800 mg·L⁻¹, 1500 mg·L⁻¹ and 2500 mg·L⁻¹) on maize seedling growth and relative mechanisms were explored. The main results are as follows: MWCNTs and nano-SiO₂ can promote the growth of maize seedlings, and promote plant height, root length, the dry and fresh weight of seedlings, root–shoot ratio and so on. The ability to accumulate dry matter increased, the relative water content of leaves increased, the electrical conductivity of leaves decreased, the stability of cell membranes improved and the water metabolism ability of maize seedlings increased. The treatment of MWCNTs with 800 mg·L⁻¹ and nano-SiO₂ with 1500 mg·L⁻¹ had the best effect on seedling growth. MWCNTs and nano-SiO₂ can promote the development of root morphology, increase root length, root surface area, average diameter, root volume and total root tip number and improve root activity, so as to improve the absorption capacity of roots to water and nutrition. After MWCNT and nano-SiO₂ treatment, compared with the control, the contents of O₂·⁻ and H₂O₂ decreased, and the damage of reactive oxygen free radicals to cells decreased. MWCNTs and nano-SiO₂ can promote the clearance of reactive oxygen species and maintain the complete structure of cells, so as to slow down plant aging. The promoting effect of MWCNTs treated with 800 mg·L⁻¹ and nano-SiO₂ treated with 1500 mg·L⁻¹ had the best effect. After treatment with MWCNTs and nano-SiO₂, the activities of key photosynthesis enzymes PEPC, Rubisco, NADP-ME, NADP-MDH and PPDK of maize seedlings increased, which promoted the opening of stomata, improved the fixation efficiency of CO₂, improved the photosynthetic process of maize plants and promoted plant growth. The promoting effect was the best when the concentration of MWCNTs was 800 mg·L⁻¹ and the concentration of nano-SiO₂ was 1500 mg·L⁻¹. MWCNTs and nano-SiO₂ can increase the activities of the enzymes GS, GOGAT, GAD and GDH related to nitrogen metabolism in maize leaves and roots, and can increase the content of pyruvate, so as to promote the synthesis of carbohydrates and the utilization of nitrogen and promote plant growth. Full article

The primary parts of corn stalks are the leaves and the stems, which comprise the cortex and the pith. Corn has long been cultivated as an grain crops, and now it is a primary global source of sugar, ethanol, and biomass-generated energy. Even though increasing the sugar content in the stalk is an important breeding goal, progress has been modest in many breeding researchers. Accumulation is the gradual rise in quantity when new additions are made. The challenging characteristics of such sugar content in corn stalks are below the protein, bio-economy, and mechanical injury. Hence, in this research, plant water-content-enabled micro-Ribonucleic acids (PWC-miRNAs) were designed to increase the sugar content in corn stalks following an accumulation rule. High-throughput sequencing of the transcriptome, short RNAs, and coding RNAs was performed here; leaf and stem degradation from two early-maturing Corn genotypes revealed new information on miRNA-associated gene regulation in corn during the sucrose accumulation process. For sugar content in corn stalk, PWC-miRNAs were used to establish the application of the accumulation rule for data-processing monitoring throughout. Through simulation, management, and monitoring, the condition is accurately predicted, providing a new scientific and technological means to improve the efficiency of the construction of sugar content in corn stalks. The experimental analysis of PWC-miRNAs outperforms sugar content in terms of performance, accuracy, prediction ratio, and evaluation. This study aims to provide a framework for increasing the sugar content of corn stalk. Full article

In the North China Plain, the excessive application of nitrogen (N) fertilizer for ensuring high yield and a single application at sowing for simplifying management in farmer practice lead to low N use efficiency and environmental risk in maize (Zea mays L.) production. However, it is unclear whether and how late split application with a lower level of N fertilizer influences maize yield. To address this question, a two-year field experiment was conducted with two commercial maize cultivars (Zhengdan 958 and Denghai 605) using a lower level of N input (180 kg ha⁻¹) by setting up single application at sowing and split application at sowing and later stages (V12, R1, and R2) with four different ratios, respectively. The maize yield with split-applied 180 kg ha⁻¹ N did not decrease compared to the average yield with 240 kg ha⁻¹ N input in farmer practice, while it increased by 6.7% to 11.5% in the four N split-application treatments compared with that of the single-application control. Morphological and physiological analyses demonstrated that late split application of N (i) increased the net photosynthetic rate and chlorophyll content and thus promoted the photosynthetic efficiency during the reproductive stages; (ii) promoted the sink capacity via improved kernel number, endosperm cells division, and grain-filling rate; and (iii) increased the final N content and N efficiency in the plant. Therefore, we propose that late split application of N could reduce N fertilizer input and coordinately improve N efficiency and grain yield in summer maize production, which are likely achieved by optimizing the source–sink relations during the grain-filling stage. Full article

Heat stress around flowering is harmful to maize growth and yield. Ear traits are closely related to yield; however, the effects of heat stress before and after flowering on ear development and yield traits remain unclear for different heat-tolerant cultivars. In this study, field experiments were conducted in 2020 and 2021, including (i) three sowing dates, (ii) three temperature regimes: control (CK), heated before silking (V9-R1, TBS) and heated after silking (R1-R1 + 15 d, TAS), and (iii) two hybrids (ZD958: heat-tolerant; DH605: heat-sensitive). The results showed that heating had negative effects on all surveyed ear and yield traits except for increased ear length under TBS. The negative effects were larger (i) for TAS than for TBS, (ii) for DH605 than for ZD958, and (iii) for kernel number per plant (KNP) than for kernel weight (KW). The decreased ear traits were a result of a decreased growth rate during rapid ear growth periods. Floret pollination failure and kernel abortion were the main reasons for the decrease in KNP, mainly depending on the daily maximum temperature during V15-R1 + 7 d. The strong linear relationships between ear and yield traits suggested that ear traits could be used as important indicators for breeding heat-resistant varieties in the future. Full article

To explore the efficiency of selenium (Se) fertilizer application in dryland maize, we tested five Se fertilizer application treatments: 0 g ha⁻¹ (Se0), 75 g ha⁻¹ (Se1), 150 g ha⁻¹ (Se2), 225 g ha⁻¹ (Se3), and 300 g ha⁻¹ (Se4). Compared with Se0, Se2 increased the leaf area, chlorophyll content, internode length, plant height, and ear height by 7.95%, 3.20%, 13.19%, 1.89%, and 7.98%, respectively. Se2 and Se3 significantly affected the stem internode diameter, cortex thickness, and cellulose content, which were positively correlated with lodging resistance. Compared with Se0, Se3 promoted the contents of soluble sugar, crude protein, crude fat, and starch in grains, which increased by 9.48%, 6.59%, 1.56%, and 4.82%, respectively. It implies that maize grain application of Se significantly improves their Se content. Se1 did not observably influence the growth of maize, and the promoting effect of Se4 on maize decreased. The lodging resistance of maize as analyzed by Pearson correlation analysis correlated with the application of Se fertilizer. It proved that higher yield, grain quality, grain Se content, and lodging resistance of stems were concerned with Se fertilizer application in the range of 150–225 g ha⁻¹. The results provide useful information for Se fertilizer treatment in dryland maize. Full article

The research aimed to assess the contribution of fertilizer, density, and row spacing in integrated cultivation measures and identify their regulation mechanism on canopy architecture and factors in biomass accumulation in spring maize. Zhengdan 958 was used as the experimental material, and the optimum mode (OM) was identified based on a preliminary experiment, including the optimal fertilizer management, suitable plant density and wide-narrow row spacing, and dramatic yield performance (11,445.16 kg ha⁻¹ in 2017). Then, the effects of these practices on maize canopy structure performance were analyzed using the omission factors design experiment in optimum mode (OM). Treatments were set as follows: without fertilization (OM-F), without density (OM-D), and without wide-narrow plant spacing (OM-S). The results showed that the contribution of fertilization was maximum (23.85%), the second was intensive planting (16.05%), which promoted nitrogen accumulation and transport in leaves and stems via increased leaf area index and dry matter accumulation around the anthesis simultaneously, elevating the radiation utilization efficiency of the canopy and allowing a higher grain weight to be obtained. Wide-narrow row spacing yield contribution is minimum among the measures (8.649%), which could regulate the leaf and radiation transmittance in the middle and bottom layer of the canopy, while increasing the nitrogen accumulation of leaves and stalks in the silking stage, then significantly enhance the nitrogen transport and the matter accumulation of maize after anthesis. Our results showed that fertilizer management and density were the essential practices for integrated cultivation mode for northeast China. Moreover, wide-narrow row planting was advocated if permitted, which could elevate the utilization efficiency of radiation to 1%, and the yield of more than 11,000 kg ha⁻¹ was obtained in Northeast China. Full article

Understanding the biological roles of root hairs is key to projecting their contributions to plant growth and to assess their relevance for plant breeding. The objective of this study was to assess the importance of root hairs for maize nutrition, carbon allocation and root gene expression in a field experiment. Applying wild type and root hairless rth3 maize grown on loam and sand, we examined the period of growth including 4-leaf, 9-leaf and tassel emergence stages, accompanied with a low precipitation rate. rth3 maize had lower shoot growth and lower total amounts of mineral nutrients than wild type, but the concentrations of mineral elements, root gene expression, or carbon allocation were largely unchanged. For these parameters, growth stage accounted for the main differences, followed by substrate. Substrate-related changes were pronounced during tassel emergence, where the concentrations of several elements in leaves as well as cell wall formation-related root gene expression and C allocation decreased. In conclusion, the presence of root hairs stimulated maize shoot growth and total nutrient uptake, but other parameters were more impacted by growth stage and soil texture. Further research should relate root hair functioning to the observed losses in maize productivity and growth efficiency. Full article

Reasonable fertilization of nitrogen (N) and potassium (K) had significant effects on maize growth. In this experiment, two N levels (N180 and N225 kg ha⁻¹) and four K treatments (K0, K75, K150 and K75 + 75 kg ha⁻¹) were set to study the effects of combined application of N and K on the grain yield and quality of waxy maize. The results showed that grain yield increased with increasing K under the same N level, and top-dressing K further increased the grain yield. K application increased starch content significantly at N180 and decreased significantly at N225, while the protein content increased significantly at the two N levels. The grain starch content with the K75 + 75 treatment increased by 5.8% and 9.0% compared with K150 at the two N levels, and the protein content decreased by 2.9% and 4.7%. Application of K increased the retrogradation enthalpy (ΔH_ret) and retrogradation percentage (%R) at N180. At N225, the ΔH_ret and %R of K75 and K150 decreased, while those of K75 + 75 increased. The ΔH_ret and %R under K75 + 75 at N180 were lower than N225. Under these experiment conditions, 75 kg ha⁻¹ K₂O at sowing date and top-dressed 75 kg ha⁻¹ K₂O at jointing stage (V6) under the conditions of appropriate N reduction could not only effectively improve the pasting and thermal properties of waxy maize flour, but also stabilized the grain yield. Full article

To explore the effects of iminodisuccinic acid (a chelating agent) on maize (Zea mays L.) seed germination under lead (Pb) stress, we comparatively analyzed the effects of applying different concentrations of iminodisuccinic acid (0, 5, 20, and 100 mmol·dm⁻³) and combined an addition of exogenous substances regulating reactive oxygen species production on maize seed germination, seedling growth, H₂O₂ content, NADPH oxidase activity, and antioxidant enzyme activities under Pb-stressed and Pb-free conditions. Iminodisuccinic acid (100 mmol·dm⁻³) significantly delayed seed germination under normal germination conditions and alleviated the inhibitory effects of Pb stress (20 mmol·dm⁻³) on seed germination. Under normal conditions (without Pb stress), the iminodisuccinic acid-induced inhibition of seed germination was enhanced by treatment with dimethylthiourea (a specific scavenger of reactive oxygen species) or diphenyleneiodonium chloride (a specific inhibitor of NADPH oxidase), but diminished by treatment with H₂O₂, CaCl₂, diethyldithiocarbamic acid (a specific inhibitor of superoxide dismutase), or aminotriazole (a specific inhibitor of catalase). Under Pb stress, iminodisuccinic acid partially eliminated the excessive H₂O₂ accumulation, improved superoxide dismutase and catalase activity, and weakened the high NADPH oxidase activity. In addition, Ca²⁺ chelation may be essential for maintaining the reactive oxygen species’ balance and improving seed germination and seedling growth by iminodisuccinic acid supplementation in maize under Pb stress. The proposed iminodisuccinic acid supplementation-based method improved maize seed germination in Pb-polluted soil. Full article

Increasing planting density is an effective way to improve maize yield, but high plant populations often cause a lodging problem. This experiment was conducted to investigate the effect of increasing planting density on stalk lodging resistance and grain yield, and to explore the effects on stalk and yield properties of spraying ethephon in densely planted summer maize. The summer maize hybrid, Xundan20 (XD20), was used as experimental material. It was grown by spraying water (CK) or ethephon (E) at BBCH (BASF, Bayer, Ciba-Geigy and Hoechst) 17 under three different planting densities of 60,000 plants ha⁻¹ (L), 75,000 plants ha⁻¹ (M) and 90,000 plants ha⁻¹ (H) in order to explore the possibility of synergistic improvement in stalk lodging resistance and grain yield. The results from this experiment suggested that the gravity center height of densely planted summer maize was significantly increased, the stem diameter, area and number of vascular bundles were significantly decreased and the dry weight per unit internode was significantly decreased, thereby weakening the stalk rind penetration strength and bending performance, resulting in a significant increase in lodging percentage. The ear height was significantly decreased and the SPAD (soil and plant analysis development) and canopy light transmittance were increased after spraying ethephon; then, the internode dry weight per unit length was increased and the stalk rind penetration strength and bending performance were enhanced so as to significantly reduce the lodging percentage and increase the grain yield. The correlation analysis further showed that lodging percentage was significantly negatively correlated with stem diameter, area and number of vascular bundles and stalk bending performance, but there were no strong relationships with grain yield. This suggested that the synergistic improvement in stalk lodging resistance and grain yield was not contradictory. Under the experiment conditions, the effect of spraying ethephon was most significant when the planting density was 90,000 plants ha⁻¹. At the time, the lodging percentage and grain yield were 12.2% and 11,137.5 kg ha⁻¹, which were decreased by 44.6% and increased by 8.0% compared with the control treatment. Scientific chemical regulation could significantly improve the stalk lodging resistance and grain yield of densely planted summer maize. Full article

In order to explore the effects of nitrapyrin (N-Serve) application on greenhouse gas emission and nitrogen (N) leaching of a waterlogged maize (Zea mays L.) field, we investigated the effects of applying nitrapyrin on soil ammonium (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) content, nitrous oxide (N₂O) fluxes, and the warming potential (GWP_N2O) in a waterlogged maize field. The design included three treatments: waterlogging treatment with only urea application (V-3WL), waterlogging treatment with urea and nitrapyrin application (V-3WL+N), and no waterlogging treatment applying only urea (CK). Our results revealed that waterlogging led to the increase of nitrate concentrations across the soil profile, thus potentially increasing N leaching and decreasing N use efficiency. The accumulated N₂O emissions increased significantly in waterlogged plots compared to control plots, and maximum N₂O emission fluxes occurred during the process of soil drying after waterlogging; this resulted in an increase in GWP_N2O and N₂O greenhouse gas intensity (GHGI_N2O) by 299% and 504%, respectively, compared to those of CK. However, nitrapyrin application was able to reduce N₂O emissions. Nitrapyrin application was also good for decreasing GWP_N2O and GHGI_N2O by 34% and 50%, respectively, compared to V-3WL. In addition, nitrapyrin application was conducive to reduce N leaching and improve N use efficiency, resulting in a yield increase by 34%, compared to that of V-3WL. The application of nitrapyrin helped to mitigate agriculture-source greenhouse effects and N leaching induced by waterlogging, and was a high N-efficient fertilizer method for a waterlogged field. Full article

Agriculture production has been found to be the most sensitive sector to climate change. Northeast China (NEC) is one of the world’s major regions for spring maize production and it has been affected by climate change due to increases in temperature and decreases in sunshine hours and precipitation levels over the past few decades. In this study, the CERES-Maize model-v4.7 was adopted to assess the impact of future climatic change on the yield of spring maize in NEC and the effect of adaptation measures in two future periods, the 2030s (2021 to 2040) and the 2050s (2041 to 2060) relative to the baseline (1986 to 2005) under RCP4.5 and RCP8.5 scenarios. The results showed that increased temperatures and the decreases in both the precipitation level and sunshine hours in the NEC at six representative sites in the 2030s and 2050s periods based on RCP4.5 and RCP8.5 climate scenarios would shorten the maize growth durations by (1–38 days) and this would result in a reduction in maize yield by (2.5–26.4%). Adaptation measures, including altered planting date, supplemental irrigation and use of cultivars with longer growth periods could offset some negative impacts of yield decrease in maize. For high-temperature-sensitive cultivars, the adoption of early planting, cultivar change and adding irrigation practices could lead to an increase in maize yield by 23.7–43.6% and these measures were shown to be effective adaptation options towards reducing yield loss from climate change. The simulation results exhibited the effective contribution of appropriate adaptation measures in eliminating the negative impact of future climate change on maize yield. Full article

Salt stress inhibited the growth of maize. B46 and NC236 were chosen as materials and NaCl concentrations (0, 55, 110, 165, and 220 mmol L⁻¹) were set. We found the activities of SOD, POD, CAT, APX, GR, MDHAR, and DHAR decreased under NaCl stress. Compared with NC236, the contents of AsA and GSH, AsA/DHA and GSH/GSSG of B46 decreased. The content of O₂⁻, H₂O₂, MDA, and EL of B46 increased. The contents of NO₃⁻ and NO₂⁻ decreased, while the content of NH₄⁺ increased under high NaCl concentration. The activities of NR and NiR decreased, while the activities of GS and GOGAT increased first and then decreased. For B46 and NC236, the maximum of NADH-GDH and NAD-GDH appeared at 165 and 110 mmol L⁻¹ NaCl concentration, respectively. Compared with B46, and the GOT and GPT activities of NC236 increased first and then decreased. With the increase of NaCl concentration, the contents of proline, soluble protein, and soluble sugar were increased. The Na⁺ content of B46 and NC236 increased, and the K⁺ content and K⁺/Na⁺ decreased. Compared with NC236, B46 had higher IAA content in leaf, higher Z + ZR content in leaf and root, and lower ABA content in leaf and root. Full article

Leaf area index (LAI) indicates the leaf area per ground surface area occupied by a crop. Various methods are used to measure LAI, which is unitless and varies according to species and environmental conditions. This experiment was carried out in three different nitrogen ranges (control, 120 kg N ha⁻¹, and 300 kg N ha⁻¹) + PK nutrient levels, with five replications used for leaf area measurement on seven different maize hybrids. Hybrids had different moisture, protein, oil, and starch contents. N (1, 2) + PK treatments had a desirable effect on protein, starch, and yield. P0217 LAI had a minimal response at these fertiliser levels. LAI for Sushi peaked at different dates between control and fertiliser treatments. This result showed that Sushi has an excellent capacity for LAI. LAI values on 15 June 2020 showed minimum average values for all hybrids, and it had a maximum average values on 23 July 2020. LAI had maximum performance between the average values treatments in Sushi, Armagnac, Loupiac, and DKC4792 on 15 June 2020. This study also provides insights for examining variably applied N doses using crop sensors and UAV remote-sensing platforms. Full article