S. Farouk

Salinity is a key worldwide ecological restriction to sustainable crop production and food security. Various methods were used for inducing salinity tolerance including biotechnological approaches or application of stress tolerance-inducing substances. Silicon supplementation has a decisive role in alleviating of salinity injury, however, the definite mechanisms behind stay scantily understood, and must be examined. The imperative roles of sodium metasilicate (Si, 100 ppm) application methods (foliar spraying at 100 mg/l; soil additive at 100 mg/kg soil; foliar spraying at 100 mg/l plus soil additive at 100 mg/kg soil), in improving growth and essential oil yield, maintaining water status, activating antioxidant system, and keeping ion homeostasis of salt affected-sweet basil (6000 mg NaCl/kg soil) were studied. Salinity induced a notable increase in oxidative biomarkers, coupled with higher osmolyte concentration and osmotic potential (OP) values, as well as increased superoxide dismutase and peroxidase activities. Alternatively, sweet basil growth, essential oil yield, and catalase activity were reduced under salinity. Furthermore, salinity aggravated ion imbalance, decreased photosynthetic pigment and disrupted the plants' water status. Silicon application drastically increased osmolyte accumulation associated with sustained water status, increased OP, and improved osmotic adjustment (OA) capacity. Additionally, Si application enhanced antioxidant aptitude associated with decreased oxidative biomarkers and improved growth, photosynthetic pigment, and essential oil yield. Greater outcomes were achieved with the foliar spraying method, compared with other application methods. Salinity stress evoked modification in protein assimilation capacity and possibly will withdraw protein biosynthesis and reduce total protein band number; however, Si application may adjust the expression of salinity inducible proteins. Foliar spraying of Si with or without soil additive accelerates the expression of peroxidase isozyme over salinized or control plants. Collectively, Si foliar spraying alleviated salinity-related injuries on sweet basil by maintaining water status, increasing osmolyte assimilation, improving OA, enhancing redox homeostasis, and antioxidant capacity.

Water stress impaired cowpea plant growth and decreased ion percentage and chlorophyll and carbohydrate concentration in the shoot as well as yield and its quality. Foliar-applied chitosan, in particular 250 mg/l, increased plant growth, yield and its quality as well as physiological constituents in plant shoot under stressed or nonstressed conditions as compared to untreated plants. Anatomically, water stress decreased thickness of leaf blade at midrib region, thickness of mesophyll tissue, thickness of midrib vascular bundle. Treatment with chitosan, in particular, 250 mg/l and their interactions with stress conditions increased all the above mentioned parameters in either non-stressed or stressed plants. It is suggested that the severity of cowpea plants damaged from water stress was reduced by 250 mg/l chitosan application.Keywords: water stress, chitosan, cowpea, anatomy, growth, yield.

Salinity is persistently a decisive feature confining agricultural sustainability and food security in arid and semi-arid regions. Biochar (Bi) has been advocated as a means of lessening climate changes by sequestering carbon, concurrently supplying energy and rising crop productivity under normal or stressful conditions. Melatonin (Mt) has been shown to mediate numerous biochemical pathways and play important roles in mitigating multi-stress factors. However, their integrated roles in mitigating salt toxicity remain largely inexpressible. A completely randomized design was conducted to realize the remediation potential of Bi and/or Mt in attenuation salinity injury on borage plants by evaluating its effects on growth, water status, osmotic adjustment, antioxidant capacity, ions, and finally the yield. Salinity stress significantly decreased the plant growth and attributed yield when compared with non-salinized control plants. The depression effect of salinity on borage productivity was associated with the reduction in photosynthetic pigment and ascorbic acid (AsA) concentrations, potassium (K+) percentage, K+-translocation, and potassium/sodium ratio as well as catalase (CAT) activity. Additionally, borage plants’ water status was disrupted by salinity through decreasing water content (WC), relative water content (RWC), and water retention capacity (WTC), as well as water potential (Ψw), osmotic potential (Ψs), and turgor potential (Ψp). Moreover, salinity stress evoked oxidative bursts via hyper-accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA), as well as protein carbonyl, which is associated with membrane dysfunction. The oxidative burst was connected with the hyper-accumulation of sodium (Na+) and chloride (Cl−) in plant tissues, coupled with osmolytes’ accumulation and accelerating plants’ osmotic adjustment (OA) capacity. The addition of Bi and/or Mt had a positive effect in mitigating salinity on borage plants by reducing Cl−, Na+, and Na+-translocation, and oxidative biomarkers as well as Ψw, Ψs, and Ψp. Moreover, Bi and/or Mt addition to salt-affected plants increased plant growth and yield by improving plant water status and OA capacity associated with the activation of antioxidant capacity and osmolytes accumulation as well as increased photosynthetic pigments, K+, and K+/Na+ ratio. Considering these observations, Bi and/or Mt can be used as a promising approach for enhancing the productivity of salt-affected borage plants due to their roles in sustaining water relations, rising solutes synthesis, progressing OA, improving redox homeostasis, and antioxidant aptitude.

Soil salinity is the main obstacle to worldwide sustainable productivity and food security. Zinc sulfate (Zn) and paclobutrazol (PBZ) as a cost-effective agent, has multiple biochemical functions in plant productivity. Meanwhile, their synergistic effects on inducing salt tolerance are indecisive and not often reported. A pot experiment was done for evaluating the defensive function of Zn (100 mg/L) or PBZ (200 mg/L) on salt (0, 50, 100 mM NaCl) affected pea plant growth, photosynthetic pigment, ions, antioxidant capacity, and yield. Salinity stress significantly reduces all growth and yield attributes of pea plants relative to nonsalinized treatment. This reduction was accompanied by a decline in chlorophyll, nitrogen, phosphorus, and potassium (K+), the ratio between K+ and sodium (Na+), as well as reduced glutathione (GSH) and glutathione reductase (GR). Alternatively, salinity increased Na+, carotenoid (CAR), proline (PRO), ascorbic acid (AsA), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) over nonsalinized treatment. Foliar spraying with Zn and PBZ under normal condition increased plant growth, nitrogen, phosphorus, potassium, K+/Na+ ratio, CAR, PRO, AsA, GSH, APX, GR, and yield and its quality, meanwhile decreased Na+ over nonsprayed plants. Application of Zn and PBZ counteracted the harmful effects of salinity on pea plants, by upregulating the antioxidant system, ion homeostasis, and improving chlorophyll biosynthesis that induced plant growth and yield components. In conclusion, Zn plus PBZ application at 30 and 45 days from sowing offset the injuries of salinity on pea plant growth and yield by upregulating the antioxidant capacity and increasing photosynthetic pigments.