Shoot Concentrations Research Articles

Strawberry Grown in an Indoor Vertical Farm Responds to Increased Photosynthetic Photon Flux Density When Calcium Is Supplied at Higher Concentrations

Indoor vertical farms can optimize light, temperature, humidity, and nutrient use, thus potentially maximizing crop growth and yield. However, the reported potential for enhanced crop growth and yield within these systems needs to be tempered against the understanding of the effects of this “forced growth”/optimal growth environment on “actual” plant performance to fully reap the benefits of these innovative vertical farming systems. We investigated the effect of calcium (Ca) on the production of strawberries in an indoor vertical farm system with varying photosynthetic photon flux density (PPFD). Fruit yield of plants fed with high Ca (9 meq·L−1) increased by 42.3% when the PPFD was 422 µmol·m−2·s−1; however, a subsequent increase to 572 µmol·m−2·s−1 resulted in a decline in fruit production. Plants treated with low Ca (5 meq·L−1) had a reduced yield and demonstrated no response to the PPFD. The observed increase in yield was associated with increased fruit production and total soluble solids. Plants exhibited 21.5% and 57.8% increases in the total dry weight when exposed to 422 and 572 µmol·m−2·s−1, respectively; however, Ca did not have any impact on this response. Independent of the Ca concentration, the photosynthesis rate increased by 16.1% and 22.2% when the PPFD increased to 422 and 572 µmol·m−2·s−1, respectively; however, the highest photosynthesis rate was recorded with 422 µmol·m−2·s−1 when the Ca level was 9 meq·L−1. High Ca-fed plants exhibited a reduction in Ca (−17.1%) content in their fruits when exposed to 572 µmol·m−2·s−1, which was likely caused by a dilution effect attributable to increased fruit biomass. In contrast, shoot Ca increased when plants were given high Ca when the PPFDs were 422 and 572 µmol·m−2·s−1. The Ca concentration in shoots correlated with the increasing yield, and a higher Ca concentration was associated with the increasing transpiration rate and stomatic conductance. Shoot phosphorus declined when plants were exposed to increased PPFD, and phosphorus was lower when plants were provided with 9 meq·L−1 of Ca; however, plants watered with low Ca solutions had more potassium. The shoot nitrogen content and micronutrient contents were unchanged regardless of the variations in PPFD or Ca. In summary, the favorable conditions for the cultivation of strawberry under controlled environments resulted in greater growth and fruit yield as long as Ca was provided at higher concentrations in the irrigation solutions (from 5 to 9 meq·L−1). We suggest that the higher demand of Ca that is necessary to satisfy the enhanced plant development observed in indoor farming systems may be connected to the role of Ca in the formation of new tissues, cell walls, and cell membranes.

Pseudomonas putida triggers phosphorus bioavailability and P-transporters under different phosphate regimes to enhance maize growth

The decline of available phosphorus in soil due to anthropogenic activities necessitates utilizing soil microorganisms that influence soil phosphorus levels. However, the specific mechanisms governing their interaction in Zea mays under diverse phosphate regimes remain largely unknown. The present study investigated the dynamics of phosphorus solubilization and the impact of organic acid supplementation in combination with the beneficial rhizobacterium Pseudomonas putida (RA) on maize growth under phosphorus-limiting and unavailable conditions. HPLC analysis revealed gluconic acid as the primary organic acid (OA) produced by P. putida across all three conditions (P-sufficient, P-limiting, and P-unavailable), with the highest production occurring under P-limiting conditions. The study evaluates the effects of RA, OA, and OA+RA on plant growth parameters under P-limiting and insufficient conditions, revealing significant alterations in growth and biochemical parameters (P=0.05) compared to their respective untreated controls. Additionally, plants treated with organic acids and bacterial inoculation show increased phosphorus concentrations in both roots and shoots. Gene expression analysis of key phosphorus transporter genes (PHT1, PHO1,PTF, PHF1) further supports the role of organic acids and bacterial inoculation in enhancing phosphorus uptake. In conclusion, our study affirms that the secretion of gluconic acid by RA and its plant growth-promoting properties boost phosphorus uptake and maize growth by increasing phosphorus availability and influencing the expression of phosphorus transport-related genes.

Alleviation of cadmium toxicity by improving antioxidant defense mechanism and nutrient uptake in wheat (Triticum aestivum L.) through foliar application of 24-epibrassinolide under elevated CO2.

Heavy metals like cadmium (Cd) contamination occur in conjunction with the rising CO2 threatening food security and safety. Foliar application of 24-Epibrassinolide (EBR) was found to ameliorate Cd stress and improve nutrient availability in crops. However, its role under elevated CO2 is currently unknown. Accordingly, a pot experiment was conducted in open-top chambers (CO2 at 400 and 600 μmol mol−1) to determine the protective effect of EBR on wheat plants under different Cd concentrations (0, 2, and 4mgkg-1) in soil. The foliar application of EBR significantly improved growth, biomass, photosynthesis, proline, total phenol, and total soluble protein in Cd stress treatments under elevated CO2. Simultaneously, it significantly (p≤ 0.05) increased catalase (42.89%), superoxide dismutase (26.53%), peroxidase (28.10%), and ascorbate peroxidase (61.70%) while reduced malondialdehyde (35.53%), hydrogen peroxide (19.94%), and electrolyte leakage (23.55%) under elevated CO2 compared to ambient CO2 conditions. Furthermore, EBR and elevated CO2 interactively showed a maximum reduction in Cd concentrations and accumulation in the wheat roots (39.74,41.63%), shoots (46.83,44.87%), and grains (27.52,29.06%) respectively. Elevated CO2 and Cd stress interactively showed a significant reduction in nutrient content. Conversely, the EBR application recovered and significantly increased calcium, magnesium, iron, zinc, and copper content in wheat roots, shoots, and grains. Our findings inferred that EBR foliar application reduced Cd toxicity and improved plant growth and nutritional quality under elevated CO2.

Effect of different light conditions on the growth response of sugar beet to NaCl

ABSTRACT It is known that sugar beet, derived from a halophytic wild ancestor, is highly salt-tolerant and that moderate concentrations of NaCl enhance its growth. However, the mechanisms of this improved growth performance by NaCl are not fully understood. In this study, we investigated the effects of NaCl on sugar beet growth under different light conditions and examined the relationship between light-induced oxidative stress and the beneficial effects of NaCl. Sugar beet seedlings in pots filled with fertilized soil were grown with different light intensities (low: 150–250 μmol m−2s−1 or high: 600–1,000 μmol m−2s−1) and NaCl treatments (irrigation with water with or without 50 mM NaCl) for 10 days. The enhanced sugar beet growth by NaCl application was only observed in plants with high light intensity treatments. Moreover, high light intensity treatment increased the shoot concentration of malondialdehyde, an indicator of oxidative stress, while NaCl application decreased it. While there was a positive correlation between Na concentration and the compatible solute glycine betaine in the shoots and roots under both light intensities, a significant negative correlation between the concentrations of glycine betaine and malondialdehyde was found only in the shoots under high light intensity. Because it is known that glycine betaine activates antioxidant enzyme activities and reduces oxidative stress responses, glycine betaine synthesized in response to NaCl accumulation may have reduced the oxidative stress caused by high light intensity in the shoots, which may have caused the enhanced growth in sugar beet. Furthermore, the growth promotion by NaCl accumulation was accompanied by a significant decrease in NO3–N concentration, which suggested that NaCl application affects nitrogen metabolism in sugar beet.

Why can Palhinhaea cernua (lycophyte) grow closer to fumaroles in highly acidic solfatara fields?

Palhinhaea cernua, a lycophyte, and Dicranopteris linearis, a fern, are commonly observed in solfatara fields in Kyushu, Japan, but their distribution trends are different. The aim of this study was to determine why P. cernua is more abundant in areas closer to fumaroles from both a soil and plant perspective. Samples of P. cernua and D. linearis, as well as their respective growing soils, were collected, and the mineral properties, including the concentration of various mineral elements and inorganic anions and δ15N, were determined. P. cernua was better adapted to soil with lower pH, higher soluble aluminum concentrations, and poorer calcium and phosphorus concentrations than D. linearis. A positive correlation was observed between shoot nitrogen concentration and both shoot sulfur concentration and soil water-soluble sulfur concentration in P. cernua, implying the involvement of sulfur in nitrogen acquisition in P. cernua. The results also suggested that D. linearis mainly uses soil NO3-N, while P. cernua uses NH4-N, which is predominant and excessive in the solfatara fields, particularly near the fumaroles. This high preference for NH4-N in P. cernua was confirmed through a cultivation experiment. While D. linearis prefers NO3-N and distributes further from fumaroles, P. cernua may have survived in the solfatara fields by utilizing NH4-N and sulfur, which are abundant near fumaroles where competition from other plant species is minimal.

Prospects of iron solubilizing Bacillus species for improving growth and iron in maize (Zea mays L.) under axenic conditions

Iron (Fe) deficiency in calcareous soils is a significant agricultural challenge, affecting crop productivity and nutritional quality. This study aimed to isolate, characterize, and evaluate Fe solubilizing rhizobacterial isolates from maize rhizosphere in calcareous soils as potential biofertilizers. Forty bacterial isolates coded as SG1, SG2, …, SG40 were isolated and screened for siderophore production, with ten showing significant Fe solubilizing capabilities. These isolates were further assessed for phosphate solubilization and exopolysaccharides production. The selected bacterial isolates were also screened under axenic conditions for their ability to improve maize growth. The isolates SG8, SG13, SG24, SG30 and SG33 significantly enhanced growth parameters of maize. Notably, SG30 showed highest increment in shoot length (58%), root length (54%), root fresh and dry biomass (67% and 76%), SPAD value (67%), relative water contents (69%), root surface area (61%), and Fe concentration in shoots (79%) as compared to control. The biochemical characterization of these strains showed that all these strains have capability to solubilize insoluble phosphorus, produce indole-3-acetic acid (IAA), and ammonia with catalase, urease and protease activity. Molecular identification through 16s rRNA gene sequencing confirmed high similarity (99.7–100%) of the selected isolates to various Bacillus species, including B. pyramidoids, B. firmicutes, and B. cereus. The study provides a strong base for developing eco-friendly, cost-effective biofertilizers to address Fe deficiency in crops and promote sustainable agriculture.

Homocysteine S-Methyltransferase 3 Positively Regulates Cadmium Tolerance in Maize.

The increasing contamination of agricultural soils with cadmium (Cd) poses a significant threat to human health and global food security. Plants initiate a series of mechanisms to reduce Cd toxicity. However, the response of maize to Cd toxicity remains poorly understood. In this study, we identified that ZmHMT3, which encodes a homocysteine S-methyltransferases family protein, acted as a regulator of Cd tolerance in maize. Subcellular localization and in situ PCR exhibited that ZmHMT3 was localized in the cytoplasm and predominantly expressed in the phloem. Overexpression of ZmHMT3 enhanced Cd tolerance and reduced Cd concentration in both shoots and roots. In contrast, ZmHMT3 mutants attenuated Cd tolerance but did not change shoot Cd concentration. Heterologous overexpression of ZmHMT3 in rice enhanced Cd tolerance and reduced grain Cd concentration. Transcriptome analysis revealed that ZmHMT3 upregulated the expression of stress-responsive genes, especially glutathione S-transferases (GSTs) and transcription factors, including MYBs, NACs and WRKYs, and modulates the expression of different ATP-binding cassette (ABC) transporters, thereby enhancing Cd tolerance. Collectively, these findings highlight the pivotal role of ZmHMT3 in Cd tolerance and as a candidate gene for improving Cd tolerance in elite maize varieties.

Inoculation with multifunctional Bacillus sp. NEAU-DCB1-2 mitigates chromium toxicity in pakchoi (Brassica rapa ssp. chinensis) through a multi-level mechanism

Soil chromium (Cr) accumulation is escalating, severely hindering plant growth and development. Plant growth-promoting bacteria (PGPB) have shown potential in enhancing plant tolerance to heavy metals. However, the role and mechanisms of Cr(VI)-reducing PGPB strains in improving the growth of pakchoi under Cr toxicity remain unclear. This study aimed to isolate a Cr(VI)-reducing PGPB strain from Cr-contaminated soil, evaluate its effect on pakchoi growth under Cr(VI) stress, and investigate the mechanisms involved. Our findings showed that Bacillus sp. NEAU-DCB1-2 effectively reduce Cr(VI) to Cr(III) and produced indole-3-acetic acid and siderophores. Under Cr(VI) stress, inoculation with NEAU-DC1-2 significantly promoted seed germination and early growth of pakchoi. In pot experiments, NEAU-DCB1-2 significantly increased biomass accumulation, plant height, and root length of Cr(VI)-treated pakchoi seedlings, while reducing the Cr(VI) content in root, shoot and soil. Moreover, NEAU-DCB1-2 greatly increased catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase activities in seedlings under Cr(VI) stress, thereby reducing malondialdehyde content. Transcriptome analysis indicated substantial alterations in gene expression patterns after inoculation with NEAU-DCB1-2 under Cr(VI) stress. Further analyses revealed that NEAU-DCB1-2 mainly affected the responses of antioxidant system, metal chelation and transport, together with auxin, abscisic acid, and jasmonic acid signaling to Cr(VI) stress. Conclusively, the Cr(VI)-reducing PGPB strain NEAU-DCB1-2 significantly enhances the growth and Cr tolerance of pakchoi through multiple mechanisms, offering a valuable microbial resource for mitigating the adverse effects of heavy metal contamination in agricultural soils on the yield and safety of vegetable crops.

Downregulation of the rice HRS1 HOMOLOG3 transcriptional repressor gene due to N deficiency directly co-activates ammonium and phosphate transporter genes.

Rice HRS1 HOMOLOG3 (OsHHO3) acts as a transcriptional repressor of AMMONIUM TRANSPORTER1 (OsAMT1) genes in rice; thus, reduced OsHHO3 expression in nitrogen (N)-deficient environments promotes ammonium uptake. In this study, we show that OsHHO3 also functions as a repressor of a specific subset of phosphate (Pi) transporter (PT) genes involved in the uptake and root-to-shoot translocation of Pi, including OsPT2, OsPT4, and OsPHO1;1. Consistently, disruption of OsHHO3 increased Pi uptake and Pi contents in shoots and roots, while overexpression of OsHHO3 generated the opposite effects. Furthermore, phosphorus (P) deficiency slightly decreased OsHHO3 expression, upregulating a specific subset of PT genes. However, N deficiency was more effective than P deficiency in suppressing OsHHO3 expression in roots, and unlike N deficiency-dependent activation of PT genes under the control of OsHHO3, the P deficiency-dependent activation of OsAMT1 genes was minimal. Interestingly, the simultaneous deficiency of both N and P promoted the OsHHO3-regulated expression of PT genes more significantly than the deficiency of either N or P, but diminished the expression of genes regulated by OsPHR2, a master regulator of Pi starvation-responsive transcriptional activation. Phenotypic analysis revealed that the inactivation and overexpression of OsHHO3 improved and reduced plant growth, respectively, under N-deficient and P-deficient conditions. These results suggest that OsHHO3 regulates a specific subset of PT genes independently of OsPHR2-mediated regulation and plays a critical role in the adaptation to diverse N and P environments.

Growing Media pH and Nutrient Concentrations for Fostering the Propagation and Production of Lingonberry (Vaccinium vitis-idaea L.)

The lingonberry (Vaccinium vitis-idaea L.), recognized for its nutritional value and adaptability to cold climates, faces cultivation challenges, particularly in soil pH and fertility optimization. In a greenhouse study, lingonberry transplants were grown in media with pH levels of 6.5 (3:1:1 PRO-MIX BX/peat moss/perlite) and 5.2 (2:1 peat moss/perlite). Seven months post-exposure to different media pH, various fertility treatments (NPK) were tested, including a control (0–0–0), a balanced 5–5–5 kg ha−1 rate, a standard 36–24–48 kg ha−1 rate, and both higher (up to 54–36–72 kg ha−1) and lower (down to 9–6–12 kg ha−1) rates, applied every three weeks for fifteen weeks across six replications with a standard micronutrient rate. Results showed that media pH significantly affected plant height and volume, with plants at pH 6.5 growing 27% taller and larger than plants at pH 5.2. Fertility levels influenced plant volume, peaking at a moderate fertility rate (18–12–24 kg ha−1) before declining at higher rates. Interactions between pH and fertility significantly impacted shoot biomass, where higher fertility rates (above 36–24–48 kg ha−1) had a more pronounced negative effect on shoot biomass at pH 6.5 compared to pH 5.2. Root dry biomass was consistently 1.2–2.3 times greater than shoot dry biomass and less influenced by the treatments. Shoot death rates increased sharply at fertility rates above 18–12–24 kg ha−1, peaking at 21–35%. Nitrogen concentration in shoots and roots increased with higher fertilizer rates, peaking at 1.74% in the 45–30–60 kg ha−1 treatment. Fertility treatments raised growing media’s electrical conductivity (EC, 1:20 ratio), with a maximum of 1.41 dS m−1 in the 54–36–72 kg ha−1 treatment, though pH remained unchanged. Growing media nitrate levels increased with higher N rates, while ammonium levels were unaffected. Shoot death rates rose significantly with higher nitrate concentrations, particularly above 17.5 mg L−1, but showed no link to ammonium levels. Lingonberries can survive and thrive across a wide range of pH levels. These results indicate that lingonberries are resilient and low maintenance, requiring modest nutrient levels, and excessive fertilization hampers their growth.

Exogenous Brassinolide Ameliorates the Adverse Effects of Gamma Radiation Stress and Increases the Survival Rate of Rice Seedlings by Modulating Antioxidant Metabolism.

Gamma irradiation-based mutant creation is one of the most important methods for rice plant mutagenesis breeding and molecular biology research. Although median lethal dose irradiation severely damages rice seedlings, applying brassinolide (BR) can increase the survival rate of irradiated seedlings. In this study, we investigated the effects of soaking seeds in solutions containing different BR concentrations (0.001, 0.01, 0.1, 1.0, and 5.0 μmol/L) and then spraying the resulting seedlings twice with 0.1 μmol/L BR. The combined BR treatments markedly decreased the superoxide anion (O2•-), hydrogen peroxide (H2O2), and malondialdehyde contents but increased the chlorophyll content. An appropriate BR treatment of gamma-irradiated samples substantially increased the activities of the antioxidant enzymes superoxide dismutase, peroxidase, and ascorbate peroxidase as well as the proline, ascorbic acid, and glutathione contents in rice seedling shoots. The BR treatment also promoted the growth of seedlings derived from irradiated seeds and increased the shoot and root fresh and dry weights. Most notably, soaking seeds in 0.01 or 0.1 μmol/L BR solutions and then spraying seedlings twice with 0.1 μmol/L BR significantly increased the final seedling survival rate and decreased mutant loss. The study results suggest that exogenous BR treatments can protect rice seedlings from gamma irradiation stress by enhancing antioxidant metabolism.

Boron confers salt tolerance through facilitating BnaA2.HKT1-mediated root xylem Na+ unloading in rapeseed (Brassica napus L.).

Boron (B) is an important limiting factor for plant growth and yield in saline soils, but the underlying molecular mechanisms remain poorly understood. In this study, we found that appropriate B supply obviously complemented rapeseed (Brassica napus L.) growth under salinity accompanied by higher biomass production and less reactive oxygen species accumulation. Determination of Na+ content in shoots and roots indicated that B significantly repressed root-to-shoot Na+ translocation, and non-invasive micro-tests of root xylem sap demonstrated that B increased xylem Na+ unloading in the roots of rapeseed plants under salinity. Comparative transcriptomic profiling revealed that B strongly upregulated BnaHKT1s expression, especially BnaA2.HKT1, in rapeseed roots exposed to salinity. In situ hybridizations analysis showed that BnaA2.HKT1 was significantly induced in root stelar tissues by high B (HB) under salinity. Green fluorescent protein and yeast heterologous expression showed that BnaA2.HKT1 functioned as a plasma membrane-localized Na+ transporter. Knockout of BnaA2.HKT1 by CRISPR/Cas9 resulted in hypersensitive of rapeseed plants to salinity even under HB condition, with higher shoot Na+ accumulation and lower biomass production. By contrast, overexpression of BnaA2.HKT1 ameliorated salinity-induced growth inhibition under B deficiency and salinity. Overall, our results proposed that B functioned as a positive regulator for the rapeseed growth and seed production under salt stress through facilitating BnaA2.HKT1-mediated root xylem Na+ unloading. This study may also provide an alternative strategy for the improvement of crop growth and development in saline soils.

Screening Tomato Genotypes for B–Recovery and Acquisition Potential in Calcareous Soils

ABSTRACT Screening a suitable genotype is important for nutrient recovery and its acquisition potential. Twenty genotypes of tomato were studied under different doses of B-application. The indices of B use efficiencies, viz. apparent B recovery (ABR), fruit production efficiency (FPE), physiological efficiency (PE), agro-physiological efficiency (APE) and utilization efficiency ratio (UER) were worked out for tomato genotypes. The field experiment was laid out in a split-plot design for the two consecutive years, assigning three B levels (control i.e. without B application, @ 2.0 kg B ha−1 through borax and 0.25% boric acid foliar spray twice) in main plot and location-specific twenty tomato genotypes in subplots, replicated thrice. Soil applied B produced greater fruit yield than the twice foliar spray of 0.25% boric acid B. However, the tomato fruit yield was improved by 2–12% over control by soil applied B @ 2.0 kg B ha−1 through borax and twice foliar spray of B. Irrespective of genotypes, B content in fruit and shoot of tomato plant improved upon application of B. The apparent B recovery (ABR) and agronomic efficiency (AE) of B suggested that foliar application was more effective in comparison to soil application. The use efficiencies were highest in the cultivars NS–812 followed by NS–512 and B–9–2 in B-deficient calcareous soils with the application of 0.25% boric acid foliar spray twice. These genotypes could be a promising lines for breeding program for B enrichment in tomato for cultivation in B-deficient soils.

The roles of nanoparticle-enriched biochars in improving soil enzyme activities and nutrient uptake by basil plants under arsenic toxicity

Enriched biochar with improved properties and functionality can play a significant role in providing sustainable solutions for mitigating heavy metal contamination in soil. In this experiment, the effects of solid and enriched biochars (potassium-enriched biochar (BC-K), magnesium-enriched biochar (BC-Mg), both individually and combined) were examined on soil microbial and enzyme activities, as well as nutrient uptake by basil plants cultivated in a soil with three levels of arsenic (nontoxic, 50 mg As kg−1 soil, and 100 mg As kg−1 soil). Biochar-related treatments, increased soil organic matter (65–76%), while decreased availability of arsenic (6–55%) in the soil. The microbial biomass carbon (by about 123%) and soil basal respiration (by about 256%), and soil enzymatic activities (β-glucosidase, urease, alkaline phosphatase, and dehydrogenase) were enhanced by enriched biochars under arsenic toxicity. The solid and particularly enriched biochars decreased arsenic content and improved nitrogen and phosphorus contents of roots and shoots, root length, root activity, and root and shoot biomass in basil plants. Therefore, it is conceivable to suggest that enriched biochars are superior treatments for improving nutrient absorption rates and basil growth under arsenic toxicity through decreasing arsenic mobility and increasing soil microbial activities.

Nitrification inhibitor effect on manganese and phosphorus shoot concentrations in maize under different textured soils from northern Germany

High soil pH can result in Mn2+ and P deficiency, leading to crop yield losses. Therefore, supplying soil with NH4+-N fertilizer in stabilized or unstabilized form can increase soil Mn2+ availability and shoot concentration. Nitrification inhibitors (NIs) have been proposed to lower rhizosphere soil pH, thus improving plant P uptake and preventing P deficiency in soils with high pH. Thus, this study investigated whether NI-stabilized or unstabilized NH4+-N could increase Mn2+ availability in three differently-textured soils (sand, loamy sand, and silt loam) and promote Mn2+ and P shoot concentration in maize. Two greenhouse experiments were conducted to investigate the effects of applying NH4+-N fertilizer with or without the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) combined with different nitrogen (N) sources (calcium nitrate (CN), ammonium nitrate (AN), and ammonium sulphate (AS)). The measured variables were bulk and rhizosphere soil pH and Mn2+ availability, maize biomass, as well as Mn2+ and P shoot concentrations. The results indicated that DMPP-stabilized AS significantly decreased rhizosphere pH by 7.2 % in loamy sand soil texture compared with unstabilized AS. Similarly, only in the loamy sand texture, DMPP-stabilized AS increased Mn2+ availability and shoot concentration by 86 % and 47 %, respectively, relative to unstabilized AS. Furthermore, DMPP-treated AS and AN promoted P shoot concentration by 30 % and 21 % in the loamy sand and silt loam soil textures, respectively, relative to the corresponding N sources without DMPP. Conversely, DMPP did not impact the investigated variables in the sand texture for all N sources. Moreover, AN and AS increased biomass yield, Mn2+ availability, and shoot concentration by 72 %, 30 %, and 46 %, respectively, in relation to the CN fertilizer in the sand soil texture. In conclusion, this study confirmed the effectiveness of DMPP-induced rhizosphere acidification in enhancing Mn2+ and P shoot concentration in loamy sand soil textures, as well as P shoot concentration in fine-textured soil.

Improving Inoculum Production of Arbuscular Mycorrhizal Fungi in Zea mays L. Using Light-Emitting Diode (LED) Technology

A substrate-based production system is a simple and low-cost method for arbuscular mycorrhizal (AM) fungal inoculum production. However, it is time-consuming and typically yields low numbers of AM fungal spores due to several factors affecting plant growth efficiency. Our study investigated the use of light-emitting diode (LED) technology to expedite AM fungal spore production in planta. We performed experiments with Rhizophagus irregularis inoculated in maize (Zea mays L.), contrasting LED light with greenhouse (GH) conditions. Our results exhibited a significant improvement in AM fungal colonization and spore production, as well as a reduction in the production period from 120 to 90 days under the LED light condition. This was achieved using a red-and-blue light ratio of 60:40 with a total light intensity of 300 µmol m−2 s−1. The LED light treatments improved maize growth by increasing nitrogen (N) and phosphorus (P) concentrations in shoots and roots, respectively. Our gene expression analyses revealed that in AMF-inoculated plants, genes related to photosynthesis were significantly upregulated under LED light compared to the GH condition. Moreover, LED increased the expression of marker genes linked to the AM fungi-related cell cycle, indicating enhanced AM fungal growth during symbiosis. These findings advance our comprehension of LED applications in agriculture, offering promising prospects for acceleration of AM fungal spore production.

Application of different phosphatic fertilizers influences the different phosphorus fractions and morphophysiological traits of wheat in saline sodic soil

Nutrient constraints in salt-affected soils are one of the limiting factors for crop production. We investigated phosphorus (P) availability to wheat crop and its correlations with different fractions of P in salt-affected soils in response to various phosphatic fertilizer’s application. Three different types of soils having electrical conductivity of soil extract (ECe) < 4 dS m−1 and sodium adsorption ratio (SAR) < 13.2 (mmol L−1)1/2, ECe 8 dS m−1 SAR 20 (mmol L−1)1/2 and ECe 12 dS m−1 and SAR 30 (mmol L−1)1/2 were used for this experiment. Different P fertilizers viz. control, diammonium phosphate (DAP), single super phosphate (SSP) and nitrophos (NP) were applied on these soils. The doses of nitrogen, phosphorus and potassium were remained same for all the treatments. The P fractions, agronomic parameters and P-availability to plants were determined. Results indicated increase in shoot dry weight (61%) and photosynthetic rate (9%) in SSP treated soil at EC 8 dS m−1 and SAR 20 (mmol L)1/2. The total P (7.6%) in soil and respiration rate (1.9%) in plant was recorded maximum in DAP treated soil at EC 8 dS m−1 and SAR 20 (mmol L)1/2, and membrane stability index (44%) in plant shoot, extractable P (23%) in soil and P concentration (22%) in shoot were recorded maximum in SSP treated soil at EC 12 dS m−1 and SAR 30 (mmol L)1/2. It was concluded that SSP fertilizer perform better in salt-affected soil for growth and yield of wheat compared to other phosphatic fertilizers.

A multi-omics approach reveals differences in toxicity and mechanisms in rice (Oryza sativa L.) exposed to anatase or rutile TiO2 nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in agriculture, which increased the risk to soil-plant systems. Studies have demonstrated that TiO2 NPs can induce phytotoxicity. However, the toxicity mechanisms, particularly under the stress of TiO2 NPs with different crystalline forms, remain inadequately reported. In this study, we combined transcriptomics and metabolomics to analyze the toxicity mechanisms in rice (Oryza sativa L.) under the stress of anatase (AT) or rutile (RT) TiO2 NPs (50 mg/kg, 40 days). The length (decreased by 1.1-fold, p = 0.021) and malondialdehyde concentration (decreased by 1.4-fold, p = 0.0027) of rice shoots was significantly reduced after AT exposure, while no significant changes were observed following RT exposure. Antioxidant enzyme activities were significantly altered both in the AT and RT groups, indicating TiO2 NPs induced rice oxidative damage (with changes of 1.1 to 1.4-fold, p < 0.05). Additionally, compared to the control, AT exposure altered 3247 differentially expressed genes (DEGs) and 56 significantly differentially metabolites in rice (collectively involved in pyrimidine metabolism, TCA cycle, fatty acid metabolism, and amino acid metabolism). After RT exposure, 2814 DEGs and 55 significantly differentially metabolites were identified, which were collectively involved in fatty acid metabolism and amino acid metabolism. Our results indicated that AT exposure led to more pronounced changes in biological responses related to oxidative stress and had more negative effects on rice growth compared to RT exposure. These findings provide new insights into the phytotoxic mechanisms of TiO2 NPs with different crystalline forms. Based on the observed adverse effects, the study emphasizes that any form of TiO2 NPs should be used with caution in rice ecosystems. This study is the first to demonstrate that AT is more toxic than RT in paddy ecosystems, providing crucial insights into the differential impacts and toxic mechanisms of TiO2 NPs with different crystalline forms. These findings suggest prioritizing the use of RT when TiO2 NPs are necessary in agricultural development to minimize toxicity risks.

Effects of Nano Silver and Indole Butyric Acid Application on Growth and Some Physiological Characteristics on Hardwood Cutting of Dalbergia sissoo Roxb

Nanosilver (NS) and indole-3-butyric acid (IBA) can improve cutting performance and subsequent growth. This study was performed in Taqtaq city in a randomized complete block design to study the effects of NS (30, 60, and 90 mg/L) and IBA (50, 100, and 200 mg/L) in addition to distilled water as a control on growth and some characteristics of hardwood cutting of Dalbergia sissoo Roxb. Application of IBA enhanced significantly buds sprouting, where the cutting treated with 50 mg/L IBA sprouted after 35.53 days. IBA at 200 mg/L increased plant leaf area significantly to 204.11 dm2 in comparison to the control cuttings (122.00 dm2). Furthermore, IBA at 50 and 200 mg/L increased the number of leaves to 194.66 and 193.00 leaves/plant, compared to control cuttings (158 leaves/plant). The lowest peroxidase activity (902.00 and 903.30 absorbing units/ g fresh leaves) was observed in the cuttings soaked in 30 and 60 mg/L NS, respectively. Both NS and IBA had a significant effect on macro and microelements in the shoot except Mg and Fe. The shoot content of elements was different in response to NS and IBA applications, whereas the high level of IBA decreased significantly K content (25.80 %) it increased significantly the shoot content of Zn (0.22%). However the lowest concentration of NS (30 mg/L) decreased significantly the Cu content (0.02 %) and increased significantly the shoot content of Mn (0.58%). Root response to NS and IBA also was different, where 90 mg/L NS increased significantly each of K (26.40%) and Zn content (0.68 %), whereas it decreased significantly the root content of Fe (8.78%). The enhancement effects of IBA were more than that of NS on most studied characteristics.

The transcription factor OsNAC5 regulates cadmium accumulation in rice

Cadmium (Cd) is a hazardous heavy metal that threatens human health through the consumption of contaminated rice. To mitigate Cd accumulation in rice grains, it is crucial to reduce Cd uptake. Nevertheless, the transcriptional mechanisms governing Cd uptake in rice remain largely unknown. This research identifies the transcription factor OsNAC5 in Oryza sativa as a positive regulator of the Cd transporter gene OsNRAMP1, thereby influencing Cd uptake. OsNAC5 is predominantly expressed in the roots, resides in the nucleus, and is upregulated by Cd-induced hydrogen peroxide (H2O2). Knocking out OsNAC5 results in lower Cd concentrations in both shoots and roots and heightens sensitivity to Cd. The expression of OsNRAMP1, enhanced by Cd stress, is dependent on OsNAC5. OsNAC5 binds to "CATGTG" motifs in the OsNRAMP1 promoter, activating its expression. The loss of OsNAC5 function leads to reduced Cd accumulation in rice grains. Our findings provide insights into the transcriptional regulation of Cd stress response in rice and propose biotechnological strategies to lower Cd uptake in crops.