Heat stress can cause a range of modifications at morphological and anatomical levels in plants such as scorching of leaves and stems, loss of leaves, inhibition in shoots and roots growth, shrinking of seeds, and damage to fruits. As a result of these alterations, it consequently lead to reduced crop productivity (Vollenweider and Günthardt-Goerg, 2005). In mungbean, heat stress causes many structural changes at morpho-anatomical level (Figures 3A–H). The different phases of reproductive stage such as pollen germination, loss of pollen viability, less pollen load on stigma, poor anther dehiscence, pollen sterility, and poor ovule viability lowers the crop yield (Kaushal et al., 2013). In a study by Kaur et al. (2015) on two mungbean genotypes (SML 832 and SML 668), similar results were observed in response to heat stress treatment. They also observed decrease in plant biomass (16%–19%), total number of pod set, seed yield (35%–40%), number of filled pods (32%–38%), and seed number (43%–47%), due to high temperature exposure.

Failure of ovule fertilization is often associated with plant productivity factors such as loss of pollen viability, loss of stigma receptivity and reduced pollen tube growth (Hurkman et al., 2009; Patriyawaty et al., 2018). Pollen becomes often non-viable before fertilizing the flower (Figures 3I,J). It is also reported that the higher ambient temperature reduces the stigma receptivity to pollen causing embryo abortion and poor seed set (Kaushal et al., 2013). Reductions in seed set per pod are reported to be correlated with the poor pollen tube growth and tropism defects (Zinn et al., 2010). Moreover, heat stress can directly damage cell membranes, leading to changes in their permeability. The heat stress can alter the microtubules organization which not only affect the elongation, differentiation, and expansion of cells but also negatively impacts the cytoskeleton structure (Rasheed, 2009; Bita and Gerats, 2013). In addition, heat stress also causes decrease in pod length, seed quality, seed size, and number of seeds per pod which ultimately reduces grain yield and quality in mungbean. Similarly, Sharma et al. (2016) reported that heat stress-induced oxidative stress caused chlorosis, leaf rolling, and leaf blistering in mungbean plants.

Several studies have confirmed the susceptibility of mungbean to rising temperatures (Jha et al., 2017). High-temperature stress can have drastic impacts on plant growth and development, as well as on different physiological activities (HanumanthaRao et al., 2016). For instance, mungbean may lose vigor due to extended exposure to high temperatures results in limiting seedling growth and development (Kumar et al., 2011; Devasirvatham et al., 2012). Heat stress can also result in negative impacts on vegetative growth, including leaf senescence, chlorosis, necrosis, burning, and abscission, reduced internode elongation, and suppression of root and shoot development (Kaushal et al., 2016; Sharma et al., 2016). Other effects of heat stress on mungbean include leaf curling, plant wilting, yellowing and blackening of leaves, reduction in plant height, reduced number of branches, and biomass (Kaur et al., 2015). Figure 2 and Table 1 illustrate the impact of heat stress on mungbean’s morphological and anatomical traits.

Heat stress can have several negative impacts on plant physiology, such as chlorophyll reduction, decreased photosynthesis, decreased transpiration, increased canopy temperature, and increased stomatal aperture (Schoffl et al., 1998; Kaushal et al., 2013). These effects can ultimately lead to reduced plant productivity. Additionally, heat stress can cause membrane damage, protein degradation, and altered metabolism in plant cells (Schoffl et al., 1998; Kaushal et al., 2013). Heat stress can also increase electrolyte leakage in plants due to altered membrane permeability by direct injuries, which affects the differentiation, elongation, and expansion of cells (Rasheed, 2009; Bita and Gerats, 2013). Further, structural alterations in chloroplast protein complexes and reduction in enzyme activity occur due to the initial impacts of thermal stress (Ahmad et al., 2010). Although a modest rise in ambient temperature generally promotes plant growth and development, it shortens the plant’s life span and results in a significant reduction in light uptake during the plant’s growth phase (Kalaji et al., 2016). Additionally, plant water status is a critical component of plant survival under heat stress. Plants try to normalize their canopy temperature through increased transpiration rate, and therefore, heat stress in combination with soil moisture stress proves to be most detrimental to the plant (Simões-Araújo et al., 2003). Unfortunately, most of the legume crops, including mungbean, are cultivated under rainfed conditions in tropical and sub-tropical regions. As a result, increasing global warming and adverse climatic conditions disrupt the monsoon seasons, resulting in uneven/less rainfall, which affects plant growth and development (Simões-Araújo et al., 2003). Heat stress can rapidly reduce tissue water content despite ample availability of soil moisture, similar to drought stress conditions, leading to a disruption in nutrient uptake from roots (Wahid et al., 2007). The drastic water loss due to high transpiration, particularly during the daytime, affects important physiological processes, ultimately resulting in reduced plant growth and development (Fahad et al., 2017). Heat stress can also reduce seed viability and lower plant and yield quality. Moreover, plants exhibit programmed cell death in some specific cells and tissues under heat stress (Anderson and Padhye, 2004).

In mungbean, the ideal temperature for growth and development is 28°C–30°C, and further every degree increase in temperature may reduce crop production by 35%–40% (Tzudir et al., 2014; HanumanthaRao et al., 2016; Sharma et al., 2016). Mungbean plant can thrive well up to 40°C of temperature, after which flower shedding begins (Zinn et al., 2010; Sita et al., 2017). Heat stress reduces leaf area and stomata openings which cause dramatic reduction in the carbon dioxide assimilation rate and photosynthesis during the vegetative stage of the mungbean (HanumanthaRao et al., 2016). The increase in carbon dioxide (CO₂) content also causes stomatal closure, which hinders photosynthesis in the mungbean. High CO₂ concentration along with high ambient temperature, proves more detrimental for mungbean growth and development (Reardon and Qaderi, 2017). In a study, CO₂ assimilation in mungbean was significantly reduced at 40°C, which had a direct impact on photosynthetic efficiency (Karim et al., 2003). High temperatures also reported to reduce the chlorophyll and carotenoid levels, as well as the chlorophyll stability index (Chand et al., 2018). A slightly higher temperature (36°C) temperature treatment on mungbean genotypes indicated that the exposure of plants to high temperature has greater adverse impact on leaf conductance at the pre-flowering stage than the blooming and grain filling stages, although high-temperature treatments had no effect on transpiration rate at any stage, but photosynthetic activity decreased at all three stages (Islam, 2015). Similarly, another study on three prominent mungbean varieties viz., MH 421, MH 318, and Basanti indicated reduction in chlorophyll and carotenoid content, as well as a decrease in chlorophyll stability index in response to high temperature (Chand et al., 2018). Under heat stress, sensitive genotypes (MH 318 and Basanti) showed higher losses in the physiological attributes stated above, whereas tolerant genotypes (MH 421) maintained high yield and physiological functioning (Chand et al., 2018). Evidenced from numerous studies it is found that Photosynthesis is highly sensitive to high temperatures (Sinsawat et al., 2004). Heat stress affects photosynthetic functions in mungbean by disrupting photosynthetic machinery, causing structural aberrations (particularly the thylakoid membrane) and alterations of chloroplast enzymes. Based on mungbean germplasm screening for heat responsive traits various important promising mungbean donors are identified (Table 1). Also, impact of heat stress on physiological processes in various crops is listed in Table 1 and Figure 1, Figure 2.

High temperatures have a significant impact on the metabolism and biochemistry of mungbean plants. Under heat stress, the formation of reactive oxygen species (ROS), such as hydroxyl radical, singlet oxygen, superoxide radical and hydrogen peroxide, increases, causing protein degradation, membrane damage, and enzyme inactivation, and hence increases oxidative stress (Liu and Huang, 2000). Long-term exposure to relatively high temperature stress can result in severe cellular injury or death, while at extremely high temperatures, this can occur in just minutes (Wahid et al., 2007). These injuries, coupled with a lack of water content, can cause a reduction in ion flow and plant growth, as well as an increase in the generation of toxic compounds and reactive oxygen species (Howarth, 2005). Some of the metabolic effects of heat stress on mungbean plants are briefly described in Figure 1 and Table 2.

In mungbean, high temperature especially >40°/30°C (max/min) reduces leaf water potential and increases oxidative stress resulting in growth suppression and chlorosis which is linked to reduced crop yield (Kumar and Wigge, 2010). High temperature stress can cause a considerable increase in hydrogen peroxide (H₂O₂) concentration in mungbean as well as in other plants, which could be due to a reduction in catalase activity by blocking catalase production which lowers the enzyme’s steady-state level because of high turnover rate (Scandalios et al., 1997). When plants are exposed to high levels of heat, they experience an oxidative burst (N, 1997) that can cause an increase in H₂O₂ (Levine et al., 1994; Baker and Orlandi, 1995). Antioxidant enzymes such as SOD and CAT become less active during heat shock, compromising the plant’s defenses and leading to increased levels of oxidant species (Willekens et al., 1995; Foyer et al., 1997; Polle, 1997). This can have a negative impact on cellular metabolism, resulting in high levels of harmful compounds like malondialdehyde and H₂O₂ that affect plant productivity (Bita and Gerats, 2013). Lipid peroxidation under aerobic conditions, is a natural metabolic process that can be affected by ROS, causing damage to the cell membrane and impairing its function (Blokhina et al., 2003). (Heath and Packer, 1968). The presence of malondialdehyde (MDA) is an indication of oxidative damage, and it is created by the lipid peroxidation of the cell membrane (Mandhania et al., 2006). It has been reported that high temperature stress on four mungbean genotypes (NCM 89, NM 20-21, NM 121-123, and NM 19-19) at seedling stage observed an increase in the levels of lipid peroxidation as there is a considerable increase in MDA concentration (Mansoor and Naqvi, 2013). Studies in seedlings of four mungbean genotypes have shown that an increase in temperature can cause an increase in lipid peroxidation, leading to decreased net photosynthesis, water use efficiency, stomatal conductance, total chlorophyll, and nutrient partitioning in sensitive genotypes. Additionally, heat stress can negatively impact assimilate partitioning and apoplastic to symplastic phloem transport, resulting in a decrease in carbohydrate buildup and viability of pollen grains in mungbean (Kaur et al., 2015; Taiz et al., 2015; Hanif and Wahid, 2018).

Seed shriveling in legumes is primarily linked to reduced synthesis of carbohydrates and storage proteins due to elevated temperature. The four enzymes viz., Adenosine Diphosphate Glucose Pyrophosphorylase, Starch Branching Enzyme, Starch Synthase, and Sucrose Synthase are crucial for the grain filling process (Taiz et al., 2015). In general Sucrose synthase plays in important role in grain filling (Basu et al., 2019), and temperature beyond a certain period affects the enzyme activities and lead to poor grain filling. Similarly, the functioning of Nitrate reductase is also diminished during heat stress, which is a most important enzyme of nitrogen (N) metabolism in plants. It catalyzes the reduction of inorganic N in the form of nitrate to organic form in translational process of proteins. Heat stress is known to adversely affect the nitrate reductase enzyme activity, which is more detrimental for leguminous crops affecting protein biosynthesis during grain filling and reproductive stages (Klimenko et al., 2006; Farooq et al., 2017). Heat stress also impairs the nitrogen-fixing activity of mungbean by restricting the production of root hair and infection thread (Bansal et al., 2014). Furthermore, heat stress reduces seed viability, plant and seed quality (Anderson and Padhye, 2004). The nutritional value of seed is impaired mainly due to adverse impact of heat stress on synthesis and accumulation of protein and carbohydrates (Taiz and Zeiger, 2010).

Increase in atmospheric temperature beyond a certain optimum point drastically reduces the plant growth and development as cellular processes require a specific temperature range. Plants have evolved with a great variability in their morphological adaptation as a part of survival mechanisms, such as early maturation, leaf rolling, and changing leaf orientation to cope up with the certain level of temperature deviations (Srivastava et al., 2012). However, these adaptation mechanisms are often associated with yield losses under high temperature in many crop plants (Adams et al., 2001; Rodriguez et al., 2008). Further rise in atmospheric temperature causes development of symptoms such as scorching of leaves and twigs, shoot and root growth inhibition, early onset of leaf senescence and abscission, and pod discoloration as an adaptation for plant survival. In response to heat stress, plant height is reduced in mungbean, which is specifically attributed to the disruption in cell elongation. This demonstrates that the mungbean plants exhibit the adaptation mechanism to respond heat stimuli. Certain important differences can be detected in the parameters like 100 seed weight, seeds/plant, pods/plant, seed yield, total biomass/plant, branches/plant, and plant height, etc. In mungbean as adaptation traits (Sharma et al., 2016) (Table 1). The reproductive phase of plant growth and development is highly sensitive to heat stress. To overcome certain level of higher temperature, plant deploy two very crucial mechanisms of plant defense viz. Dehydration of pollen grains and embryos, resulting in stress tolerance in the pollen grains, and prolonged dormancy in embryos under stressful conditions (Zinn et al., 2010). As a result, pollen and embryos remain viable under higher temperature, however, the magnitude of tolerance varies among genotypes. Therefore, these traits are considered as important for development of heat-tolerant mungbean varieties (Rainey and Griffiths, 2005).

In a study effects of heat stress on 41 mungbean genotypes for their vegetative and reproductive activities under controlled growing conditions was examined and a few tolerant lines for stress were identified (Sharma et al., 2016). A field study in New Delhi in the Kharif seasons of 2014 and 2015 was conducted to assess the impact of high temperatures on seven mungbean genotypes in a rain-fed environment, and various heat stress responsive morphological traits were identified (Chikukura et al., 2017). Night temperature rise is considered as more crucial for flower drop, as it is observed that under the higher temperature stress, the flower abscission is higher during the night as compared to the daytime (Solai et al., 2015). Under high temperature stress, plants maintain their metabolites level required for flower and pollen and anther development. According to Banon et al. (2004), the reduction of cell size and the closure of stomata can help to decrease excessive water loss and lead to increased stomatal density and enlarged xylem vessels in plants under heat stress. However, Shen et al. (2017) have noted that the anatomical changes in response to heat stress can vary among different species. Some of the important morphological, physiological, biochemical and anatomical responses of mungbean genotypes to heat stress tolerance are highlighted in Figure 1, Figure 2 and Table 2.

There are few studies on how high temperature stress affects stage-specific functional physiology in legumes from post-flowering to blooming. The reproductive stage is destined to be more impacted by and prone to temperature vagaries due to its delicate organelle constitution, even if heat stress sensitivity in plants changes with plant growth. Depending on the species and genotype, there are significant inter- and intra-specific variations that affect the response under heat stress (Sakata and Higashitani, 2008; Bita and Gerats, 2013).

The persistence of photosynthesis in plants when they are exposed to stress conditions is supported by the stay-green (SGR) trait, which is also known as delayed leaf senescence. The maintenance of photosynthetic activity in plants under stressful conditions is facilitated by the stay-green (SGR) trait, also referred to as delayed leaf senescence (de Souza Luche et al., 2015). Understanding the role of SGR in plants could lead to improved plant production and productivity (Thomas and Ougham, 2014). During grain filling, the SGR characteristic allows plants to continue photosynthesizing by creating a senescence pattern that increases the amount of sugar produced by photosynthesis (Pinto et al., 2016). According to recent research, SGR wheat genotypes demonstrated improved tolerance to high temperatures due to enhanced structural stability of the photosynthetic apparatus and lower accumulation of harmful reactive oxygen species (Tian et al., 2012). The cultivar “Mairaj-2008” has also demonstrated superior ability to grow under heat stress compared to cultivars that lack the SGR trait and are more susceptible to heat damage (Nawaz et al., 2013). Canopy temperature depression (CTD) could serve as a useful tool for selecting heat-tolerant genotypes based on observable differences in their traits (Mason and Singh, 2014). Studies have shown that lower canopy temperatures promote better yield potential in wheat exposed to elevated temperatures, and CTD is effective in mitigating heat stress in wheat (Amani et al., 1996; Fischer et al., 1998; Mason et al., 2013). Examination of stomatal behavior under stress conditions can be performed using a leaf porometer, which measures fluctuations in gaseous exchange rate that trigger stomatal opening (Chandra et al., 2017). High-yielding cultivars with fully opened stomata have increased transpiration rates, improved CO2 and water vapor diffusion, and enhanced photosynthetic efficiency (Condon et al., 2007).

Chlorophyll fluorescence (ChlF) is a non-invasive marker for photosystem II (PSII) quantum efficiency and can be used to assess early stress in plants, making it a useful tool for investigating plant heat stress tolerance (Sharma et al., 2014; Kalaji et al., 2016). Studies have found that genotypes with high ChlF values, such as the heat-tolerant line RRR46 of common bean, outperform other lines when exposed to heat stress, indicating their potential for future breeding programs (Stefanov et al., 2011). Membrane stability is another important physiological trait that can affect heat tolerance in plants, and higher membrane stability during grain filling has been shown to increase heat tolerance in wheat (Gupta et al., 2013; Ramani et al., 2017).

Flag leaf photosynthetic efficiency has also been found to play a role in heat stress tolerance in crops. For example, the wheat cultivar “Jimai22”showed increased yield under heat stress and demonstrated PSII stability and significant carboxylation activity (Feng et al., 2014). Heat-tolerant mungbean and lentil genotypes have also been found to exhibit better photosynthetic efficiencies under heat stress than heat-sensitive genotypes (Sharma et al., 2016; IG3263, respectively). Conversely, decreased cellular thermostability in rice has been linked to potential reductions in crop output (Maavimani and Saraswathi, 2014). Overall, physiological traits such as ChlF, membrane stability, and photosynthetic efficiency can provide important insights into plant heat stress tolerance and can be used to identify promising genotypes for breeding programs. A comprehensive list of mungbean genotypes based on physiological traits under heat stress tolerance is provided in Table 1.

The traditional theme of research on legume reproduction has tremendously focused on vegetative stage of the plants rather than their physiological and molecular mechanisms underlying legume crop reproductive heat tolerance (Lin et al., 1984; Valliyodan and Nguyen, 2006; Kumar, 2012; Sita et al., 2017). However, recent studies have shown a growing interest in understanding these mechanisms (Devasirvatham et al., 2012; Kaushal et al., 2013; Sita et al., 2017; Patriyawaty et al., 2018). Despite this, there is still a lack of knowledge regarding the specific physiological and molecular mechanisms that allow legume crops to be resilient to heat stress during the reproductive stage (Devasirvatham et al., 2012; Kaushal et al., 2013; Sita et al., 2017; Patriyawaty et al., 2018). One possible explanation for this lack of understanding is that many legume cultivars are difficult to transform genetically, which limits the availability of transgenic evidence (Young and Udvardi, 2009; Song et al., 2013). However, on the basis of current research on other crop groups, particularly cereals, it is possible to suggest physiological and molecular explanations for legumes’ ability to withstand heat stress (Devasirvatham et al., 2012; Kaushal et al., 2013; Sita et al., 2017; Patriyawaty et al., 2018).

Plants have evolved with a number of biochemical adaptation mechanisms that allow them to tolerate high temperature stress, for example, secondary metabolites, ROS scavenging system and heat-shock proteins (HSPs) (Nakamoto and Hiyama, 1999; Sakamoto and Murata, 2002; Wahid et al., 2007; Mittler et al., 2012). Plants use both non-enzymatic and enzymatic ROS scavenging defense mechanisms to combat ROS production. Non-enzymatic antioxidants such as glutathione (GSH) and ascorbic acid (ASC) collaborate with enzymatic antioxidants such as ascorbate peroxidase (APX), Catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), and glutathione reductase (GR) to maintain high antioxidant levels required for plant heat tolerance. (Suzuki et al., 2012; Awasthi et al., 2015). Isoprenoids, flavonoids, and carotenoids are secondary metabolites that inhibit peroxidase activity and promote high-temperature stress tolerance (Havaux, 1998; Loreto et al., 1998; Rivero et al., 2004). Chickpea grown under high-temperature stress at 35/25 and 45/35°C (day/night, 12 h/12 h) conditions exhibited increased levels of antioxidants such as proline and glutathione (Kumar et al., 2011). The non-enzymatic and enzymatic antioxidant pools are the most efficient and prominent defense mechanisms used by plants. Antioxidants with low molecular weight decrease oxidants without causing significant pro-oxidant activity.

The enormous generation of ROS occurs during heat stress which destroy proteins, lipids, nucleic acids, and carbohydrates (Bita and Gerats, 2013). Mungbean plants can protect themselves from ROS by activating various types of non-enzymatic and enzymatic defensive mechanisms in different cells in plants (Bita and Gerats, 2013). In an experiment under field conditions for heat stress, out of forty-one mungbean genotypes, only a few were found to be heat-tolerant viz., EC693357, ML1299, EC693369, Harsha, and EC693358 which suffered less oxidative damage than heat sensitive mungbean genotypes (Sharma et al., 2016) and when compared to susceptible genotypes, there was increased APX activity in heat resistant genotypes. However, the activity of CAT was increased in both heat-resistant and heat-tolerant genotypes (Sharma et al., 2016). As a result, mungbean genotypes that can withstand under heat stress during reproductive stages could be chosen for screening growth and productivity analysis. Some supplements, such as Ca, K, Mg, and N have been shown to reduce the harmfulness of ROS in plant cells by increasing anti-oxidants such as POD, SOD and CAT (Waraich et al., 2012). Mungbean genotypes can be chosen based on the quantity of enzyme expression, with stress tolerant genotypes having more prominent activities than sensitive genotypes for breeding stress tolerant mungbean cultivars (Kumar et al., 2013).

Aside from the anti-oxidative system, accumulation of various appropriate protective osmolytes such as sugar and their derivatives (polyols), ammonium-based products, proline, and some compounds of sulphonium-based derivatives have been shown in the protection and/or repair of molecules and structures damaged by ROS, as well as in ROS sequestration (Sairam and Tyagi, 2004; Miller et al., 2007). As a result, osmotic adjustment is considered as one of the most promising mechanisms for drought and heat which can be accomplished by accumulating appropriate solutes (e.g., glycine betaine and proline) in protoplasm (Chaves et al., 2003; Bartels and Sunkar, 2005). Proline is one of the prominent osmo-protectant, which also play a crucial role in cellular homeostasis. It also acts as a signaling molecule in triggering specific gene expression, in cell proliferation or cell death, and to alter mitochondrial functions. These are crucial processes for plants’ recovery after stress. Certain natural combinations of osmolytes are formed under abiotic stress conditions such as salt, drought, and heat (Hare et al., 1998; Sakamoto and Murata, 2002). Plants may protect themselves by the accumulation of these solutes in order to increase the tolerance up to certain circumstances. These osmolytes help in increasing the stability of membrane bilayer and proteins. Defensive molecules such as flavonoids, anthocyanin, and plant steroids have been recognized as secondary metabolites that contribute to heat stress tolerance in plants. In response to heat stress, plants also increase their levels of several major phytohormones including ethylene (ET), salicylic acid (SA), and abscisic acid (ABA) to enhance their tolerance. Evaluation of these plant hormones in response to heat stress involves measuring various biochemical and physiological parameters, as well as assessing growth regulating parameters such as photosynthesis and biomass. Additionally, other hormones like auxin, gibberellins (GAs), cytokinins, abscisic acid, brassinosteroids (BRs), and jasmonic acid (JA) have been identified as contributing to heat stress tolerance in plants, as noted by various studies (Peleg and Blumwald, 2011; 2011; Mittler et al., 2012; Zhou et al., 2014; Dobrá et al., 2015; Xia et al., 2015).

Plants possess an adaptive mechanism to manage heat stress via the production of stress proteins like heat shock proteins (HSPs). These HSPs act as molecular chaperones and assist in activities like protein folding, translocation, aggregation, and degradation in both regular and stressful environments (Vierling, 1991). When subjected to sudden or constant temperature variations, plants increase their HSP production (Schoffl et al., 1998; Nakamoto and Hiyama, 1999), highlighting the critical nature of HSPs when it comes to temperature stress across all species (Vierling, 1991). Plants in dry and semi-arid regions can synthesize and store HSPs in large quantities. HSPs are only present during specific developmental stages like pollen formation, germination, fruit maturation, and embryogenesis. These proteins protect other proteins from denaturation that could be caused by high temperatures. In sensitive organs and tissues where HSPs accumulate quickly, they can safeguard the metabolic system of the cells, which makes them crucial in a plant’s stress response and overall survival. Numerous research studies have established a close relationship between the development of heat tolerance and the synthesis and buildup of HSPs. An instance of this is the elevated expression of HSP68, which is typically expressed constitutively in mitochondria, when potato, maize, tomato, soybean, and barley cells were placed under heat stress (Neumann et al., 1993). HSP70, extensively studied, is believed to partake in several functions, including but not limited to the folding or assisting of proteins, translocation, protein translation, proteolysis, inhibition of aggregation, as well as the restoration of denatured proteins (Zhang et al., 2005). Many plant species necessitate the induction of HSP70 for heat tolerance of cells and tissues post heat stress. Additionally, HSP101 has been deemed vital (Schoffl et al., 1998). Furthermore, different tissues within the same plant manifest diverse abilities to produce specific proteins at 40°C and the magnitude and duration of the synthesis also differ. Five different types of heat-stress protein/chaperone families are reported; these are HSP100, HSP90, HSP70, HSP60 and the small heat-stress proteins (sHSPs) family (Wang et al., 2004), that play an important role in heat-stress mitigation, including protecting native proteins against denaturation.

Along with development of tolerant mungbean genotypes integration of heat stress mitigation strategies through appropriate agricultural practices will have greater impact on sustaining the mungbean production amid rising global temperature. Agricultural practices such as timely sowing of crop, selection of early short duration genotypes to escape peak heat stress period, seed priming to enhance the seed vigour and initiate heat tolerance defense mechanisms, irrigation management to enhance water use efficiency and maintain plant water potential, mulching and enhancing organic material to enhance soil water retention and reduce soil temperature. Mungbean sown during summer/spring season, particularly in northern part of India, face more threat of heat stress during later stage of crop growth (HanumanthaRao et al., 2016). To overcome the terminal heat stress, early maturing mungbean cultivars with early seedling vigour are very crucial for sustaining mungbean production. Majority of mungbean cultivars matures in 60–70 days, however, the evaluation of mungbean collections reveals availability of mungbean germplasm which matures within 50 days of sowing (Gayacharan et al., 2020). Seed priming is another promising tool for induction of artificial stress memory response in terms of accumulation of secondary metabolites, antioxidants, improved water plant water potential, etc. (Ahmad et al., 2021; Chakraborty and Dwivedi, 2021; Tamindžić et al., 2023). Utilization of heat tolerant mungbean cultivars may further help in mitigating impact of heat stress in mungbean cultivation. Mungbean cultivars such as Pusa Vishal, SML 668, IPM 99-125, and few more listed in Table 1 are helping in sustaining mungbean cultivation during the summer/spring season in northern parts of India.