A Novel Nutrient- and Antioxidant-Based Formulation Can Sustain Tomato Production under Full Watering and Drought Stress in Saline Soil.

As a result of the climate changes that are getting worse nowadays, drought stress (DS) is a major obstacle during crop life stages, which ultimately reduces tomato crop yields. So, there is a need to adopt modern approaches like a novel nutrient- and antioxidant-based formulation (NABF) for boosting tomato crop productivity. NABF consists of antioxidants (i.e., citric acid, salicylic acid, ascorbic acid, glutathione, and EDTA) and nutrients making it a fruitful growth stimulator against environmental stressors. As a first report, this study was scheduled to investigate the foliar application of NABF on growth and production traits, physio-biochemical attributes, water use efficiency (WUE), and nutritional, hormonal, and antioxidative status of tomato plants cultivated under full watering (100% of ETc) and DS (80 or 60% of ETc). Stressed tomato plants treated with NABF had higher DS tolerance through improved traits of photosynthetic efficiency, leaf integrity, various nutrients (i.e., copper, zinc, manganese, calcium, potassium, phosphorus, and nitrogen), and hormonal contents. These positives were a result of lower levels of oxidative stress biomarkers as a result of enhanced osmoprotectants (soluble sugars, proline, and soluble protein), and non-enzymatic and enzymatic antioxidant activities. Growth, yield, and fruit quality traits, as well as WUE, were improved. Full watering with application of 2.5 g NABF L-1 collected 121 t tomato fruits per hectare as the best treatment. Under moderate DS (80% of ETc), NABF application increased fruit yield by 10.3%, while, under severe DS (40% of ETc), the same fruit yield was obtained compared to full irrigation without NABF. Therefore, the application of 60% ETc × NABF was explored to not only give a similar yield with higher quality compared to 100% ETc without NABF as well as increase WUE.

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.

Nitrogen-molybdenum-manganese co-fertilization reduces nitrate accumulation and enhances spinach (Spinacia oleracea L.) yield and its quality.

Spinach (Spinacia oleracea L.) is considered a nitrogen (N) intensive plant with high nitrate (NO3 -) accumulation in its leaves. The current study via a two-year field trial introduced an approach by combining N fertilization from different sources (e.g., ammonium nitrate; 33.5 % N, and urea; 48 % N) at different rates (180, and 360 kg N ha-1) with the foliar spraying of molybdenum (Mo) as sodium molybdate, and/or manganese (Mn) as manganese sulphate at rates of 50 and 100 mgL-1 of each or with a mixture of Mo and Mn at rates of 50 and 50 mg L-1, respectively on growth, chemical constituents, and NO3 - accumulation in spinach leaves. Our findings revealed that the highest rate of N fertilization (360 kg N ha-1) significantly increased most of the measured parameters e.g., plant length, fresh and dry weight plant-1, number of leaves plant-1, leaf area plant-1, leaf pigments (chlorophyll a, b and carotenoids), nutrients (N, P, K, Fe, Mn, Zn), total soluble carbohydrates, protein content, net assimilation rate, and NO3 - accumulation, but decreased leaf area ratio and relative growth rate. Moreover, plants received urea-N fertilizer gave the highest values of all previous attributes when compared with ammonium nitrate -N fertilizers, and the lowest values of NO3 - accumulation. The co-fertilization of N-Mo-Mn gave the highest values in all studied attributes and the lowest NO3 - accumulation. The best treatment was recorded under the treatment of 360 kg N-urea ha-1 in parallel with the combined foliar application of Mo and Mn (50 + 50 mg L-1). Our findings proposed that the co-fertilization of N-Mo-Mn could enhance spinach yield and its quality, while reducing NO3 - accumulation in leaves, resulting agronomical, environmental and economic benefits.

Natural Biostimulant Attenuates Salinity Stress Effects in Chili Pepper by Remodeling Antioxidant, Ion, and Phytohormone Balances, and Augments Gene Expression.

A biostimulant is any microorganism or substance used to enhance the efficiency of nutrition, tolerance to abiotic stress and/or quality traits of crops, depending on its contents from nutrients. Plant biostimulants like honey bee (HB) and silymarin (Sm) are a strategic trend for managing stressed crops by promoting nutritional and hormonal balance, regulating osmotic protectors, antioxidants, and genetic potential, reflecting plant growth and productivity. We applied diluted honey bee (HB) and silymarin-enriched honey bee (HB- Sm) as foliar nourishment to investigate their improving influences on growth, yield, nutritional and hormonal balance, various osmoprotectant levels, different components of antioxidant system, and genetic potential of chili pepper plants grown under NaCl-salinity stress (10 dS m‒1). HB significantly promoted the examined attributes and HB-Sm conferred optimal values, including growth, productivity, K+/Na+ ratio, capsaicin, and Sm contents. The antioxidative defense components were significantly better than those obtained with HB alone. Conversely, levels of oxidative stress markers (superoxide ions and hydrogen peroxide) and parameters related to membrane damage (malondialdehyde level, stability index, ionic leakage, Na+, and Cl- contents) were significantly reduced. HB-Sm significantly affects inactive gene expression, as a natural biostimulator silencing active gene expression. SCoT primers were used as proof in salt-treated or untreated chili pepper plants. There were 41 cDNA amplicons selected by SCoT-primers. Twenty of them were EcDNA amplicons (cDNA-amplicons that enhanced their genes by one or more treatments) representing 49% of all cDNA amplicons, whereas 7 amplicons for ScDNA (whose genes were silenced in one or more treatments) represented 17%, and 14 McDNA (monomorphic cDNA-amplicons with control) amplicons were represented by 34% from all cDNA amplicons. This indicates the high effect of BH-Sm treatments in expression enhancement of some inactive genes and their silenced effect for expression of some active genes, also confirming that cDNA-SCoT markers succeeded in detection of variable gene expression patterns between the untreated and treated plants. In conclusion, HB-Sm as a natural multi-biostimulator can attenuate salt stress effects in chili pepper plants by remodeling the antioxidant defense system and ameliorating plant productivity.

Revitalizing Fertility of Nutrient-Deficient Virgin Sandy Soil Using Leguminous Biocompost Boosts Phaseolus vulgaris Performance.

During the 2019 and 2020 seasons, nutrient-deficient virgin sandy soil was examined along with the investigation of the response of Phaseolus vulgaris plants to soil application with biocompost in integration with chemical fertilizers applied to soil and plants. Four treatments (100% of the recommended NPK fertilizer dose (control), 75% NPK applied to soil + 25% foliar spray, 75% NPK applied to soil + 25% foliar spray + leguminous compost (CL), and 75% NPK applied to soil + 25% foliar spray + CL containing Bacillus subtilis (biocompost; CLB)) were applied in a randomized complete block design. The 75% NPK applied to soil + 25% foliar spray + CLB was the best treatment, which exceeded other treatments in improving soil fertility and plant performance. It noticeably improved soil physicochemical properties, including available nutrients, activities of various soil enzymes (cellulase, invertase, urease, and catalase), soil cation exchange capacity, organic carbon content, and pH, as well as plant growth and productivity, and plant physiobiochemistry, including nutrients and water contents, and various antioxidant activities. The results of the 2020 season significantly outperformed those of the 2019 season, indicating the positive effects of biofertilizers as a strategy to combine soil supplementation with NPK fertilizers and allocate a portion of NPK fertilizers for foliar spraying of plants in nutrient-deficient sandy soils.