Phytohormones are considered plant-protecting hormones under abiotic stress conditions. Different phytohormones are well-known management strategies, which act as stress-relieving bioactive compounds in vegetable crops (Fahad et al., 2015; Altaf et al., 2022a). The exogenous spray of numerous phytohormones can reduce the drought and salinity stresses and also improve the plant defense mechanism focusing on sustainable production. Fascinatingly, phytohormones are more effective for the reduction of challenges that occur from stressful conditions at any growth or developmental phases even from germination to plant senescence. These hormones are contributing to numerous signaling and transduction pathways through hormonal reception and regulatory actions (Hu et al., 2012). The membrane receptors, ionic networks, reactive oxygen species (ROS) indications, and mitogen-activated protein kinase (MAPK) indications are noticeable to numerous fundamental utilities in the synchrony by phytohormones to cope with the negative effects of abiotic stress. Understanding the interactive mechanism of phytohormones and transcriptomics can be effective for the development of tolerant germplasm of vegetables (Diao et al., 2015; Mangal et al., 2022). Modulation of physiological and photosynthetic pigments was found to be helpful for an increase in plant yield growing under water stress and saline conditions. The susceptible germplasm can also become higher yielding by sufficient use of phytohormones based on genetic makeup and climatic conditions of the characterized germplasm, as reported by Forni et al. (2017). However, the impact of phytohormones on the regulation of secondary metabolites and other signaling molecules needs further investigation for better understanding. For the development of tolerant germplasm, traditional breeding ways are time-consuming and not specific. However, the application of phytohormones is more effective for the alleviation of abiotic stress tolerance.

Plants growing under field conditions could be exposed to multiple stresses, which can damage the crops’ yield (Glick, 2012). Severe climatic conditions in summer, irregular nutrition management, and unavailability of irrigation water are causing stunted growth and poor crop yield. Sustainable agricultural crop production is drastically affected by numerous biotic stresses (such as insects, pests, and disease) and abiotic stresses (like drought, salinity, temperature extremes, humidity, light, ultraviolet radiations, mineral nutrition deficiencies, and heavy metals) (Akram et al., 2017; Shakoor et al., 2017). Drought and salinity are considered more destructive conditions, extensively affecting growth, developmental stages, and yield. Plants can change their defense system against stressful conditions to regulate metabolism, growth, and development (Ahmad et al., 2008). Vegetable crops are potentially growing under diverse environmental conditions by natural acclimation, as well as numerous adaptation strategies. However, these approaches may not be sufficient to reduce losses from variations in climate change (Shahid et al., 2021; Zhang et al., 2022a). The severity of abiotic stress is mainly based on the type of species and intensity and duration of stress (Zhang et al., 2022b). Stressful conditions cause variations in plant physiological and biochemical processes, either reversible or irreversible. However, these constraints affect vegetable crops primarily, which are susceptible to abiotic stress (Parveen et al., 2020). Presently, vegetable crop demand is higher; therefore, it is necessary to develop some excellent approaches or tolerant germplasm to tackle the severity of drought and salinity stresses. Drought and salinity stresses are critical global concerns and harm the sustainable production of crops. Irrigation water resources are depleting due to climate change, urbanization, and industrialization (Gruda et al., 2019). Soil salinity is also increasing, mainly due to irrigation with poor-quality and brackish water. The unavailability of quality water in various regions is causing salt accumulation in the soil, which further translocates toward the root zone of vegetable crops. It has been estimated that approximately 20% of global land is negatively affected by salt extremes (Forni et al., 2017).

Vegetables are considered an essential source of the human diet because they are rich in dietary fibers, vitamins, antioxidants, and minerals. Their consumption is also due to good taste, excellent texture, and religious value (Gamalero and Glick, 2022). Global vegetable production in 2020 increased by nearly 66%, from 447 to 1,130 Mt (FAO, 2021). Farmers are investing considerable efforts in improving vegetable production and nutritional aspects under stressful environments (Gruda et al., 2019). The severity of drought and salinity is mainly based on different climatic constraints like the distribution of solar radiation, the need for evapotranspiration, and the retention of soil moisture content (Sabir et al., 2022). Hence, numerous agricultural practices and breeding approaches can be employed for the alleviation of tolerance in vegetable crops against drought and salinity.

Plant researchers urge sustainable management practices to increase vegetable production under drought and salinity stresses (Ahmad et al., 2010; Checker et al., 2018). The exogenous application of phytohormones is a more promising approach to cope with the adverse effects of drought and salinity for sustainable vegetable production. The involvement of phytohormones is attracting much attention from plant researchers due to their multifunctioning behavior against drought and salinity stresses. However, their utilization is still limited in vegetable crops growing under drought and salinity. Therefore, the present study elaborates on the utilization of phytohormones in vegetable crops under drought and salinity stresses. Deep insights into physiological, biochemical, and molecular basis were also explored in the vegetables to cope with the adverse effects of drought and salinity.

Vegetable production is low in different growing areas due to water deficit and salinity. Restricted growth and low yield are due to the unavailability and shortage of water and excessive salt accumulation in the root zone of plants. The higher uptake of Na⁺ through roots by xylem vessels resulted in restriction in the uptake of nutrients and minerals necessary for sufficient growth and yield (Maksimovic and Ilin, 2012). Salinity, sodicity, and water stress revealed adverse effects on the growth, yield, and quality of vegetable crops. Higher accumulation of salts disturbed the soil structure, texture, porosity, and permeability of water, which ultimately reduces the productivity of vegetable crops (Malhi et al., 2021). Soil provides better anchor and acts as a reservoir of mineral nutrients necessary for better growth, development, and yield. Therefore, the development of mechanistic approaches is needed to minimize the damaging effects of drought and salinity in vegetable crops. Drought and salinity affect vegetable crops, causing restriction in growth with poor yield (Hossain et al., 2022). Drought stress and excessive Na⁺ accumulation are causing a disturbance in the metabolism of vegetable crops. Moreover, the osmotic potential of plants is also adversely affected due to drought and excessive salt accumulation in different plant cells and compartments (Zaidi et al., 2015). Alterations in metabolism and disturbances in osmotic potential are the leading causes of restricted growth and low yield and sometimes complete or partial death of a plant (Neha et al., 2021).

In addition to supporting signaling pathways, endogenous plant hormones are critical in the response to drought and salinity. Phytohormones play a major role in mediating how plants respond to osmotic adjustment under stress conditions. Small signaling molecules called phytohormones have a significant impact on almost every aspect of the development of plants. The methods of action taken by different hormones for various activities may be very different. Furthermore, it is well recognized that even a single hormone can have an impact on a wide range of cellular and developmental processes or that multiple hormones can regulate a single function concurrently. Phytohormones protect and control plants from biotic and abiotic stresses. As a result, phytohormone application aims to expand crop stress research in the future (Ahmad et al., 2008).

Drought and salinity stress decrease the uptake of Ca²⁺ and K⁺ in vegetable crops, which is the primary reason why nutritional imbalances occur in plants. Plant physiology and morphology are also affected by numerous stresses and thus are susceptible to drought and salinity stresses (Rodrıguez et al., 2005). The initial response of vegetable plants under drought and salinity is the dropping of leaves or the initiation of leaf senescence. After that, a reduction in fresh and dry weights may also be considered an early response of plants growing under water shortage and salinity stress conditions (Zhu, 2002). The decline in fresh and dry weights ultimately reduces the plant yield. Yield reduction is evident in vegetable crops growing under drought and salinity stresses (Alian et al., 2000). However, a reduction in yield can also be a responsive mechanism, especially in aerial plant parts (Sharma et al., 2011) ( Figure 1 ).

Plants have been categorized into two main groups, halophytes and glycophytes. It has been reported that halophytes are more tolerant than glycophytes (Zhang et al., 2017). The potential of halophytes was much imperative, and higher survival and reproduction rates were observed as compared to glycophytes due to improved root architecture, regulation in stomatal conductance, balanced nutrition, improved metabolism, and distinctive genetic makeup (Gao et al., 2018). Halophytes can tolerate approximately 200 mM of NaCl because, at this level, glycophytes cannot survive. Furthermore, the halophyte group constitutes a 1% proportion of global flora, and the individuals of this group were grown naturally (Patane et al., 2013). Leaf growth, especially leaf area, is also considered an initial response in stressful conditions within plant cells and compartments. Numerous other signs include leaf scorching from tip and margins, yellowing and bronzing, leaf dropping of leaves, dieback in twigs, necrosis, blackening, and burning (Bernstein et al., 2004).

Different ion movements continue within plant organelles and compartments under normal conditions. Higher regulation of cytosolic K⁺ and Na⁺ ratio was recorded in the vegetable crops grown under favorable conditions (Zhu and Gong, 2014). Under salinity and drought conditions, ion balances are disturbed, and abnormal movements of ions continue until the availability of favorable conditions. Water-deficit conditions increased the accumulation of salts in the root zone (Sattar et al., 2021). Excessive Na⁺ in the root zone and its translocation to other plant parts are also improved. Na⁺ and K⁺ channels are also present in the xylem vessels. The discrimination of both ions is necessary, although both are similar in power to hydrated ions, and their discrimination is difficult for plants. However, some transporters of ions with high-affinity potassium transporters (HKTs) are more effective for the discrimination and movement of ions through xylem vessels in all plant parts. Furthermore, some proteins, such as integrated membrane proteins, are also involved in the regulation of solute movements within plant cells and compartments (Ahmad et al., 2008). Moreover, these transporters and proteins are specific for ion regulation; for example, some are specific for the discrimination of Na⁺ and others for the discrimination of K⁺. Hence, it has been reported that regulation of Na⁺ and K⁺ is necessary for sufficient plant growth, development, and yield of potatoes (Kamran et al., 2021).

Recently, vegetable crops are facing numerous biotic and abiotic stresses; however, a single abiotic stress is also sufficient for the drastic reduction in crop yield. The water shortage and excessive salt concentrations show a direct effect on the reduction in vegetable crop yield (Lin et al., 2006). Any plant parts, even underground or aerial parts, can be damaged due to low soil moisture levels and excessive salts (Li et al., 2022). Under stressful conditions, vegetable plants and their response to drought and salinity are mainly based on the type of species, cultivars, and even landraces. It has been studied that Cl⁻ ions are effective for the catabolism of numerous enzymatic and non-enzymatic activities, and these are also known as co-factors for the regulation of the photosynthesis process (Rodríguez-Delfín et al., 2011). The behavior of sensitive and tolerant germplasm of vegetable crops toward Cl⁻ is more different. The excess of Cl⁻ is toxic; however, Na⁺ is more toxic than Cl⁻. Numerous genes are also involved in regulating Cl⁻ produced in plants. Aquaporin has also been involved in the characterization of numerous genes that contributed to the regulation of Cl⁻ efflux, which has significant involvement in the sustainable production of crops.

Salt exclusion and excretion restrict the salt’s access to the xylem vessels of vegetable crops. The exclusion of salts like Na⁺ and Cl⁻ via roots revealed that the storage of Na⁺ and Cl⁻ in leaves is not at a toxic level (Andre et al., 2009). However, their increased concentration disturbed physiological mechanisms, further resulting in leaf drop (Sobhanian et al., 2011). Grafting will be successful in numerous vegetable families and species like Solanaceae and Cucurbitaceae. Rootstock and scion combination contributed to the avoidance of salt mechanism in vegetable crops (Colla et al., 2010). Excessive salts in the root zone further translocated toward other plant parts. However, salt translocation can be reduced and not transported toward leaves. The rootstock’s basal portion can absorb the salts (Giordano et al., 2021). Therefore, it has been distinguished that the rootstock and scion combination is most necessary for alleviating salinity in vegetable crops ( Figure 2 ).

Salt exclusion is a variety-specific character in vegetable crops, and the higher exclusion of salts is the capability of a specific variety. However, this mechanism does not reveal the tolerance mechanism in vegetable crops. The avoidance mechanism of drought and salinity is also based on the root architecture of vegetable crops. Zhang et al. (2019) reported that grafting improves plant performance under drought and salinity stress in tomatoes. Similarly, phytohormones could improve the Solanaceae vegetable crop performance.

Expression of genes related to drought and salts is a more imperative utilization for the development of tolerant germplasm. Different genes and their expression in agronomic crops are widely discussed in the literature; however, in vegetable crops, this molecular phenomenon is still in progress. Most functional markers are related to numerous genes involved in the stress tolerance mechanism of vegetable crops (Ahmad et al., 2008). Gene expression potentially contributes to the development of salt-tolerant germplasm. Characterization of drought- and salt-tolerant and susceptible germplasm is a prerequisite for the sustainable production of vegetable crops (Malhi et al., 2021). Wild germplasm had more significant variation in genetic makeup and novel alleles, which can be explored to develop salt-tolerant germplasm. Numerous resistant genes can be identified, and further genome editing and transformation can be helpful for the development of tolerant germplasm in vegetable crops (Malhi et al., 2021). However, the expression of genes can be regulated by exogenous and endogenous improvements of phytohormones for the increase of tolerance against stress drought and salinity. Phytohormones are involved in the upregulation of transcriptomics of ATPase. Moreover, they were also involved in the reduction of the expression level of PpATG for the regulation of numerous morpho-physiological and biochemical activities in cucumbers. Moreover, similar findings were also reported by Parveen et al. (2021) for the expression of genes related to the tolerance mechanism.

Different management approaches comprised of proteomics, marker-assisted selection, genome characterization, genome editing, genome mapping, quantitative trait locus (QTL) mapping, genomic editing, and genomic transformation are promising molecular bases for salinity and drought tolerance in vegetable crops (Saidi and Hajibarat, 2020). Furthermore, the molecular bases can be utilized for the backcrossing of genes present in wild species toward offspring or landraces. The first genome map was developed in the 1980s on potatoes in relation to sexual recombination regularities. Plant breeders have successfully characterized disease-tolerant genes in potatoes (Byun et al., 2007). Moreover, numerous economic traits were detected in potatoes. Furthermore, “NL25” is one of the functional markers with excellent capability to identify candidate genes related to tolerance characteristics of potato warts (Saidi and Hajibarat, 2020).

Phytohormones have the potential to enhance vegetables’ growth and development by interacting with numerous processes responsive to stressful conditions (Groppa and Benavides, 2008). Phytohormones have the capability to improve the defense system of vegetable crops growing under drought and salinity stresses. Plants activate their defense system against adverse climatic conditions for their survival (Choudhary et al., 2012). Therefore, supplementation of phytohormones boosts the immune system of plants growing under drought and salinity stresses. Plant defense system comprises the activation of enzymatic compounds (i.e., superoxide dismutase (SOD), peroxidase (POD), and catalases (CATs), non-enzymatic activities (i.e., ascorbic acid (AsA), phenolic content, and different sugars), osmolytes (i.e., glycine betaine (GB), ascorbate peroxidase (APX), and proline), and oxidative stress-indicating activities (ROS, malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) ( Table 1 ). Therefore, the impact of phytohormones on vegetable crops is imperative and needs more investigation on the molecular level to enhance plant tolerance (Diao et al., 2015).

In the present study, it has been explored that modulation of physiological and biochemical mechanisms is necessary for sustainable production of vegetable crops growing under drought and salinity stresses. Exogenous application of phytohormones is necessary for the improvement of vegetable growth, yield, photosynthetic pigments, minerals nutrient content, and defense-related characteristics. It has been concluded that phytohormones are necessary for the sustainable production of vegetable crops.

JC: conceptualization, literature survey, writing major original draft, and review structure. XP: literature survey, writing—review and editing, and figure designing. All authors contributed to the article and approved the submitted version.