Rhizospheric Addition of Hydrogel Polymer and Zeolite Plus Glutathione Mitigate the Hazard Effects of Water Deficiency On Common Bean Plants Through Enhancing the Defensive Antioxidants

Certainly, the adverse ecological conditions such as drought, salinity and heat are the distinctive abiotic stresses which can affect plant growth and productivity (Lasheen et al. 2023), threating the cultivable land areas (Alsamadany et al. 2022; EL-Bauome et al. 2022; El-Yazied et al. 2022). By 2050, it is anticipated that drought stress will cause serious plant growth problems for more than 50% of the arable lands (Vinocur and Altman 2005). Water shortage is one of the most restrictive factors on the cultivation and productivity of plants worldwide; thus, it affects the world’s food security (Tapia et al. 2022). Drought is the most threatening issue which resulted from climate change due to the reduction of rainfalls and water scarcity (Ahanger et al. 2021).

At plant cellular level, drought is associating with accumulation of reactive oxygen species (ROS), which reduce the electron transport chain activity (Hasanuzzaman et al. 2020). Different stresses are accompanied to excess ROS formation (Souri et al. 2019; Hatamian et al. 2020; Hadid et al. 2023). The hazard effects of ROS depend on deterioration of proteins, nucleic acids, membrane lipids and photosynthetic pigments (Zulfiqar and Ashraf 2021). Naturally, plants can defend themselves via enzymatic and non-enzymatic antioxidants by detoxifying ROS to alleviate stress impacts (El-Bially et al. 2018, 2022a; El-Metwally et al. 2021; Zulfiqar and Ashraf 2021; El-Mageed et al. 2022; Shahin et al. 2023). As a response to ROS stress, several osmo-regulators such as glycine betaine and proline are accumulated in plant cells (Shemi et al. 2021; El-Metwally et al. 2022a; Ramadan et al. 2023). However, suppression in photosynthetic pigments is proportionally linked to the potentiality of photosynthesis affecting crop productivity (El-Metwally et al. 2022b). Hence, water deficit reduced yield and quality (Abd–Elrahman et al. 2022; El-Bially et al. 2022b). As well, since drought causes stomata close, declines in photosynthesis assimilates and water–use efficiency were observed (Anjum et al. 2011; El-Metwally and Saudy 2021; Makhlouf et al. 2022). Moreover, the issues of drought could be ascribed to low availability of nutrients in soil while disturbance uptake and utilization by plant (Saudy and El–Metwally 2019; Mubarak et al. 2021; Salem et al. 2021). The negative impacts of abiotic stresses were reported in almost crop plant species such as faba bean (Ramadan et al. 2023), peanut (Saudy et al. 2020), sugar beet (Makhlouf et al. 2022), lettuce (Abd–Elrahman et al. 2022), sunflower (Saudy et al. 2021a, 2023a), canola (Shaaban et al. 2023a), and cereals (Saudy and Mubarak 2015; Salem et al. 2022; Saudy et al. 2023b; Saudy and El-Metwally 2023). Many strategies and approaches can be used to alleviate the drought stress on plants such as developing drought tolerant genotypes (Sprenger et al. 2016) and using soil amendments that enhance the soil water holding, i.e. hydrogel polymer and zeolite (Ozbahce et al. 2015; Čechmánková et al. 2021). Additionally, using exogenous antioxidants such as glutathione could be enhancer for the plant’s tolerance to drought stress (Maslennikova and Shakirova 2021).

It has been proved that manipulating the edaphic factors in favor of crop growth regarded as the crucial practice for boosting crop yield and quality (Saudy et al. 2021b, c, 2022; El-Metwally et al. 2022c; Ali et al. 2023; El-Bially et al. 2023). In this concern, hydrogel polymer, which can be made from synthetic or biological materials (Rico-García et al. 2020), has many uses for industrial purposes, pharmacy, cosmetics, medicine and agriculture. As for agricultural purposes, hydrogel polymer is categorized as a hydrophilic substance that can absorb and hold water for about 400-time of its dry weight, therefore, it can secure moisture into the soil to supply the plant roots with water. Thus, it can improve the soil properties by increasing the soil water retention, delaying the wilting point for the growing plants (Palanivelu et al. 2022; Turioni et al. 2021; Shankarappa et al. 2020), while decreasing the nutrients loss by leaching (Čechmánková et al. 2021). Moreover, it is characterized by the imbibition ability and swelling of its granules, capability of rewetting and nontoxicity (Turioni et al. 2021; Oladosu et al. 2022; Elshafie and Camele 2021).

Zeolite is an aluminosilicate mineral that is found naturally or synthesized using other minerals as raw sources (Belviso et al. 2017). Zeolite can absorb and hold water, without any conversion or change in its crystalline structure. Accordingly, zeolite can improve the soil properties by increasing the soil water holding capacity, cation exchange capacity and leakage rates (Mondal et al. 2021). Also, it can be utilized in agriculture production, since it acts as a chelating agent or slow-release fertilizer enhancing plant growth and productivity (Mondal et al. 2021; Hazrati et al. 2017; Sepaskhah and Barzegar 2010; Belviso et al. 2022).

Regarding glutathione, it is a non-enzymatic antioxidant that helps the plant to mitigate abiotic stress such as drought or salinity; because of its participation in detoxifying or scavenging ROS and reactive nitrogen species (RNS) (Hasanuzzaman et al. 2017). Glutathione consists of three amino acids; glutamine, cysteine and glycine. It enhances the osmoregulation and water status in plant cells, the photosynthesis process, and the plant’s physiological performance. Besides, glutathione shares with ascorbate, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase at the ascorbate glutathione pathway in plants (Hasanuzzaman et al. 2019). This cycle comprises several enzymatic antioxidants that work on scavenging the ROS. Accordingly, the exogenous application of glutathione to plants grown under abiotic stress is a novel approach to alleviate the drought stress on the plants (El-Beltagi et al. 2020; Koramutla et al. 2021).

Little studies related to the interactional effect of hydrogel polymer, zeolite and glutathione on common bean growth and antioxidant enzymes under water shortage conditions are available. Based on their advantages, the current work hypothesized that water-holding materials and glutathione could effectively interact for mitigating the hazards of drought against common bean. Therefore, this study aimed to assess the influence of water-holding materials (hydrogel polymer and zeolite) in combination with glutathione supply on physiological status, growth and productivity of common bean plants grown under water deficit stress.

Obviously, water deficit had negative effects on vegetative growth, chlorophyll content, yield and quality attributes and the mineral content of common bean plants. Previous studies pointed out similar trend in various vegetable crops such as cauliflower and potato (Ahanger et al. 2021; EL-Bauome et al. 2022; El-Yazied et al. 2022; Tapia et al. 2022). While both soil amendements and spraying of GSH, significantly increased the vegetative growth attributes and SPAD values, yield and quality attributes, the mineral content of leaves and pods as compared with control. The findings of the beneficial role of GSH agree with those reported by Zhang et al. (2022) on mulberry, El-Beltagi et al. (2020) on chickpea, Maslennikova and Shakirova (2021) on wheat. Also, the obtained results of soil amendments are in good accordance with previous researches implemented under drought stress on various crops including common bean (Ozbahce et al. 2015), green pea (Youssef et al. 2018), Aloe vera L. (Hazrati et al. 2017), tomato (Ju et al. 2022), olive (Lopes et al. 2022) and rice (Sepaskhah and Barzegar 2010).

Drought is one of the most significant environmental factors leading to dramtical declines in commercial crop production worldwide. Lack of water can affect crop development features, photosynthetic parameters, nutrient absorption, and yield production (Shaaban et al. 2023b). Drought stress affects various processes in the plant; sincxe it decreases the transpiration rate; consequently, the nutrients transport from the roots to the aerial parts of the plant (Griffiths and Parry 2002). Also, drought conditions significantly reduced the water potential of leaf and relative water content of the plant tissues (Sprenger et al. 2016; Diaz-Valencia et al. 2021; Seleiman et al. 2021), thereby causing toxicity to plant cells at severe drought conditions (Meher et al. 2018). Furthermore, drought conditions make osmotic imbalance in plant cells, exposing the plant to stress that increase the ROS, which increase the oxidative damage of the chloroplast, in turn, ATP synthesis obstructed (Ullah et al. 2017). This imbalance also leads to a decline in stomatal conductance that obstclate CO₂ intake causing increment in photorespiration and decrement in carbohydrates accumulation (Hasanuzzaman et al. 2017; Cornic 2000). Also, the excessive accumulation of ROS and RNS which is due to electron leakage from complex I and IV of the electron transport chain in the mitochondria resulting in disturbance in the mitochondrial respiration (Turk and Genisel 2020; Zhao et al. 2019). Hence, accumulation of ROS severely resulting in cell lipid peroxidation and damage the plant cell membranes and components (Ibrahim et al. 2020; Tiwari et al. 2021; Chaves et al. 2003; Anjum et al. 2017). Accordingly, the plant growth, development and productivity were negatively influenced by water deficit.

Concerning the soil amendments, the hydrogel polymers have roles at increasing soil water and nutrient retention, hydraulic conductance and water availability in rhizosphere to plants (Seleiman et al. 2021). Also, the evaporation from hydrogel treated soil decreased as compared with hydrogel non-treated soils (Saha et al. 2020). Further, hydrogel polymers improve the fertilizers performance in soil (Elshafie and Camele 2021). Consequently, the vegetative characters were enhanced mainly number of leaves and leaf area, leaf relative water content, and leaf dry weight (Tomášková et al. 2020), leading to enhancement of photosynthetic rate and nutritional status of plants as a result of increasing the uptake of micro and macro elements (Oladosu et al. 2022; M’barki et al. 2019). Subsequently, the yield attributes were enhanced by applying hydrogel polymer to soil (Fig. 4), and the yield quality (Fig. 5 and 6). Furthermore, it has been found that the hydrogel application increased the proline content at different drought sensitive and tolerant tree species under water shortage conditions, that acts as antioxidant which alleviates the drought stress on plants (Tomášková et al. 2020).

As for zeolite, it has been found that zeolite ameliorates the water retention and the water availability for plants (Hazrati et al. 2017). Also, it is considered to be a chelating agent since it acts as chemical sieve that blocks some ions while allows passing for others (Gholamhoseini et al. 2012). According to its physical and chemical properties, it enhances the cation exchange capacity of soil, decreases the nutrients leaching (Gholamhoseini et al. 2012) and supplies the plants with nutrients, i.e., potassium (Szatanik-Kloc et al. 2021; Chatzistathis et al. 2022). Thus, the beneficial effect of zeolite for alleviating drought stress on plants had been reported (Mondal et al. 2021; Ibrahim and Alghamdi 2021). The vegetative growth (Hazrati et al. 2017; Ju et al. 2022) and photosynthesis process (Lopes et al. 2022) of plants were enhanced as treated by zeolite. As a result of the enhancement of vegetative growth attributes and chlorophyll content, the yield characters and quality attributes were significantly enhanced.

Regarding glutathione foliar spraying, it is clear from results that the application of GSH significantly enhanced the vegetative growth characters, SPAD values, yield and yield quality under all irrigation levels. These increments associated GSH supply under drought might be attributed to its protective action as an antioxidant, while enhancing the osmoregulation and water status in plant cells and regulating various metabolic functions (Nahar et al. 2015; Chen et al. 2022). Not only GSH regulates the genes expression and encoding transcription but also regulates the signaling pathways by modifying the protein components via S‑glutathionylation and/or S‑nitrosoglutathione-mediated protein S‑nitrosylation (Koramutla et al. 2021; Koh et al. 2021). Hence under drought stress, the expression of DREB1 (dehydration-responsive element binding) was upregulated as well as P5CS ({Delta} 1‑Pyrroline-5-Carboxylate Synthetase) gene expression which is responsible for proline production, whereas the DHN5 and WZY2 (dehydrin) genes are correlated to dehydrins production in wheat plants (Vuković et al. 2022). Glutathione works as substrate at glutathione peroxidase (GPX) and glutathione S‑transferase (GST), hence GPX works at ROS detoxification, whereas GST is responsible for xenobiotic detoxification (Hasanuzzaman et al. 2017). Also, S‑nitrosoglutathione (GSNO) plays an important role in nitric oxide signaling. While the glyoxalase system comprises glyoxalase I (Gly I) and glyoxalase II (Gly II) enzymes, this system is responsible for detoxifying of cytotoxic and oxidative stress creator methylglyoxal (MG), where Gly I uses GSH at MG detoxification and signaling (Hasanuzzaman et al. 2019; Laxa et al. 2019). MG at high levels is a toxic compound that suppresses plant growth, development, and metabolic processes; seed germination, photosynthesis, increasing ROS in plant cells indirectly by reducing the available glutathione (GSH) concentrations which is a strong non-enzymatic antioxidant and impairing the function of antioxidant enzymes (Hasanuzzaman et al. 2017; Hoque et al. 2016). In addition, glutathione participates at the ascorbate-glutathione pathway which plays role at ROS detoxifying (Maslennikova and Shakirova 2021). Moreover, the increments in the vegetative characters and yield owing to GSH application could be ascribed to improved nutritional status of plants, since GSH stimulates the mineral content at the plant under all irrigation regimes by its role of ROS detoxifying. Accordingly, the application of glutathione enhanced common bean growth, yield and quality, nutritional status of plants grown under drought conditions.

Commonly, findings of the current work could introduce a significant approach which can be adopted to induce drought stress tolerance in common bean plants using soil amendments that enhance the soil water holding, i.e., hydrogel polymer and zeolite, in addition to foliar application of glutathione as an antioxidant defender.

The findings of this current research could be clearly elucidate the significance of using soil amendments (hydrogel polymer and zeolite) and glutathione under different irrigation regimes for enhancing vegetative growth characteristics, plant pigments, yield and yield quality attributes. Briefly, the combination of hydrogel polymer and glutathione under well-water exhibited the highest significant values of the vegetative growth, leaf greenness, yield and its quality, mineral content of leaves and pods, while the lowest significant values of antioxidant enzymes activity were noticed. The superior influence of combination between glutathione and soil amendments specially the hydrogel polymer was crystal clear, not only under the well-watered condition but also under the moderately water-stressed and severely water-stressed conditions. Therefore, common bean growers are advised to apply hydrogel polymer plus glutathione whether with water abundance or water deficiency to secure high yield and quality. However, further investigations using the advice molecular techniques are needed for understanding accuretly the role of soil amendments plus glutathione in increasing the yield and inducing varied signaling pathways in common bean plants under water shortage conditions.