Summary Two field experiments on common bean (Phaseolus vulgaris L.) plants were conducted at three sites having different levels of salinity (EC = 1.84, 6.03, or 8.97 dS m^–1) and considered to be low, moderate, or highly saline soil, respectively. The aim was to examine the effects of three successive exogenous applications of 5.0 mM proline, applied as foliar sprays at 20, 30, and 40 d after sowing (DAS) to each plant at each site. Bean plants were sampled 50 DAS and the effects of the proline sprays on various growth parameters, levels of photosynthetic pigments, endogenous proline, ascorbic acid, nitrate, nitrite, and mineral nutrient (P, K, Na) concentrations, and anti-oxidant enzyme activities were measured in order to understand the mechanism(s) of salt tolerance in proline-treated bean plants. Exogenous applications of 5 mM proline alleviated oxidative stress and enhanced the growth of all treated common bean plants. Proline also increased the activities of the anti-oxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as the concentrations of carotenoids, ascorbic acid, and endogenous proline. Spray applications of proline increased the concentrations of P and K⁺, and decreased Na⁺ ion concentrations, in salt-affected plants. Thus, the K⁺:Na⁺ ratio increased. Based on these findings, we recommend the use of proline as a commercial formulation to enhance plant growth and production in common bean plants grown under saline conditions.

In two experiments, conducted in 2011 and in 2012, 14 different growing media were prepared from peat moss, vermiculite, and/or perlite with or without 0.5 g l^–1 humic acid (HA) to determine the optimum growing medium for eggplant (Solanum melongena L.) and tomato (Lycopersicum esculentum Mill.) transplants. None of the media tested affected the percentages of seedling emergence or survival in either crop, although the rates of emergence were affected. Higher dry weights, relative water contents, membrane stability indices, and N, P, and K uptake values were recorded for eggplant and tomato transplants in all HA-supplemented media than in the corresponding HA-free media. In terms of efficacy, the best medium among all 14 tested was 0.5 g l^–1 HA + 50% (v/v) vermiculite + 50% (v/v) perlite, followed by 0.5 g HA + 65% (v/v) vermiculite + 35% (v/v) perlite, then 50% (v/v) vermiculite + 50% (v/v) perlite without HA. The first medium was significantly better for all traits measured than the standard medium currently used for tomato and eggplant transplant production in Middle Eastern countries.

The effects of sulphur (S) and/or humic acid (HA) on the growth, leaf anti-oxidant levels, leaf nutrients, and yields of pea (Pisum sativum L.) plants grown on reclaimed saline soil (EC = 8.2 – 8.5 dS m^–1) were investigated. Two field experiments were performed in a completely randomised design with four treatments and four replicates for each treatment. Sulphur and HA were applied at the rates of 500 kg ha^–1 or 200 kg ha^–1, respectively, singly or in combination. Neither S nor HA was included in the controls. Soil application of S and/or HA significantly increased shoot lengths, the number of branches plant^–1, leaf area plant^–1, shoot dry weight plant^–1, the contents of leaf pigments, leaf free proline, leaf macronutrients (N, P, and K), seed protein, and the total yields of pods and seeds ha^–1, when compared with non-treated control plants. In contrast, there were significant reductions in leaf Na⁺ ion contents under the S and/or HA treatments. The combined S + HA treatment was found to be highly effective at improving the growth and yield of pea plants by alleviating the inhibitory effects of soil salinity stress.The same trends were observed over two growing seasons (2010 and 2011).

To study the effect of soil application of potassium humate (KH) (0, 70 and 140 Kg ha⁻¹) on agronomic, biochemical attributes, and yield and its components on bean (Phaseolus vulgaris L.) cultivars ‘Bronco’ grown under two sites having different level of salinity (EC = 3.00 or 5.00 ± 0.20 dS m⁻¹). Two field trials were conducted at the Agriculture Test Station, Faculty of Agriculture, Fayoum University, in 2014 and 2015. The obtained results indicated that addition of KH increased all of the studied growth parameters, i.e. plant height, number of leaves, leaf area, stem diameter and canopy dry weight. Moreover addition of KH significantly increased membrane permeability measurements. KH significantly increased chemical composition related to salt tolerant either inorganic e.g. N, P, K, and decreased Na and Cl contents of leaves or organic components e.g. chlorophyll a + b, carotenoids, anthocyanin total phenolics, total flavonoids and proline. DPPH radical-scavenging activity and yield and its components were increased. The soil application of KH was found to be highly effective at improving the growth and yield of bean plants by alleviating the inhibitory effects of soil salinity stress.

The use of bio-stimulants (BSs) has become an important policy in managing many stressed crop plants through the regulation of the balance of phytohormones, osmo-protectors (OPs), antioxidant systems, and gene expression, all of which reflect plant growth and productivity. Garlic + onion extract (GOE) at a concentration of 2.0–3.0% and diluted bee honey solution (BHs) at a concentration of 1.0–1.5% were applied exogenously to squash (Cucurbita pepo) plants subjected to cadmium (Cd) + lead (Pb) stress (0.3 mM CdCl₂ + 0.3 mM PbCl₂). The objective was to determine the effects of these treatments on growth characteristics, organic metabolites/biomolecules, and mineral nutrients. Cd + Pb stress significantly increased electrolyte leakage (EL, 103%) and malondialdehyde (MDA, 90%) because of an increase in hydrogen peroxide (H₂O₂, 145%) and superoxide (O₂^•−, 152%) levels, and contents of abscisic acid (ABA, 164%), Cd (674–711%), and Pb (754–805%). Consequently, marked increases in the contents of OPs and non-enzymatic antioxidants (28–133%), activities of antioxidant enzymes (48–80%), and expressions of enzyme genes (60–84%) were observed. The administration of Cd + Pb treatment reduced plant growth and development parameters (25–59%), yield components (61–86%), photosynthetic components (27–67%), leaf proportional water content (26%), indole-3-acetic acid (IAA, 44%), gibberellic acid (GA₃, 56%), and cyto-kinin (CKs, 49%) contents. Nonetheless, the administration of GOE, BHs, and GOE + BHs attenuated the adverse impacts of Cd + Pb stress. The best treatment was GOE + BHs which significantly decreased EL (52%) and MDA (49%) because of a reduction of O₂^•– (61%), H₂O₂ (60%), ABA (63%), Cd (89–91%), and Pb (89–91%) levels. This positive outcome was linked to an increase in the OPs’ (22–46%) and non-enzymatic antioxidant (27–46%) levels, activities of enzymes (26–44%), and enzyme gene expressions (35–40%), all of which contributed to the promoted relative water content (RWC, 37%), pigment contents (47–194%), hormonal levels (82–132%), growth traits (31–149%), yield components (154–626%), and fruit quality traits (31–92%). From these results, it can be concluded that treatment of GOE + BHs is recommended as a foliar application to reduce the adverse effects of Cd + Pb stress treatment in squash.