Maize Seedlings Research Articles

Investigation of the impact of dual inoculations of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria on drought tolerance of maize grown in a compost-amended field under Mediterranean conditions.

In the current context of rapid climate change, water scarcity and soil poverty are becoming increasingly alarming, leading to growing losses of 30-50% of global agricultural production. It is imperative to find environmentally-friendly approaches for improving plant tolerance to drastic conditions, particularly in arid and semi-arid Mediterranean regions. Biostimulants based on symbiotic microbes are emerging as effective strategies for improving tolerance and agricultural productivity. This study aims to evaluate the effects of single and double inoculation of arbuscular mycorrhizal fungi (My) and plant growth-promoting bacteria (Ba) on the growth, physiological and biochemical traits of maize crop grown in compost (Co) amended soil under two irrigation regimes: well-watered (WW: 100% of crop evapotranspiration [ETc]) and drought-stressed (DS: 50% ETc) using drip irrigation system. Reducing irrigation to 50% reduced shoot dry weight (SDW), root dry weight (RDW), 1,000-grains weight (TGW) and grain yield (Y). However, Ba alone increased SDW by 63%, while CoMyBa improved RDW, TGW and Y by 197, 43 and 175%, respectively compared with the control under DS conditions. Dual inoculation boosted root colonization intensity, normalized difference vegetation index (NDVI), total chlorophyll and leaf area of maize seedlings in compost-amended soil, compared to the controls. The application of Ba significantly reduced hydrogen peroxide and malondialdehyde by 46%, in maize seedlings grown in compost-amended soil, compared to the controls under DS. Our results indicated that My and Ba significantly boost the ability of maize to tolerate drought by improving water supply and physiology and stimulating the accumulation of organic and inorganic osmolytes, as well as improving the properties of soils such as cation exchange capacity particularly amended by Co. The dual inoculations were the most effective and represent an environmentally-friendly and relatively inexpensive approach to optimizing agricultural production and soil restoration programs in Mediterranean regions.

Intercropping of tobacco and maize at seedling stage promotes crop growth through manipulating rhizosphere microenvironment.

Changes in the rhizosphere microbiome and metabolites resulting from crop intercropping can significantly enhance crop growth. While there has been an increasing number of studies on various crop combinations, research on the intercropping of tobacco and maize at seedling stage remains limited. This study is the first to explore rhizosphere effects of intercropping between tobacco and maize seedling stages, we analyzed the nitrogen, phosphorus and potassium nutrients in the soil, and revealed the important effects on soil microbial community composition and metabolite profiles, thereby regulating crop growth and improving soil balance. Compared with mono-cropping, intercropping increased the biomass of the two crops and promoted the nutrient absorption of nitrogen, phosphorus and potassium. Under intercropping conditions, the activities of sucrase, catalase and nitrate reductase in tobacco rhizosphere soil and the content of available potassium, the activities of nitrate reductase and acid phosphatase in maize rhizosphere soil were significantly increasing. Rhizosphere soil bacterial and fungal communities such as Sphingomonas, Massilia, Humicola and Penicillium respond differently to crop planting patterns, and soil dominant microbial communities are regulated by environmental factors such as pH, Organic Matter, Available Potassium, Nitrate Reductase, and Urease Enzyme. Network analysis showed that soil microbial communities were more complex after intercropping, and the reciprocal relationship between bacteria and fungi was enhanced. The difference of metabolites in soil between intercropping and monocropping system was mainly concentrated in galactose metabolism, starch and sucrose metabolism pathway, and the content of carbohydrate metabolites was significantly higher than that of monocropping soil. Key metabolites such as D-Sucrose, D-Fructose-6-Phosphate, D-Glucose-1-Phosphatel significantly influence the composition of dominant microbial communities such as Sphingomonas and Penicillium. This study explained the effects of intercropping between flue-cured tobacco and maize on the content of soil metabolites and soil microbial composition in rhizosphere soil, and deepened the understanding that intercropping system can improve the growth of flue-cured crops seedlings through rhizosphere effects.

Physiological Parameters and Transcriptomic Levels Reveal the Response Mechanism of Maize to Deep Sowing and the Mechanism of Exogenous MeJA to Alleviate Deep Sowing Stress

Deep sowing, as a method to mitigate drought and preserve soil moisture and seedlings, can effectively mitigate the adverse effects of drought stress on seedling growth. The elongation of the hypocotyl plays an important role in the emergence of maize seeds from deep-sowing stress. This study was designed to explore the function of exogenous methyl jasmonate (MeJA) in the growth of the maize mesocotyl and to examine its regulatory network. The results showed that the addition of a 1.5 μ mol L−1 MeJA treatment significantly increased the mesocotyl length (MES), mesocotyl and coleoptile length (MESCOL), and seedling length (SDL) of maize seedlings. Transcriptome analysis showed that exogenous MeJA can alleviate maize deep-sowing stress, and the differentially expressed genes (DEGs) mainly include ornithine decarboxylase, terpene synthase 7, ethylene responsive transcription factor 11, and so on. In addition, candidate genes that may regulate the length of maize hypocotyls were screened by Weighted Gene Co-expression Network Analysis (WGCNA). These genes may be involved in the growth of maize hypocotyls through transcriptional regulation, histones, ubiquitin protease, protein binding, and chlorophyll biosynthesis and play an important role in maize deep-sowing tolerance. Our research findings may provide a theoretical basis for determining the tolerance of maize to deep-sowing stress and the mechanism of exogenous hormone regulation of deep-sowing stress.

Crosstalk of methylglyoxal and calcium signaling in maize (Zea mays L.) thermotolerance through methylglyoxal-scavenging system

Methylglyoxal (MG) and calcium ion (Ca2+) can increase multiple-stress tolerance including plant thermotolerance. However, whether crosstalk of MG and Ca2+ exists in the formation of maize thermotolerance and underlying mechanism still remain elusive. In this paper, maize seedlings were irrigated with MG and calcium chloride alone or in combination, and then exposed to heat stress (HS). The results manifested that, compared with the survival percentage (SP, 45.3%) of the control seedlings, the SP of MG and Ca2+ alone or in combination was increased to 72.4%, 74.2%, and 83.4% under HS conditions, indicating that Ca2+ and MG alone or in combination could upraise seedling thermotolerance. Also, the MG-upraised SP was separately weakened to 42.2%, 40.3%, 52.1%, and 39.4% by Ca2+ chelator (ethylene glycol tetraacetic acid, EGTA), plasma membrane Ca2+ channel blocker (lanthanum chloride, LaCl3), intracellular Ca2+ channel blocker (neomycin, NEC), and calmodulin (CaM) antagonist (trifluoperazine, TFP). However, significant effect of MG scavengers N-acetylcysteine (NAC) and aminoguanidine (AG) on Ca2+-induced thermotolerance was not observed. Similarly, an endogenous Ca2+ level in seedlings was increased by exogenous MG under non-HS and HS conditions, while exogenous Ca2+ had no significant effect on endogenous MG. These data implied that Ca2+ signaling, at least partly, mediated MG-upraised thermotolerance in maize seedlings. Moreover, the activity and gene expression of glyoxalase system (glyoxalase I, glyoxalase II, and glyoxalase III) and non-glyoxalase system (MG reductase, aldehyde reductase, aldo-keto reductase, and lactate dehydrogenase) were up-regulated to a certain extent by Ca2+ and MG alone in seedlings under non-HS and HS conditions. The up-regulated MG-scavenging system by MG was enhanced by Ca2+, while impaired by EGTA, LaCl3, NEC, or TFP. These data suggest that the crosstalk of MG and Ca2+ signaling in maize thermotolerance through MG-scavenging system. These findings provided a theoretical basis for breeding climate-resilient maize crop and developing smart agriculture.

Drought and rewatering practices improve adaptability of seedling maize to drought stress by a super-compensate effect

Periodic drought adversely affects the growth and yield of summer crops in the Huang-Huai-Hai Plain. Drought-rewatering practice as one of the important agronomic measures to improve crop drought resistance. A field experiment was conducted to investigate practice physiological, biochemical, and molecular responses of maize seedling after two rounds of repeated drought and rewatering treatments. The results demonstrated that rewatering following repeated drought events had a compensatory effect on the photosynthetic rate (Pn) and on osmotic and antioxidant regulation. Specifically, the Pn and stomatal conductance (Gs) increased by 10.12% and 5.61%, respectively, compared to the control (CK) during the second round of treatment. Additionally, soluble protein (sPro) and proline (Pro) content rose significantly, with increases of 26.12% and 343.49% observed on day 5 of the second round, leading to a gradual reduction in leaf water content and osmosis. Following drought exposure, the activities of superoxide dismutase (SOD) and peroxidase (POD) contributed to the decreased levels of malondialdehyde (MDA), with both enzymes recovering during rewatering. In contrast, plant height, leaf area, and biomass were significantly reduced in the CK group. Notably, root length increased by 21.05% after the drought-rewatering practice, enhancing the maize seedlings' ability to adapt to drought stress. Overall, maize seedlings exhibited enhanced adaptability to drought conditions following two cycles of drought-rewatering treatments.

Acetone O-(2-naphthylsulfonyl) oxime alleviates the toxic effects of cadmium in maize seedlings by increasing the phenolic substance content and antioxidant system activity

The absorption of cadmium by plants largely depends on cadmium contamination in the soil. The development of phytomining and phytoremediation methods to clean cadmium-contaminated ecosystems is an urgent issue that needs to be solved. Therefore, the role of exogenous O-(2-naphthylsulfonyl)oxime (ANSO) to maize seedlings under cadmium stress was tested. The results showed that when ANSO+cadmium application was compared to cadmium, the cadmium content increased by 7.8 times, while the abscisic acid content decreased. Under cadmium stress, ANSO application did not change the relative water content, but increased the chlorophyll content. While carotenoid content increased with cadmium application, it increased further with ANSO+cadmium application. As a result of the positive effects of ANSO application on the antioxidant system under cadmium stress, hydrogen peroxide content, lipid peroxidation and proline content decreased. ANSO application under cadmium stress increased the phenolic substance content. This study shows that exogenous ANSO makes significant contributions to the protection of maize seedlings despite being under cadmium stress. It also provides important references to the fact that despite stress, the cadmium chelation mechanisms of seedlings continue to work actively to accumulate cadmium in tissues, and it has deep implications for the remediation of cadmium-polluted soils.

Identification of the fructose 1,6-bisphosphate aldolase (FBA) family genes in maize and analysis of the phosphorylation regulation of ZmFBA8

Fructose 1,6-bisphosphate aldolase (FBA) is a class of aldolase that functions as enzyme participating in carbohydrate metabolism of the Calvin-Benson cycle, gluconeogenesis, and glycolysis, and also as non-enzymatic protein involving in protein binding, gene transcription, signal transduction. FBAs have been identified in a few plant species, however, limited information is known regarding FBA family genes, their biological functions and posttranslational regulations in maize (Zea mays). In this study, nine class I FBAs (ZmFBA1 to ZmFBA9) and one class II FBA (ZmFBA10) in maize were identified. Phosphoproteomic analysis further revealed that multiple ZmFBAs were phosphorylated. We showed that phosphorylation at Ser32 in ZmFBA8 inhibited its FBP binding and enzyme activity. Loss of ZmFBA8 function reduced the growth of maize seedlings. Our results suggest that the phosphorylation is an important regulatory mechanism of ZmFBA8 function.

ZmbZIP27 regulates nitrogen-mediated leaf angle by modulating lignin deposition in maize

In grain crops such as maize (Zea mays), leaf angle (LA) is a key agronomic trait affecting light interception and thus planting density and yield. Nitrogen (N) affects LA in plants, but we lack a good understanding of how N regulates LA. Here, we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings. In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles. Under N-sufficient conditions, transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type (WT). By contrast, zmbzip27ems mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT. Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field. We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528. ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize. Taken together, these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

Alleviation of Drought Stress in Zea Mays Seeding by Extracellular Polysaccharides Produced by Azotobacter

Azotobacter bacteria are Gram-negative, rod-shaped soil bacteria that can fix atmospheric nitrogen and promote plant growth. They are known to produce exopolysaccharides (EPS), which can help plants to retain water and tolerate drought stress. In this study, 20 Azotobacter isolates were isolated from dry and semi-dry soil samples. The isolates were characterized morphologically and microscopically and tested for their tolerance to drought using PEG6000 at concentrations of 0%, 5%, 10%, 15%, 20%, and 25%. They were also tested for their ability to produce EPS. The isolates that were most tolerant to drought and produced the most EPS were used as biofertilizers to improve the drought tolerance of maize seedlings. The seedlings were irrigated every 24, 48, or 72 hours. The results showed that the biofertilizers containing the two most drought-tolerant and EPS-producing Azotobacter isolates (Azotobacter 1 and Azotobacter 2) significantly improved the germination rate, dry weight, stress tolerance index, chlorophyll stability, and membrane damage index of the maize seedlings.

Interactions between Brassinosteroids and Strigolactones in Alleviating Salt Stress in Maize.

Exogenous brassinolide (BR) and strigolactones (SLs) play an important role in alleviating salt stress in maize. We studied the morphological and physiological responses of the salt-sensitive genotype PH4CV and salt-tolerant genotype Zheng58 to BR (1.65 nM), SL (1 µM), and BS (1.65 nM BR + 1 µM SL) under salt stress. Phenotypic analysis showed that salt stress significantly inhibited the growth of maize seedlings and significantly increased the content of Na+ in the roots. Exogenous hormones increased oxidase activity and decreased Na+ content in the roots and mitigated salt stress. Transcriptome analysis showed that the interaction of BR and SL is involved in photosynthesis-antenna proteins, the TCA cycle, and plant hormone signal transduction pathways. This interaction influences the expression of chlorophyll a/b-binding protein and glucose-6-phosphate isomerase 1 chloroplastic, and aconitase genes are affected. Furthermore, the application of exogenous hormones regulates the expression of genes associated with the signaling pathways of cytokinin (CK), gibberellins (GA), auxin (IAA), brassinosteroid (BR), abscisic acid (ABA), and jasmonic acid (JA). Additionally, exogenous hormones inhibit the expression of the AKT2/3 genes, which are responsible for regulating ion transduction and potassium ion influx. Four candidate genes that may regulate the seedling length of maize were screened out through WGCNA. Respective KOG notes concerned inorganic ion transport and metabolism, signal transduction mechanisms, energy production and conversion, and amino acid transport and metabolism. The findings of this study provide a foundation for the proposition that BR and SL can be employed to regulate salt stress alleviation in maize.

The Detection of Maize Seedling Quality from UAV Images Based on Deep Learning and Voronoi Diagram Algorithms

Assessing the quality of maize seedlings is crucial for field management and germplasm evaluation. Traditional methods for evaluating seedling quality mainly rely on manual field surveys, which are not only inefficient but also highly subjective, while large-scale satellite detection often lacks sufficient accuracy. To address these issues, this study proposes an innovative approach that combines the YOLO v8 object detection algorithm with Voronoi spatial analysis to rapidly evaluate maize seedling quality based on high-resolution drone imagery. The YOLO v8 model provides the maize coordinates, which are then used for Voronoi segmentation of the field after applying the Convex Hull difference method. From the generated Voronoi diagram, three key indicators are extracted: Voronoi Polygon Uniformity Index (VPUI), missing seedling rate, and repeated seedling rate to comprehensively evaluate maize seedling quality. The results show that this method effectively extracts the VPUI, missing seedling rate, and repeated seedling rate of maize in the target area. Compared to the traditional plant spacing variation coefficient, VPUI performs better in representing seedling uniformity. Additionally, the R2 for the estimated missing seedling rate and replanting rate based on the Voronoi method were 0.773 and 0.940, respectively. Compared to using the plant spacing method, the R2 increased by 0.09 and 0.544, respectively. The maize seedling quality evaluation method proposed in this study provides technical support for precision maize planting management and is of great significance for improving agricultural production efficiency and reducing labor costs.

Effects of Various Levels of Water Stress on Morpho-Physiological Traits and Spectral Reflectance of Maize at Seedling Growth Stage

Water stress (drought and waterlogging) is one highly important factor affecting food security in China. Investigating the effects of soil moisture stress on the morphological and physiological characteristics of maize seedlings is crucial for ensuring food production. The use of spectral monitoring to observe crop phenotypic traits and assess crop health has become a focal point in field crop research. However, studies exploring the contribution of crop phenotypic and physiological data to the Normalized Difference Vegetation Index (NDVI) are still limited. In this study, a 35-day pot experiment was conducted with seven soil moisture gradients: 50%, 60%, 70%, 80% (control group, CK), 90%, 100%, and 110% treatment. In order to investigate the effects of soil moisture stress on seedling phenotypes, antioxidant enzyme activities, and NDVI, an ASD FieldSpec 4 Hi-Res NG portable spectrometer was used to collect spectral data from maize (Zea mays L. B73) leaves. The contributions of maize phenotypic and physiological traits to NDVI were also examined. The results indicated that (1) the 50% and 110% treatments significantly affected maize seedling phenotypes compared to the CK group; (2) the activities of superoxide dismutase (SOD) and peroxidase (POD) in the leaves increased under water stress, while the activities of glutathione peroxidase (GSH-PX) and ascorbate peroxidase (APX) decreased; (3) soil moisture stress (drought and waterlogging) reduced photosynthetic pigments, chlorophyll content (SPAD), and NDVI, with inhibitory effects intensifying as the stress level increased; (4) Redundancy analysis showed that antioxidant enzymes explained 69.87% of the variation in seedling height, leaf area, and NDVI. Soil moisture stress, chlorophyll, and SPAD explained 58.14% of the variation in these parameters. The results demonstrated that maize seedlings were highly sensitive to soil moisture changes, and the SPAD value contributed significantly to NDVI (p < 0.01). This study provides valuable insights for future research in precision agriculture management

Stomata: gatekeepers of uptake and defense signaling by green leaf volatiles in maize.

Plants adapt to balance growth-defense tradeoffs in response to both biotic and abiotic stresses. Green leaf volatiles (GLVs) are released after biotic and abiotic stresses and function as damage-associated signals in plants. Although, GLVs enter plants primarily through stomata, the role of stomatal regulation on the kinetics of GLV uptake remains largely unknown. Here, we illustrate the effect of stomatal closure on the timing and magnitude of GLV uptake. We closed stomata by either exposing maize (Zea mays) plants to darkness or applying abscisic acid, a phytohormone that closes the stomata in light. Then, we exposed maize seedlings to (Z)-3-hexen-1-ol and compared its dynamic uptake under different stomatal conditions. Additionally, we used (E)-3-hexen-1-ol, an isomer of (Z)-3-hexen-1-ol not made by maize, to exclude the role of internal GLVs in our assays. We demonstrate that closed stomata effectively prevent GLV entry into exposed plants, even at high concentrations. Furthermore, our findings indicate that reduced GLV uptake impairs GLV-driven induction of biosynthesis of sesquiterpenes, a group of GLV-inducible secondary metabolites, with or without herbivory. These results elucidate how stomata regulate the perception of GLV signals, thereby dramatically changing the plant responses to herbivory, particularly under water stress or dark conditions.

Exogenous Melatonin Alleviates NaCl Injury by Influencing Stomatal Morphology, Photosynthetic Performance, and Antioxidant Balance in Maize.

Maize (Zea mays L.) is sensitive to salt stress, especially during seed germination and seedling morphogenesis, which limits maize growth and productivity formation. As a novel recognized plant hormone, melatonin (MT) participates in multiple growth and developmental processes and mediates biotic/abiotic stress responses, yet the effects of salt stress on maize seedlings remain unclear. Herein, we investigated the effects of 150 μM exogenous MT on multiple phenotypes and physiologic metabolisms in three-leaf seedlings across eight maize inbred lines under 180 mM NaCl salt stress, including growth parameters, stomatal morphology, photosynthetic metabolisms, antioxidant enzyme activities, and reactive oxygen species (ROS). Meanwhile, the six gene expression levels controlling antioxidant enzyme activities and photosynthetic pigment biosynthesis in two materials with contrasting salt resistance were examined for all treatments to explore the possible molecular mechanism of exogenous MT alleviating salt injury in maize. The results showed that 150 μM exogenous MT application protected membrane integrity and reduced ROS accumulation by activating the antioxidant system in leaves of maize seedlings under salt stress, their relative conductivity and H2O2 level average reduced by 20.91% and 17.22%, while the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) averaged increased by 13.90%, 17.02%, 22.00%, and 14.24% relative to salt stress alone. The improvement of stomatal size and the deposition of photosynthetic pigments were more favorable to enhancing photosynthesis in leaves when these seedlings treated with MT application under salt stress, their stomatal size, chlorophyll content, and net photosynthetic rate averaged increased by 11.60%, 19.64%, and 27.62%. Additionally, Gene expression analysis showed that MT stimulation significantly increased the expression of antioxidant enzyme genes (Zm00001d009990, Zm00001d047479, Zm00001d014848, and Zm00001d007234) and photosynthetic pigment biosynthesis genes (Zm00001d011819 and Zm00001d017766) under salt stress. At the same time, 150 μM MT significantly promoted seedling growth and biomass accumulation. In conclusion, our study may unravel crucial evidence of the role of MT in maize seedlings against salt stress, which can provide a novel strategy for improving maize salt stress resistance.

Respuesta morfológica de plántulas de maíz nativo (Zea mays L.) a ambientes contrastantes de nitrógeno

Nitrogen plays a vital role in plant metabolism, influencing growth and development, particularly in crops like maize (Zea mays L.). This study aimed to evaluate the morphological response of maize seedlings to different nitrogen levels. The design was a completely randomized factorial arrangement of 4 x 2, involving four maize cultivars and two nitrogen levels.The variety Sb 302 Berentsen and three native varieties originating from Tecamachalco, Puebla, Mexico were studied. For a period of 14, 21, 28 and 35 days, seedlings were grown in nutrient solution with 10 % and 100 % nitrogen levels under hydroponic conditions. The results revealed significant variability in seedling morphology, particularly in root architecture and dry weight, between the 10 % and 100 % nitrogen treatments. High coefficients of variation were observed in the lengths of crown and seminal roots, alongside significant correlations between root and seedling dry weights at both nitrogen levels. Additionally, a strong correlation was found between root length and number under the 10 % nitrogen treatment. The results highlight the critical role of nitrogen in maize seedling development and the interaction between nitrogen concentration and maize variety, particularly in primary root length. The study improves understanding of nitrogen's role in optimizing maize growth and suggests strategies to enhance nitrogen use efficiency across different maize varieties. Keywords: cereals, nitrogen use efficiency, root architecture, native varieties.

The transcription factor ZmbHLH105 confers cadmium tolerance by promoting abscisic acid biosynthesis in maize

Cadmium (Cd), a highly toxic heavy metal, profoundly impacts crop productivity. The bHLH-type transcription factors regulate plant stress responses, yet their involvement in maize's Cd stress response remains unclear. Here, we studied ZmbHLH105, a maize bHLH gene induced by Cd exposure. Overexpression of ZmbHLH105 in maize seedlings, which were treated with 1.0 mM CdCl2 for 7 days, increased endogenous ABA levels, decreased Cd accumulation, and enhanced Cd stress tolerance. ZmbHLH105 directly bound to promoter regions of two key ABA biosynthesis genes ZmNCED1/2, activating their transcription, thus boosting ABA levels and Cd tolerance. ZmbHLH105-overexpression promoted lignin synthesis, while ZmbHLH105-RNAi attenuated this effect. Exogenous ABA supplementation increased lignin content in Cd-stressed maize roots, suggesting ZmbHLH105-mediated Cd tolerance involves ABA-induced lignin deposition and cell wall thickening. Moreover, Cd transport-related gene expression was suppressed in ZmbHLH105 overexpression lines. Our findings demonstrate that ZmbHLH105 decreases Cd accumulation, improving Cd tolerance by enhancing ABA biosynthesis, increasing lignin deposition, thickening cell walls, and inhibiting Cd absorption in maize roots. This study unveils ZmbHLH105's mechanisms in Cd tolerance, highlighting its potential in breeding low Cd-accumulating crops for food and environment safety.

The Transcription Factor ZmMYB56 Regulates High CO2-Induced Stomatal Closure in Maize Seedlings by Regulating ZmHLT1 Expression.

Stomata are channels through which plants exchange H2O and CO2 with the external environment. The regulation of stomatal movement has significant impacts on plant growth, development and stress adaptation. Here, we present a maize R2R3 -MYB transcription factor, ZmMYB56, which regulates high CO2-induced stomatal closure in maize seedlings. ZmMYB56 is highly expressed in stomatal guard cells and is negatively regulated by CO2 and HCO3 -. Loss of ZmMYB56 function leads to insensitivity to high CO2. As a transcription factor, ZmMYB56 binds to a cis-acting element in the ZmHLT1 promoter and regulates its expression. ZmHLT1 plays a key role in CO2- induced maize stomatal movement, and its absence causes a severe weakening of maize's response to ambient CO2. ZmHLT1 expression is negatively regulated by bicarbonate, which does not occur in Zmmyb56 mutants, highlighting the significance of this regulatory relationship in plant responses to CO2 and HCO3 -. Taken together, these results show that ZmMYB56-regulated ZmHLT1 expression is important for high CO2-induced stomatal closure in maize. Our findings provide insight into genetic pathways that could be manipulated to improve maize growth and stress tolerance, especially under increasing atmospheric CO2 concentrations.

Bacillus cereus CGMCC 1.60196: a promising bacterial inoculant isolated from biological soil crusts for maize growth enhancement.

Soil microbial inoculants are widely recognized as an environmentally friendly strategy for promoting crop growth and increasing productivity. However, research on utilizing the microbial resources from desert biological soil crusts to enhance crop growth remains relatively unexplored. In the present work, a bacterial strain designated AC1-8 with high levels of amylase, protease, and cellulase activity was isolated from cyanobacterial crusts of the Tengger Desert and identified as Bacillus cereus (CGMCC 1.60196). The refinement of the fermentation parameters of B. cereus CGMCC 1.60196 determined that the most effective medium for biomass production was composed of 5 g/L glucose, 22 g/L yeast extract and 15 g/L MgSO4, and the optimal culture conditions were pH 6.0, temperature 37°C, inoculation quantity 3% and agitation speed 240 rpm. Furthermore, the utilization of B. cereus CGMCC 1.60196 has resulted in substantial improvements in various growth parameters of maize seedlings, including shoot length, shoot fresh and dry weights, root fresh and dry weights, and the contents of chlorophyll a, chlorophyll b, and total chlorophyll. The most pronounced growth promotion was observed at an application concentration of 1 × 109 CFU/m2. These results suggest that the novel B. cereus strain, isolated from cyanobacterial crusts, can be regarded as an exemplary biological agent for soil improvement, capable of enhancing soil conditions, promoting crop cultivation and supporting food production.

Alleviation of salt stress on Zea mays L. plant by PGPR isolates as an effective sustainable strategy

Among the major constraints for the production of economic crops, such as maize, is salinity. Plenty of research has suggested the use of various strains of plant growth-promoting rhizobacteria (PGPR) as a sustainable approach to improve plant tolerance to salinity. Nonetheless, the exploration of the rhizosphere in Egyptian agricultural lands with salt affected soil remains incomplete. In this research, two newly isolated local bacterial species were finally selected and identified as Alcaligenes sp. strains. E1 (BS-45) and E2 (BS-57). IAA production by both isolates was confirmed by TLC. Several bioactive metabolites were identified in Alcaligenes sp. E1 and E2 by gas chromatography-mass spectroscopy (GC-MS). These include 9,12,15-octadecatrienoic acid, 2,3-bis [(trimethylsilyl)oxy] propyl ester, (z,z,z), 2 (1H)-Naphthalenone, octahydro-1-methyl-1-(2-propenyl)-, (1à,4aá,8aà), dodecane and isopulegol which have a defensive role against biotic and abiotic stress of the plant. Interestingly, the selected bacteria Alcaligenes sp. E1 and E2 significantly improve the overall maize growth attributes, antioxidant scavenging activities and photosynthetic pigments in maize plants grown under salt stress (150 mM NaCl) compared to the control plants as analyzed by greenhouse experiment. Therefore, this study recommends the Alcaligenes sp. strains (E1 and E2) to alleviate the negative impact of salinity on the growth and development of maize seedlings.

Evaluating the Impact of UVC Exposure on Forage Maize Seeds under Hydroponic Condition

Background: UV radiation, with shorter wavelengths than visible light, plays a pivotal role in stimulating growth processes and boosting the synthesis of beneficial compounds in plants. Moreover, it triggers morphological changes and genetic responses, shaping plants’ physical traits and adaptability. Nevertheless, a nuanced understanding is necessary as excessive UV exposure can also cause harm, underscoring the complexity of the relationship between UV radiation and plants. The study aimed to evaluate the effect of ultraviolet C (UVC) light exposure on the germination and growth of forage maize seeds under controlled conditions in an indoor crop. One sample of seeds was exposed to UVC light, while the other was not. Methods: The experiment was carried out for 14 days, with the plants subjected to mixed blue-red light, fertigation and kept at a maximum external temperature of 30°C and maximum internal temperature of 25.1°C. UVC light is applied for 10 minutes to the seeds before germination. Result: The results showed that the plants exposed to UVC light had an average growth increase of 3cm compared to those that did not receive the treatment. However, the protein content of both sets of seedlings was similar. The study suggests that further research is necessary to determine the optimal duration and distance for UVC exposure to minimize any potential negative effects on the plants. It also highlights the need to investigate the effect of UVC radiation on the nutritional content of hydroponic crops to ensure that the increased growth does not come at the expense of nutritional quality. The experiment was carried out in Medellin, Colombia, with a maximum solar radiation of 1000 W/m2 and an altitude of 1500 meters. Overall, the study provides evidence that UVC radiation can enhance the growth of hydroponic maize seedlings, but more research is needed to fully understand its effects. At the end, there is an improvement in the growth of forage corn in seeds that have been subjected to UVC light compared to those that have not. It is worth highlighting the need for more research on changes in nutritional components in general.