Salt‐ and drought‐induced alterations in citrulline were assessed in 4 local melon genotypes, 2 sensitive (CU‐52, CU‐94) and 2 tolerant (CU‐196, CU‐280), grown in vermiculite in a growth chamber. Salt and drought stresses were started using 30‐day‐old plants, with 250 mM NaCI and 45 mM PEG (−1.0 MPa) and continued for 12 days. After 12 days under salt and drought conditions, the citrulline contents were increased in the tolerant CU 196 to 25.10 μmol gDW⁻¹ and 24.10 μmol gDW⁻¹ for salt and drought stresses, respectively. However, the citrulline contents of the sensitive CU‐52 were 11.68 μmol gDW⁻¹ and 11.76 μmol gDW⁻¹ for salt and drought, respectively. The striking alteration was obtained in the citrulline accumulation. The tolerant melons accumulated 2 times more citrulline than the sensitive melons. For assessing or screening melon genotypes in a large number of accessions or breeding lines for their tolerance to salinity and drought during their young plant stage, the amount of citrulline accumulation in response to the given treatments might be considered as a novel biochemical indicator of interest in early selection studies.

The present study investigated different levels (S1: 100% of field capacity- Control S2: 50% of field capacity-moderate stress; S3: 0% of field capacity-severe stress) of drought stress on oxidative damages and variations in antioxidants in the two bean varieties Bn-16 (drought-sensitive), Bn-150 (drought-tolerant) to elucidate the antioxidative protective mechanism governing differential drought tolerance. The shoot fresh weight, shoot height, leaf number and area, RWC were reduced with different level of drought stress. However this reduction clearly occurred in Bn-16 (sensitive). Antioxidative enzyme activities, such as superoxide dismutase, catalase, ascorbate peroxidase and glutation reductase, had a greater increase in tolerant genotypes (Bn-150) than in sensitive ones (Bn-16). The level of lipid peroxidation was measured by estimating malondialdehyde content. Lipid peroxidation increased with increasing drought conditions in all genotypes, although Bn-150 was the least affected when compared with the other genotype. Total phenolic and flavonoid content increased in bean genotypes under S2 and S3 conditions. The highest total phenolic and flavonoid contents were attained in Bn-150 subjected to S3 treatment. These results indicated that an antioxidant defence system, osmolytes (such as proline), and secondary metabolites play important roles in common bean (Phaseolus vulgaris L) during drought stress and recovery.

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.

Grafting in vegetables is a method that has been commonly used in recent years, not just for the treatment of soil borne diseases and pests, but also to facilitate higher abiotic stress tolerance under conditions such as salinity. Herein, it was aimed to determine if the salt tolerance of two salt-susceptible melon genotypes, SCP-1 and SCP-2, could be improved by grafting onto TLR-1 and TLR-2, which are salt-tolerant melon genotypes, and Albatros commercial melon rootstock. The grafted plants were grown in plastic pots containing a peat: perlite mixture and exposed to NaCl at doses of 0 and 200 mM under greenhouse conditions. The salt-tolerant rootstock significantly diminished the damaging effects caused by salt stress via a reduction in the uptake of Na and Cl, which enhanced Ca and K uptake and micronutrition. Stress- induced activities of catalase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase were considerably higher in the grafted plants. The results showed that grafting salt susceptible plants onto the salt-tolerant rootstock improved the growth regulation. The salt tolerance of the grafted melon seedlings may have partially been the result of the decreased Na and Cl, and malondialdehyde contents and higher antioxidant enzyme activities.