Rate Of Maize Research Articles

Effects of seed priming and foliar application of Se nanoparticles in the germination, seedling growth, and reproductive stage of tomato and maize

Sustainable approaches, such as nanotechnology-based strategies, are being researched to increase the productivity of crops. This study aimed to evaluate the effects of nanopriming with selenium nanoparticles (Se NPs) for tomato (Solanum lycopersicum) and maize (Zea mays). Additionally, the impact of Se NPs delivered through a foliar application during the reproductive stage of both crops was evaluated. The results showed that Se NPs inhibited the germination rate in maize by up to 100 % but increased the germination rate and vigor index in tomato by 50 and 208 %, respectively (at 10 ppm of Se NPs). Chlorophyll and proline contents were significantly affected in both crops (tomato and maize), suggesting that Se NPs activated the stress defense systems. In contrast, the foliar application of Se NPs on tomato in the reproductive stage increased the length and width of the stem by 10.8 and 4.3 %, respectively. The chlorophyll content increased by 30.8 % at 10 ppm of Se NPs. Additionally, the proline content of reproductive maize plants increased by up to 1303.6 %, indicating significant stressful conditions caused by the exogenous delivery of Se NPs. These results suggested that nanopriming seeds and foliar application of Se NPs positively impacted tomato. Conversely, the germination of maize seeds and the development of reproductive plants were severely inhibited by Se NPs.

Yield loss of inferior crop species and its physiological mechanism in a semiarid cereal-legume intercropping system

Reducing the yield loss of inferior crop species is crucial for improving the production of intercropping systems, particularly in drought-prone regions. Yet, the physiological mechanism of yield loss caused by interspecific competition in response to soil water availability is unclear. A two-year (2018–2019) field experiment was conducted to explore the impacts of interspecific competition on yield formation of the inferior crop in the maize-faba bean intercropping system with and without plastic film mulching in a semiarid rainfed region. The plant-water relation, and yield formation in association with nitrogen (N) remobilization were determined and compared. Results indicated that the land equivalent ratio of the intercropping system was greater than 1, regardless of whether treated with plastic mulching. However, the net effect of the intercropping system was significantly greater than 0 only under plastic mulching. Intercropping with faba beans prolonged the anthesis-silking interval of maize by 93.7% (p < 0.05) and the bald tip length by 56.2% (p < 0.05). This trend resulted in insufficient pollination of tassels and an increased kernel abortion rate in maize (p < 0.05). Moreover, the amount of dry matter and N transfer to grain in vegetative organs decreased by 34.0% and 23.2% (p < 0.05), respectively. Physiologically, this brought about yield loss in the intercropped maize. Water competition from faba bean significantly reduced the soil water availability in the intercropped maize strips, regardless of whether treated with plastic mulching. However, plastic mulching alleviated the competition for water between faba bean and maize, and thus kernel abortion in maize was significantly reduced. Our findings reveal the physiological mechanism of yield loss in intercropped inferior species, by connecting kernel formation and remobilization function, in the semi-arid and rainfed intercropping systems. Specific water or nutrient management strategies might be needed for inferior crops to further improve the total productivity of cereal-legume intercropping system in drought-prone environments.

C4 maize and sorghum are more sensitive to rapid dehydration than C3 wheat and sunflower.

The high productive potential, heat resilience, and greater water use efficiency of C4 over C3 plants attract considerable interest in the face of global warming and increasing population, but C4 plants are often sensitive to dehydration, questioning the feasibility of their wider adoption. To resolve the primary effect of dehydration from slower from secondary leaf responses originating within leaves to combat stress, we conducted an innovative dehydration experiment. Four crops grown in hydroponics were forced to a rapid yet controlled decrease in leaf water potential by progressively raising roots of out of the solution while measuring leaf gas exchange. We show that, under rapid dehydration, assimilation decreased more steeply in C4 maize and sorghum than in C3 wheat and sunflower. This reduction was due to a rise of nonstomatal limitation at triple the rate in maize and sorghum than in wheat and sunflower. Rapid reductions in assimilation were previously measured in numerous C4 species across both laboratory and natural conditions. Hence, we deduce that high sensitivity to rapid dehydration might stem from the disturbance of an intrinsic aspect of C4 bicellular photosynthesis. We posit that an obstruction to metabolite transport between mesophyll and bundle sheath cells could be the cause.

An Integration of Linkage Mapping and GWAS Reveals the Key Genes for Ear Shank Length in Maize

Ear shank length (ESL) has significant effects on grain yield and kernel dehydration rate in maize. Herein, linkage mapping and genome-wide association study were combined to reveal the genetic architecture of maize ESL. Sixteen quantitative trait loci (QTL) were identified in the segregation population, among which five were repeatedly detected across multiple environments. Meanwhile, 23 single nucleotide polymorphisms were associated with the ESL in the association panel, of which four were located in the QTL identified by linkage mapping and were designated as the population-common loci. A total of 42 genes residing in the linkage disequilibrium regions of these common variants and 12 of them were responsive to ear shank elongation. Of the 12 genes, five encode leucine-rich repeat receptor-like protein kinases, proline-rich proteins, and cyclin11, respectively, which were previously shown to regulate cell division, expansion, and elongation. Gene-based association analyses revealed that the variant located in Cyclin11 promoter affected the ESL among different lines. Cyclin11 showed the highest expression in the ear shank 15 days after silking among diverse tissues of maize, suggesting its role in modulating ESL. Our study contributes to the understanding of the genetic mechanism underlying maize ESL and genetic modification of maize dehydration rate and kernel yield.

Meta-QTL analysis explores the key genes, especially hormone related genes, involved in the regulation of grain water content and grain dehydration rate in maize

BackgroundLow grain water content (GWC) at harvest of maize (Zea mays L.) is essential for mechanical harvesting, transportation and storage. Grain drying rate (GDR) is a key determinant of GWC. Many quantitative trait locus (QTLs) related to GDR and GWC have been reported, however, the confidence interval (CI) of these QTLs are too large and few QTLs has been fine-mapped or even been cloned. Meta-QTL (MQTL) analysis is an effective method to integrate QTLs information in independent populations, which helps to understand the genetic structure of quantitative traits.ResultsIn this study, MQTL analysis was performed using 282 QTLs from 25 experiments related GDR and GWC. Totally, 11 and 34 MQTLs were found to be associated with GDR and GWC, respectively. The average CI of GDR and GWC MQTLs was 24.44 and 22.13 cM which reduced the 57 and 65% compared to the average QTL interval for initial GDR and GWC QTL, respectively. Finally, 1494 and 5011 candidate genes related to GDR and GWC were identified in MQTL intervals, respectively. Among these genes, there are 48 genes related to hormone metabolism.ConclusionsOur studies combined traditional QTL analyses, genome-wide association study and RNA-seq to analysis major locus for regulating GWC in maize.

Effect of Ultrasonic Induction on the Main Physiological and Biochemical Indicators and γ-Aminobutyric Acid Content of Maize during Germination.

Research on the nutrient content of cereal grains during germination is becoming a hot topic; however, studies on germinated maize are still scarce. This study aimed to provide a technical reference and theoretical basis for the development of functional maize health foods and to expand the application of ultrasonic technology in the production of germinated grains. In this study, the germination rate of maize was used as the evaluation index, and the ultrasonic frequency, ultrasonic temperature, and induction time were selected as the influencing factors in orthogonal experiments to determine the optimal process parameters for ultrasonic induction of maize germination (ultrasonic frequency of 45 kHz, ultrasonic temperature of 30 °C, and ultrasonic induction time of 30 min). Based on this process, the effects of ultrasonic induction on the main physiological, biochemical, and γ–aminobutyric acid contents of maize during germination were investigated. The results showed that the respiration of the ultrasonic treated maize was significantly enhanced during germination, resulting in a 27% increase in sprout length, as well as a 4.03% higher dry matter consumption rate, and a 2.11% higher starch consumption rate. Furthermore, the reducing sugar content of germinated maize increased by 22.83%, soluble protein content increased by 22.52%, and γ–aminobutyric acid content increased by 30.55% after ultrasonic induction treatment. Throughout the germination process, the glutamate acid decarboxylase activity of the ultrasonically treated maize was higher than that of the control group, indicating that ultrasonication can promote maize germination, accelerate the germination process, and shorten the enrichment time of γ–aminobutyric acid in germinated maize. The results of this study can be applied to the production of γ–aminobutyric acid enrichment in germinated maize.

EFFECT OF SEEDS SOAKING AND VEGETATIVE PARTS NUTRITION WITH ACIDS OF ASCORBIC, CITRIC AND HUMIC ON MAIZE GROWTH

A field experiment was carried out during two spring seasons in 2019 and 2020. This study was aimed to increase dry matter weight and crop growth rate of maize. First factor in main plots was nutrition vegetative parts with ascorbic and citric (100 mg l-1) for both of them and humic (1 ml l-1), in addition to the control treatment (spraying of vegetative parts with distilled water only). Second factor in sub-plots was seeds soaking with same acids above, as well as the control treatment (soaking the seeds with distilled water only). Randomize complete block design in split plot arrangement was used with three replications. The results showed a significant superiority of seeds soaking in humic acid for traits of number of days from planting to 75% anthesis and silking (66.4 and 66.3 day) and (72.3 and 72.3 day), plant height (194.0 and 230.8 cm), leaves area plant-1 (6969.5 and 6570.2 cm2), leaf area index (3.71 and 3.50), dry matter weight (11.6 and 12.2 ton ha-1), crop growth rate (3.0 and 3.2 g cm-2 day-1) and chlorophyll leaf content (60.2 and 69.5 SPAD) for both seasons, respectively. Effect of vegetative parts nutrition and interaction effect of both studied factors was non-significant for most traits. It can be concluded that seeds soaking in humic acid improved growth traits. It can be recommended to soak seeds of maize before planting in humic acid at concentration of 1 ml l-1.

Effects of replacement of maize with cassava stem meal on growth and haematology of african catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;, Burchell 1822) fingerling

The study investigated effects of replacing maize meal with cassava stem meal on growth performance and haematology of African catfish (Clarias gariepinus) fingerlings. Cassava stem meal (CSM) was substituted for maize at 0% (control), 25%, 50%, 75% and 100% to produce five isonitrogenous (45% CP) diets. C. gariepinus fingerlings (mean weight 3.08±0.02g) were randomly distributed into concrete tanks (0.9m3) at 10 fish/tank in triplicates and fed twice daily for 8 weeks. Results showed the highest mean weight gain (1.72±0.01g) and the best food conversion ratio (0.08±0.01) in fish fed diet containing 25% CSM which were significantly different (p&lt;0.05) from other treatments. Fish fed 100% CSM recorded the highest value for protein efficiency ratio which differed significantly (p&lt;0.05) from other treatments. The highest survival rate of (73.3±0.01%) was recorded in fish fed 50% and 100% cassava stem meal inclusion levels while the lowest (33.4±0.01%) was observed in the control diet. The haematological results showed that packed cell volume (PCV), red blood cell (RBC) and haemoglobin (Hb) were significantly different (p&lt;0.05) among treatments. There was an increase in the counts of PCV, white blood cell, Hb, mean corpuscular volume, mean corpuscular haemoglobin while mean corpuscular haemoglobin concentration remained constant in all the treatments. The study revealed that 25% substitution rate of maize with cassava stem meal would not have any adverse effect on the growth and blood parameters of catfish.&#x0D; Key words: Cassava stems meal, fish growth, nutrient utilization, haematology, C. gariepinus

Using Eight Crops to Show the Correlation between Paucity Irrigation and Yield Reduction of Al-Hussainiyah Irrigation Project in Karbala, Iraq

Efficiency of water use in irrigation field always motivates researchers to find a way which could reduce irrigation quantity and obtain approximately the same crop yields. This study estimated the relationship between the paucity irrigation with the reduction in yield for eight crops (cotton, maize, alfalfa, small grain, summer vegetable, sesame, sunflower, and palms) by using various paucity irrigation stages from evapotranspiration of crops (5, 10, 15, 20, and 25%) as an indication of all crop outgrowth using medium soil. This study selected the project of Al-Hussainiyah irrigation that lies in Karbala province, which is close to Baghdad relative to the South. Also, the project has high importance because most dwellers have used the province for agriculture and drinking purposes. These are reasons of choosing it as a case study to implement paucity irrigation strategy on most crops (eight crops) within the project. The necessary records related to this study were obtained from specialized offices in Iraq, particularly water resources and agriculture ministries. Computer programs such as CROPWAT version 8.0, statistical program SPSS statistics version 20, and table curve 2D version 5.0 are considered the software for solving this model. This model was tested for its application and sensitivity by changing paucity levels for each crop. The comparison between the available and the estimated water demand showed that the paucity in irrigation water demand was very clear during the period from February to December for the average present state of agriculture. The correlation analysis gives a result that the paucity irrigation level with yield reduction manifested that the yield reduction rate of maize recorded higher than the other crops, while cotton recorded lower yield reduction rate than the other crops during all paucity stages.

Genomic prediction of maternal haploid induction rate in maize.

Genomic prediction (GP) might be an efficient way to improve haploid induction rate (HIR) and to reduce the laborious and time-consuming task of phenotypic selection for HIR in maize (Zea mays L.). In this study, we evaluated GP accuracies for HIR and other agronomic traits of importance to inducers by independent and cross-validation. We propose the use of GP for cross prediction and parental selection in the development of new inducer breeding populations. A panel of 159 inducers from Iowa State University (ISU set) was genotyped and phenotyped for HIR and several agronomic traits. The data of an independent set of 53 inducers evaluated by the University of Hohenheim (UOH set) was used for independent validation. The HIR ranged from 0.61 to 20.74% and exhibited high heritability (0.90). High cross-validation prediction accuracy was observed for HIR (r=0.82), whereas for other traits it ranged from 0.36 (self-induction rate) to 0.74 (days to anthesis). Prediction accuracies across different sets were higher when the larger panel (ISU set) was used as a training population (r=0.54). The average HIR of the 12,561 superior predicted progenies (μSP ) ranged from 1.00-18.36% and was closely related to the corresponding midparent genomic estimated breeding value (GEBV). A predicted genetic variance (VG ) of reduced magnitude was observed in the twenty crosses with highest midparent GEBV or μSP for HIR. Our results indicate that although GP is a useful tool for parental selection, decisions about which cross combinations should be pursued need to be based on optimal trade-offs between maximizing both μSP and VG .

Integrating a genome-wide association study with transcriptomic analysis to detect genes controlling grain drying rate in maize (Zea may, L.).

Candidate genes on grain drying rate (GDR) were identified, and drying molecular mechanism of grain was explored by integrating genome-wide association with transcriptomic analysis in maize. Grain drying rate (GDR) is a key determinant of grain moisture at harvest. Here, a genome-wide association study (GWAS) of 309 inbred maize lines was used to identify single-nucleotide polymorphisms (SNPs) associated with drying rates of grain, cob and bract. Out of 217,933 SNPs, seven significant SNPs were repeatedly identified in four environments (P < 10-4). Based on genomic position of significant SNPs, six candidate genes were identified, one of which (Zm00001d047468) was verified by transcriptomic data between inbred lines with high and low GDR, indicating stable and reliable correlation with GDR. To further detect more genes correlated with GDR and explore drying molecular mechanism of grain, expression profile of all GWAS-identified genes (4941) detected from different environments, tissues and developmental stage was evaluated by transcriptomic data of six inbred lines with high or low GDR. Results revealed 162 genes exhibit up-regulated expression and another 123 down-regulated in three higher-GDR inbred lines. Based on GO enrichment, 162 up-regulated genes were significantly enriched into grain primary metabolic process, nitrogen compound metabolic process and macromolecule metabolic process (P < 0.05), which indicated grain filling imposes notable influence on GDR before and after physiological maturity. Our results lay foundation in accelerating development of higher-GDR maize germplasm through marker-assisted selection and clarifying genetic mechanism of GDR in maize.

A leucine-rich repeat-receptor-like kinase gene SbER2\u20131 from sorghum (Sorghum bicolor L.) confers drought tolerance in maize

BackgroundERECTA (ER) is a leucine-rich repeat-receptor-like kinase gene (LRR-RLK) encoding a protein isolated from Arabidopsis. Although the regulatory functions of ER genes have been widely explored in plant development and disease resistance, their roles in drought stress responses remain to be clarified.ResultsIn this study, we cloned and characterized two ER genes, SbER1–1 and SbER2–1, from the drought-tolerant model plant sorghum (Sorghum bicolor L.). Under drought stress, the two genes were expressed in the leaves and stems but not in the roots, and SbER2–1 transcript accumulation in the stem was increased. SbER2–1 was localized both on the plasma membrane and in the chloroplast. Moreover, SbER2–1 expression in Arabidopsis and maize conferred increased drought tolerance, especially in regard to water-use efficiency, increasing the net photosynthetic rate in maize under drought stress. Based on RNA-Seq analysis together with the physiological data, we conclude that the transgenic maize plants have upregulated phenylpropanoid metabolism and increased lignin accumulation under drought stress.ConclusionsOur results demonstrate that SbER2–1 plays an important role in response to drought stress. Furthermore, photosynthetic systems and phenylpropanoid metabolism are implicated in SbER2–1-mediated drought stress tolerance mechanisms. The use of genetic engineering to regulate SbER2–1 expression in plants and to breed new varieties tolerant to drought is a research field full of potential.

Physiological and gene expression studies of selected Zea mays L. and Pennisetum glaucum (L.) R. Br. genotypes to simulated drought stress condition

Drought is a major environmental stress that significantly obstructs productivity of various crops worldwide. Among several remedial methods to conquer this abiotic stress, use of resistant cultivars is most preferred. This study compares the response in selected genotypes of pearl millet and maize under a progressive drought stress conditions at specific intervals. Three genotypes (IP14599, IP14787 and LRNO3) of pearl millet recorded relatively higher water content (RWC) than the three genotypes (DTSYN11, LRN03 and LRIO1) of maize. Leaf water potential (ΨL), leaf osmotic potential (Ψπ), leaf turgor potential (Ψp) and PSII were measured in harvests to attain comparative observations. Furthermore, to correlate these results expression of three genes were measured. It was observed that Ψπ decreased over time and Ψp recorded a decrease with ΨLat a higher rate in maize compared to pearl millet. A more declining trend in maximum fluorescence (∆F/Fm′) and electron transport rate (ETR) in LRIOI, LRNO1 and DTSYN11 was recorded compared to IP14599, IP14787 and LRNO3. The study of gene CBF in leaves and roots revealed it’s responsiveness to drought in genotypes of pearl millet IP14599, LRNO3 and IP14787 while it was absent in maize genotypes LRNO1 and LRIO1, with the exception of DTSYN11. Expression of RubSc gene showed a noteworthy decline in reactive oxygen species in the genotypes IP14599, LRNO3, DTSYN11 and IP14787, while a marked increase was observed in LRNO1 and LRIO1. Likewise gene PIP2;3 were highly responsive to drought in pearl millet but not in maize, where they might support greater water transport. Overall, the results indicate remarkable activation of mRNA expression of these genes under drought stress which provides the resistance against drought.

Nitrous Oxide Emissions Increase Exponentially When Optimum Nitrogen Fertilizer Rates Are Exceeded in the North China Plain.

The IPCC assume a linear relationship between nitrogen (N) application rate and nitrous oxide (N2O) emissions in inventory reporting, however, a growing number of studies show a nonlinear relationship under specific soil-climatic conditions. In the North China plain, a global hotspot of N2O emissions, covering a land as large as Germany, the correlation between N rate and N2O emissions remains unclear. We have therefore specifically investigated the N2O response to N applications by conducting field experiments with five N rates, and high-frequency measurements of N2O emissions across contrasting climatic years. Our results showed that cumulative and yield-scaled N2O emissions both increased exponentially as N applications were raised above the optimum rate in maize ( Zea mays L.). In wheat ( Triticum aestivum L.) there was a corresponding quadratic increase in N2O emissions with the magnitude of the response in 2012-2013 distinctly larger than that in 2013-2014 owing to the effects of extreme snowfall. Existing empirical models (including the IPCC approach) of the N2O response to N rate have overestimated N2O emissions in the North China plain, even at high N rates. Our study therefore provides a new and robust analysis of the effects of fertilizer rate and climatic conditions on N2O emissions.

Responses to Potassium Application and Economic Optimum K Rate of Maize under Different Soil Indigenous K Supply

Potassium (K) is an essential macronutrient for maintaining crop productivity, but the economic benefit of K fertilizer often has been neglected. We collected a database from 60 maize field experimental sites in Northeast China between 2005 and 2012 to study the impacts of potassium (K) application rates on yield, K concentrations in grain and straw, plant K uptake, and to evaluate the economic optimum K rate (EOKR) for maize under different levels of soil indigenous K supply (IKS). The results showed that the average maize yield in Krec treatment (the recommended K rate) was highest and was 32.1% higher than that in K0 treatment (no K fertilization). Compared to K0, the application of K did not significantly increase grain K concentration, whereas it significantly increased K concentration in the straw. Plant K uptake in K150 treatment (150% of the recommended K rate) was higher than that in Krec treatment, but grain yield was lower than that in Krec treatment. Thus, the result indicates that luxury K absorption occurred in K150% treatment due to excessive K application. Thus, the application rate of K should be further optimized. Based on the modified Mitscherlich model, the average economic optimum K rate (EONR) was 135.24, 124.27, and 96.54 kg K2O/ha for the low, medium, and high levels of soil indigenous K supply (IKS), respectively. The average economic optimum yield (EOY) at a high IKS level was similar to the average yield in Krec treatment, whereas the EOKR could reduce by a K rate of 37.9–63.7 kg K2O/ha compared to Krec treatment. This study highlights the importance of K application to improve grain yield and provides a promising fertilizer recommendation method for minimizing fertilizer inputs and optimizing maize production.

Agronomic productivity, nitrogen fertilizer savings and soil organic carbon in conservation agriculture: efficient nitrogen and weed management in maize-wheat system

ABSTRACTConservation agriculture (CA) practice increases agronomic productivity and soil fertility, yet CA stimulate nitrogen (N) immobilization and weed interference during the early periods of implementation. This study focuses on efficient N management by soil testing and optical sensor (GreenSeekerTM) information; and weed management using brown manuring (Sesbania aculeata co-culture) and herbicide mixtures under CA-based maize (Zea mays L.) – wheat (Triticum aestivum L. emend Fiori & Paol) system in the Indo-Gangetic Plains. Fertilizer N application guided by the optical sensor increased grain yields of maize and wheat up to 20 and 14% (average of two years), respectively, compared to whole N application at sowing. Weed management using brown manuring in maize and herbicide mixtures in wheat increased the grain yields up to 10 and 21%, respectively, over the weedy check. The optical sensor-based N management saved up to 45 and 30 kg N ha–1 of the optimized N fertilizer rate in maize and wheat, respectively, over whole N application. Fertilizer N management coupled with brown manuring resulted in 5 and 4% higher soil organic carbon accumulation. Implementing efficient N fertilizer and weed management in the early years of CA can improve agronomic yield, fertilizer savings, and soil organic carbon content.

Response of optimum nitrogen rate in maize with legume intercropping system

A field experiment was conducted at S.V. Agricultural College farm (ANGRAU), Tirupati, India during rabi, 2009-10. The experiment was consisted of five system treatments (sole maize at 60 x 20 cm sowing, sole maize in skipped row sowing, maize in skipped row + greengram, maize in skipped row + blackgram and maize in skipped row + cluster bean) and three nitrogen doses (100, 75 and 50% recommended dose of nitrogen). The treatment combinations were laid out in factorial randomized block design with three replications. Yield attributes and grain yield of maize were maximum with sole maize at 60x20cm spacing but at par with maize + cluster bean, maize + blackgram and maize + greengram intercropping system. The lowest parameters were observed with sole maize sown in skipped rows. All the parameters were maximum with the application of 100% recommended dose of nitrogen to maize, but comparable with that of 75%. The maize equivalent yield, land equivalent ratio and benefit cost ratio were higher with maize + cluster bean intercropping as compared to other treatments. The result revealed that among the different maize intercropping systems tested, maize in skipped rows + cluster bean with 75% recommended dose of nitrogen to maize was found economically profitable.SAARC J. Agri., 15(1): 139-148 (2017)

Effects of a dark septate endophyte (DSE) on growth, cadmium content, and physiology in maize under cadmium stress.

Dark septate endophytes (DSE) are widely distributed in plant roots grown in stressful habitats, especially in heavy metal-polluted soils. But little is known about the physiological interactions between DSE and plants under heavy metal stress. In the present study, the growth, Cd content, and physiological response of Zea mays L. to a root-colonized DSE, Exophiala pisciphila, were analyzed under Cd stress (0, 5, 10, 20, and 40mg/kg) in a sand culture experiment. Under high Cd (10, 20, and 40mg/kg) stress, the DSE colonization in roots increased the maize growth, kept more Cd in roots, and decreased Cd content in shoots. The DSE colonization improved the photosynthesis and induced notable changes on phytohormones but had no significant effect on the antioxidant capability in the maize leaves. Moreover, there were significant positive correlations between the gibberellic acid (GA) content and transpiration rate, zeatin riboside (ZR) content, and photosynthetic rate in maize leaves. These results indicated that the DSE's ability to promote plant growth was related to a decrease on Cd content and the regulation on phytohormone balance and photosynthetic activities in maize leaves.

Physiological Response of Maize and Weeds in Coexistence

ABSTRACT This study aimed at evaluating the physiology of maize and weeds when living under different densities. The randomized block design with 4 replications was used. The factorial scheme 5 x 2 + 1 and 5 x 3 was adopted, for maize and weeds respectively, corresponding to weed species (Bidens pilosa, Commelina benghalensis, Urochloa brizantha, Sorghum arundinaceum and Ipomoea triloba) and infestation density (control, 15 and 30 plants m-2). Weeds were kept in coexistence with the maize hybrid DKB 390 PRO 2, with an additional treatment for maize plants absent of competition. It was kept in coexistence with maize hybrid DKB 390 PRO 2 besides an additional treatment with maize plants absent of competition. On day 45 and 60 after maize planting (DAP) physiological reviews were performed within the culture, and 38 days after weed transplanting (DAT), an infrared gas analyzer (IRGA) was used. There were physiological changes in maize due to the coexistence with weeds. On day 45 DAP, the competition, regardless of the weed species, caused less photosynthetic rate in maize coexisting with 15 plants m-2; the stomatal conductance was lower in both densities. On day 60 DAP, maize in competition with 15 and 30 plants m-2 showed lower transpiration rate. U. brizantha and S. arundinaceum showed reduction in photosynthesis and transpiration, due to increased density and coexistence with maize.

Testing the link between genome size and growth rate in maize.

Little is known about the factors driving within species Genome Size (GS) variation. GS may be shaped indirectly by natural selection on development and adaptative traits. Because GS variation is particularly pronounced in maize, we have sampled 83 maize inbred lines from three well described genetic groups adapted to contrasted climate conditions: inbreds of tropical origin, Flint inbreds grown in temperate climates, and Dent inbreds distributed in the Corn Belt. As a proxy for growth rate, we measured the Leaf Elongation Rate maximum during nighttime (LERmax) as well as GS in all inbred lines. In addition we combined available and new nucleotide polymorphism data at 29,090 sites to characterize the genetic structure of our panel. We found significant variation for both LERmax and GS among groups defined by our genetic structuring. Tropicals displayed larger GS than Flints while Dents exhibited intermediate values. LERmax followed the opposite trend with greater growth rate in Flints than in Tropicals. In other words, LERmax and GS exhibited a significantly negative correlation (r = − 0.27). However, this correlation was driven by among-group variation rather than within-group variation—it was no longer significant after controlling for structure and kinship among inbreds. Our results indicate that selection on GS may have accompanied ancient maize diffusion from its center of origin, with large DNA content excluded from temperate areas. Whether GS has been targeted by more intense selection during modern breeding within groups remains an open question.