Incorporation of compost and biochar enhances yield and medicinal compounds in seeds of water-stressed Trigonella foenum-graecum L. plants cultivated in saline calcareous soils.

BACKGROUND: The combination of compost and biochar (CB) plays an important role in soil restoration and mitigation strategies against drought stress in plants. In the current study, the impact of CB was determined on the characteristics of saline calcareous soil and the productivity of fenugreek (Trigonella foenum-graecum L.) plants. The field trials examined CB rates (CB0, CB10 and CB20 corresponding to 0, 10, and 20 t ha‒1, respectively) under deficit irrigation [DI0%, DI20%, and DI40% receiving 100, 80, and 60% crop evapotranspiration (ETc), respectively] conditions on growth, seed yield (SY), quality, and water productivity (WP) of fenugreek grown in saline calcareous soils. RESULTS: In general, DI negatively affected the morpho-physio-biochemical responses in plants cultivated in saline calcareous soils. However, amendments of CB10 or CB20 improved soil structure under DI conditions. This was evidenced by the decreased pH, electrical conductivity of soil extract (ECe), and bulk density but increased organic matter, macronutrient (N, P, and K) availability, water retention, and total porosity; thus, maintaining better water and nutritional status. These soil modifications improved chlorophyll, tissue water contents, cell membrane stability, photosystem II photochemical efficiency, photosynthetic performance, and nutritional homeostasis of drought-stressed plants. This was also supported by increased osmolytes, non-enzymatic, and enzymatic activities under DI conditions. Regardless of DI regimes, SY was significantly (P ≤ 0.05) improved by 40.0 and 102.5% when plants were treated with CB10 and CB20, respectively, as similarly observed for seed alkaloids (87.0, and 39.1%), trigonelline content (43.8, and 16.7%) and WP (40.9, and 104.5%) over unamended control plants. CONCLUSIONS: Overall, the application of organic amendments of CB can be a promising sustainable solution for improving saline calcareous soil properties, mitigating the negative effects of DI stress, and enhancing crop productivity in arid and semi-arid agro-climates.

Effect of Eco-Friendly Application of Bee Honey Solution on Yield, Physio-Chemical, Antioxidants, and Enzyme Gene Expressions in Excessive Nitrogen-Stressed Common Bean (Phaseolus vulgaris L.) Plants.

Excessive use of nitrogen (N) pollutes the environment and causes greenhouse gas emissions; however, the application of eco-friendly plant biostimulators (BSs) can overcome these issues. Therefore, this paper aimed to explore the role of diluted bee honey solution (DHS) in attenuating the adverse impacts of N toxicity on Phaseolus vulgaris growth, yield quality, physio-chemical properties, and defense systems. For this purpose, the soil was fertilized with 100, 125, and 150% of the recommended N dose (RND), and the plants were sprayed with 1.5% DHS. Trials were arranged in a two-factor split-plot design (N levels occupied main plots × DH- occupied subplots). Excess N (150% RND) caused a significant decline in plant growth, yield quality, photosynthesis, and antioxidants, while significantly increasing oxidants and oxidative damage [hydrogen peroxide (H2O2), superoxide (O2•-), nitrate, electrolyte leakage (EL), and malondialdehyde (MDA) levels]. However, DHS significantly improved antioxidant activities (glutathione and nitrate reductases, catalase, ascorbate peroxidase, superoxide dismutase, proline, ascorbate, α-tocopherol, and glutathione) and osmoregulatory levels (soluble protein, glycine betaine, and soluble sugars). Enzyme gene expressions showed the same trend as enzyme activities. Additionally, H2O2, O2•-, EL, MDA, and nitrate levels were significantly declined, reflecting enhanced growth, yield, fruit quality, and photosynthetic efficiency. The results demonstrate that DHS can be used as an eco-friendly approach to overcome the harmful impacts of N toxicity on P. vulgaris plants.

Antioxidant and Anticancer Assessment and Phytochemical Investigation of Three Varieties of Date Fruits.

Date palm (Phoenix dactylifera L.) fruits contain high concentrations of phenolic compounds, particularly flavonoids and other micronutrients, which impact human health due to their potent antioxidant, anti-inflammatory, and anticancer characteristics. In the present study, the effect of ethyl acetate, hydroethanol, hydromethanol, and aqueous extract from three date palm varieties (i.e., Ajwa, Siwi, and Sukkari) on phytochemical profiles and antioxidant and anticancer activities was investigated. Fruit extracts were screened for their antioxidant activity using the DPPH· method. Phenolic constituents were quantified and identified using HPLC-DAD. Extracts (ethyl acetate, hydroethanol, and hydromethanol) were assessed for cytotoxicity on nine human cancer cell lines, i.e., MG-63, HCT116, MCF7, MDA-MB-231, HEPG2, HUH7, A549, H460, and HFB4, using the sulphorhodamine-B (SRB) assay. Results showed that the ethyl acetate extract of the Sukkari fruits has the greatest antioxidant potential with an IC50 value of 132.4 ± 0.3 µg·mL-1, while the aqueous extract of Ajwa date fruits exhibited the lowest antioxidant effect with an IC50 value of 867.1 ± 0.3 µg·mL-1. The extracts exhibited potent to moderate anticancer activities against the investigated cancer cell line in a source-dependent manner. Methanol extract of Siwi fruits exhibited the most potent anticancer activity (IC50 = 99 ± 1.6 µg·mL-1), followed by the same extract of Sukkari fruits with an IC50 value of 119 ± 3.5 µg·mL-1 against the cell line of human breast cancer (MDA-MB-231). Additionally, principal component analysis (PCA) was investigated to determine the relationship among the investigated traits and treatments. Our findings reveal that date palm fruit-derived extracts are excellent sources of biologically active constituents and substantiate their potential use in new anticancer strategies from natural resources.

Glutathione-mediated changes in productivity, photosynthetic efficiency, osmolytes, and antioxidant capacity of common beans (Phaseolus vulgaris) grown under water deficit.

Globally, salinity and drought are severe abiotic stresses that presently threaten vegetable production. This study investigates the potential exogenously-applied glutathione (GSH) to relieve water deficits on Phaseolus vulgaris plants cultivated in saline soil conditions (6.22 dS m-1) by evaluating agronomic, stability index of membrane, water satatus, osmolytes, and antioxidant capacity responses. During two open field growing seasons (2017 and 2018), foliar spraying of glutathione (GSH) at 0.5 (GSH1) or 1.0 (GSH1) mM and three irrigation rates (I100 = 100%, I80 = 80% and I60 = 60% of the crop evapotranspiration) were applied to common bean plants. Water deficits significantly decreased common bean growth, green pods yield, integrity of the membranes, plant water status, SPAD chlorophyll index, and photosynthetic capacity (Fv/Fm, PI), while not improving the irrigation use efficiency (IUE) compared to full irrigation. Foliar-applied GSH markedly lessened drought-induced damages to bean plants, by enhancing the above variables. The integrative I80 + GSH1 or GSH2 and I60 + GSH1 or GSH2 elevated the IUE and exceeded the full irrigation without GSH application (I100) treatment by 38% and 37%, and 33% and 28%, respectively. Drought stress increased proline and total soluble sugars content while decreased the total free amino acids content. However, GSH-supplemented drought-stressed plants mediated further increases in all analyzed osmolytes contents. Exogenous GSH enhanced the common bean antioxidative machinery, being promoted the glutathione and ascorbic acid content as well as up-regulated the activity of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione peroxidase. These findings demonstrate the efficacy of exogenous GSH in alleviating water deficit in bean plants cultivated in salty soil.

Simultaneous Action of Silymarin and Dopamine Enhances Defense Mechanisms Related to Antioxidants, Polyamine Metabolic Enzymes, and Tolerance to Cadmium Stress in Phaseolus vulgaris.

Silymarin (Sm) and dopamine (DA) act synergistically as potential antioxidants, mediating many physiological and biochemical processes. As a first report, we investigated the synergistic effect of Sm and DA in mitigating cadmium stress in Phaseolus vulgaris plants. Three experiments were conducted simultaneously using 40 cm diameter pots to elucidate how Sm and DA affect cadmium tolerance traits at morphological, physiological, and biochemical levels. Cadmium stress triggered a marked reduction in growth, productivity, and physio-biochemical characteristics of common bean plants compared to unstressed plants. Seed priming (SP) and foliar spraying (FS) with silymarin (Sm) or dopamine (DA) ((DA (SP) + Sm (FS) and Sm (SP) + DA (FS)) ameliorated the damaging effects of cadmium stress. Sm seed priming + DA foliar spraying (Sm (SP) + DA (FS)) was more efficient. The treated stressed common bean plants showed greater tolerance to cadmium stress by diminishing oxidative stress biomarkers (i.e., O2•-, H2O2, and MDA) levels through enhanced enzymatic (SOD, CAT, POD, APX) and non-enzymatic (ascorbic acid, glutathione, α-tocopherol, choline, phenolics, flavonoids) antioxidant activities and osmoprotectants (proline, glycine betaine, and soluble sugars) contents, as well as through improved photosynthetic efficiency (total chlorophyll and carotenoids contents, photochemical activity, and efficiencies of carboxylation (iCE) and PSII (Fv/Fm)), polyamines (Put, Spd, and Spm), and polyamine metabolic enzymes (ADC and ODC) accumulation. These findings signify that Sm and DA have remarkable anti-stress effects, which can help regulate plant self-defense systems, reflecting satisfactory plant growth and productivity. Thus, realizing the synergistic effect of Sm and DA in cadmium tolerance confers potential new capabilities for these compounds to function in sustainable agriculture.

Soil application of effective microorganisms and nitrogen alleviates salt stress in hot pepper (Capsicum annum L.) plants.

The application of effective microorganisms (EMs) and/or nitrogen (N) have a stimulating effect on plants against abiotic stress conditions. The aim of the present study was to determine the impact of the co-application of EMs and N on growth, physio-biochemical attributes, anatomical structures, nutrients acquisition, capsaicin, protein, and osmoprotectant contents, as well as the antioxidative defense system of hot pepper (Capsicum annum L.) plants. In the field trials, EMs were not applied (EMs-) or applied (EMs+) along with three N rates of 120, 150, and 180 kg unit N ha-1 (designated as N120, N150, and N180, respectively) to hot pepper plants grown in saline soils (9.6 dS m-1). The application of EMs and/or high N levels attenuated the salt-induced damages to hot pepper growth and yield. The application of EMs+ with either N150 or N180 increased the number, average weight and yield of fruits by 14.4 or 17.0%, 20.8 or 20.8% and 28.4 or 27.5%, respectively, compared to hot pepper plants treated with the recommended dose (EMs- × N150). When EMs+ was individually applied or combined with either N150 or N180, increased accumulation of capsaicin were observed by 16.7 or 20.8%, protein by 12.5 or 16.7%, proline by 19.0 or 14.3%, and total soluble sugars by 3.7 or 7.4%, respectively, in comparison with those treated with the integrative EMs- × N150. In addition, the non-enzymatic contents (ascorbate, and glutathione) and enzymatic activities (catalase, superoxide dismutase, and glutathione reductase) of the antioxidant defense systems significantly increased in hot pepper plants treated with EMs+ alone or combined with N150 or N180 under salt stress conditions. Higher accumulation of nutrients (N, P, K+, and Ca2+) along with reduced Na+ acquisition was also evidenced in response to EMs+ or/and high N levels. Most anatomical features of stems and leaves recovered in hot pepper plants grown in saline soils and supplied with EMs+ and N. The application of EMs and N is undoubtedly opening new sustainable approaches toward enhancing abiotic stress tolerance in crops (e.g. hot pepper).

Sequential Antioxidants Foliar Application Can Alleviate Negative Consequences of Salinity Stress in Vicia faba L.

Salinity is one of the most limiting abiotic stresses in agricultural productivity. Exogenously applied antioxidants successfully enabled salt-stressed plants to cope with stress. Two-season field experiments were conducted consecutively in 2016/17 and 2017/18 to study the effects of foliar applications of singular (ascorbate, AsA; proline, Pro; and glutathione, GSH) or sequential (AsA-Pro-GSH and GSH-Pro-AsA) antioxidants on growth, yield, physio-biochemical attributes, and enzymatic and non-enzymatic antioxidative defense system of Vicia faba L. (CV. Sakha-1) plants grown under saline soil conditions (EC = 4.53 dS m-1). Under soil salinity conditions, AsA, Pro, or GSH-Pro-ASA improved growth and productivity, photosynthesis efficiency, stomatal conductance (gs), plant water status, as well as enzymatic and non-enzymatic antioxidants. However, sequential AsA-Pro-GSH foliar application followed by singular GSH significantly exceeded all other treatments (i.e., AsA, Pro, and GSH-Pro-AsA), improving growth characteristics (shoot length, shoot fresh and dry weights, and leaves area), photosynthesis efficiency, stomatal conductance, plant water status, and yield and its components (green pods weight/plant-1, green pods yield/hectare-1, and seed yield/hectare-1), as well as enzymatic (ascorbate peroxidase, catalase, superoxide dismutase, and glutathione reductase) and non-enzymatic (AsA, GSH, Pro, phenolic aglycone, phenolic glycosides) antioxidants compared to control. Overall, our results clearly demonstrate that sequential AsA-Pro-GSH foliar application has a positive effect on salt-stressed Vicia faba plants.

Foliar Application of Zinc Oxide Nanoparticles Promotes Drought Stress Tolerance in Eggplant (Solanum melongena L.).

Water shortage and salinity are major challenges for sustaining global food security. Using nutrients in the nano-scale formulation including zinc oxide nanoparticles (ZnO NP) is a novel fertilization strategy for crops. In this study, two field-based trials were conducted during 2018 and 2019 to examine the influence of three ZnO NP concentrations (0, 50, and 100 ppm) in eggplant grown under full irrigation (100 of crop evapotranspiration; ETc) and drought stress (60% of ETc). Plant growth, yield, water productivity (WP), physiology, biochemistry, and anatomy responses were evaluated. Drought stress significantly decreased membrane stability index (MSI), relative water content (RWC), and photosynthetic efficiency, thus hampered eggplant growth and yield. In contrast, exogenous ZnO NP to water-stressed eggplant resulted in increased RWC and MSI associated with improved stem and leaf anatomical structures and enhanced photosynthetic efficiency. Under drought stress, supplementation of 50 and 100 ppm ZnO NP improved growth characteristics and increased fruit yield by 12.2% and 22.6%, respectively, compared with fully irrigated plants and nonapplied ZnO NP. The highest water productivity (WP) was obtained when eggplant was irrigated with 60% ETc and foliarly treated with 50 or 100 ppm of ZnO NP, which led to 50.8-66.1% increases in WP when compared with nontreated fully irrigated plants. Collectively, these findings demonstrated that foliar spraying ZnO NP gives the utility for alleviating drought stress effects on eggplant cultivated in saline soil.

Sequential Application of Antioxidants Rectifies Ion Imbalance and Strengthens Antioxidant Systems in Salt-Stressed Cucumber.

Exogenous antioxidant applications enable salt-stressed plants to successfully cope with different environmental stresses. The objectives of this investigation were to study the effects of sequential treatments of proline (Pro), ascorbic acid (AsA), and/or glutathione (GSH) on 100 mM NaCl-stressed cucumber transplant's physio-biochemical and growth traits as well as systems of antioxidant defense. Under salinity stress, different treatment of AsA, Pro, or/and GSH improved growth characteristics, stomatal conductance (gs), enhanced the activities of glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) as well as increased contents of AsA, Pro, and GSH. However, sequential application of antioxidants (GSH-Pro- AsA) significantly exceeded all individual applications, reducing leaf and root Cd2+ and Na+ contents in comparison to the control. In plants grown under NaCl-salt stress, growth characteristics, photosynthetic efficiency, membrane stability index (MSI), relative water content (RWC), contents of root and leaf K+ and Ca2+, and ratios of K+/Na+ and Ca2+/Na+ were notably reduced, while leaf contents of non-enzymatic and enzymatic antioxidants, as well as root and leaf Cd2+ and Na+ concentrations were remarkably increased. However, AsA, Pro, or/and GSH treatments significantly improved all investigated growth characteristics, photosynthetic efficiency, RWC and MSI, as well as AsA, Pro, and GSH, and enzymatic activity, leaf and root K+ and Ca2+ contents and their ratios to Na+, while significantly reduced leaf and root Cd2+ and Na+ contents.

Heavy metals-resistant bacteria (HM-RB): Potential bioremediators of heavy metals-stressed Spinacia oleracea plant.

Microorganism technologies can provide a potential alternative to traditional methods of removing heavy metals to conserve agricultural soils. This study aimed to identify and characterize heavy metals-resistant bacteria (HM-RB) isolated from industry-affected soil and their desired impact as bioremediators of heavy metals-stressed spinach plants. Three of 135 isolates were selected based on a high level of resistance to heavy metals. Based on morphological and biochemical characteristics, the selected isolates were identified as Bacillus subtilis subsp. spizizenii DSM 15029 T DSM (MA3), Paenibacillus jamilae DSM 13815 T DSM (LA22), or Pseudomonas aeruginosa DSM 1117 DSM (SN36). Experiments were implemented to investigate the three isolated HM-RB ability on improving attributes of growth, physio-biochemistry, and components of the antioxidant defense system of spinach plant exposed to the stress of cadmium (Cd2+; 2 mM), lead (Pb2+; 2 mM) or 2 mM Cd2++2 mM Pb2+. Compared to control, Cd2+ or Pb2+ stress markedly lowered plant fresh and dry weights, leaf contents of chlorophylls and carotenoids, rates of transpiration (Tr), net photosynthesis (Pn) and stomatal conductance (gs), relative water content (RWC), and membrane stability index (MSI). In contrast, contents of α.tochopherol (α.TOC), ascorbic acid (AsA), glutathione (GSH), proline, soluble sugars, Cd2+, and Pb2+, as well as activities of enzymatic and non-enzymatic antioxidants were markedly elevated. The application of HM-RB promoted the tolerance to heavy metal stress in spinach plants by improving Tr, Pn, gs, RWC, and MSI, while activities of enzymatic and non-enzymatic antioxidants were suppressed. These results reflected positively in promoting plant growth under heavy metal stress. Therefore, the application of HM-RB as potential bioremediators may be a promising strategy for promoting plant growth and productivity under heavy metal stress.

Land suitability modeling for newly reclaimed area using GIS-based multi-criteria decision analysis.

Selecting the appropriate land use is one of the most important steps toward achieving sustainable development. The main objective of this research is to develop a new method to overcome the contradiction occurring when using the conventional methods to evaluate land suitability for newly reclaimed areas. A spatial model was developed to assess land suitability for wheat in El-Minia Governorate, Egypt, using integration of modeling and geographic information systems-based multi-criteria decision analysis (GIS-MCDA). Land suitability for wheat was performed using two approaches, namely the proposed model (GIS-MCDA) and the parametric method (square root). According to the square root, 75.0% of the study area was classified as not suitable, while the proposed model revealed that 20.5% of the study area was classified as highly suitable and 61.5% as moderately suitable. In order to examine the validity of the proposed model, a comparison was made between the obtained results of both the proposed model and the square root method with the actual yield of the wheat. The correlation coefficient (r) between actual yield and the estimated yield of the square root method was 0.46, while the proposed model gives higher value (r = 0.95), which proves the validity of the proposed model in estimating land suitability for wheat cultivation. The findings of this research revealed that the integration of modeling and GIS-MCDA adopted by the proposed model provides an effective and flexible technique contributing to improve land suitability assessment for wheat in newly reclaimed areas to be more accurate and reliable.

Sequenced ascorbate-proline-glutathione seed treatment elevates cadmium tolerance in cucumber transplants.

During its life cycle, plant has to cope with a number of abiotic stresses including cadmium stress. Cadmium (Cd) is highly toxic to plant and greatly influences its growth and entire metabolism. Antioxidants have to enable plant to beat such stresses. Therefore, effects of ascorbate (AsA), proline (Pro) and glutathione (GSH) applied, as seed soaking solutions, singly or in a sequence on cucumber transplant growth, physio-biochemical attributes and antioxidant defense system activity were investigated under 2 mM Cd stress. Adding Cd to transplants in irrigation water reduced photosynthetic efficiency, and nutrient (K+ and Ca2+) contents, while increased the activity of defense systems (non-enzymatic and enzymatic antioxidants) and Cd2+ contents in roots and leaves. Exogenous AsA, Pro and GSH applied singly or in a sequence improved transplant growth (e.g., shoot length, leaf area, shoot fresh weight and shoot dry weight), photosynthetic efficiency (i.e., SPAD chlorophyll, Fv/Fm and PI), transplant health (i.e., increased leaf MSI and RWC, and decreased root and leaf Cd2+ contents), antioxidant defense systems activity (enzymatic; superoxide dismutase, catalase, glutathione reductase and ascorbate peroxidase, and non-enzymatic; Pro, AsA and GSH antioxidants) and nutrient (K+ and Ca2+) contents. These positive results were obtained under irrigation with or without Cd, AsA. Sequenced AsA-Pro-GSH was the best treatment of which this study recommends to use, followed by GSH treatment, for growing cucumber transplants under Cd stress.