Abstract
Soybean is a very important food legume because of its high protein and oil concentrations. However, soybean is vulnerable to drought stress, which has become more severe and occasional in many regions worldwide. To alleviate drought’s influence, the application of certain agents is increasingly gaining attention as it is economically affordable and practically applicable. Acetic acid (AA) is, by far, one of the cheapest agents that are reported to have potential benefits against drought; however, no accurate data on its influence on soybean genotypes differing in their drought tolerance are published. An experiment was conducted in a controlled environment to evaluate the effects of AA on the morpho-physiology of two soybean (Glycine max (L.) Merr.) genotypes: drought-tolerant ‘Speeda’ and drought-susceptible ‘Coraline.’ Chlorophyll-a and total carotenoids, stomatal conductance, and specific leaf area of both soybean genotypes decreased under water deprivation conditions. However, AA application enhanced these traits significantly. Drought reduced the optimal and the actual photochemical efficiency of PSII of ‘Coraline,’ but not ‘Speeda.’ The application of AA could not enhance the relative water content of both genotypes. Root and shoot morphology were negatively influenced by drought in both genotypes; however, AA helped in restoring these traits in ‘Coraline,’ but not ‘Speeda,’ indicating that AA application might be more beneficial in the case of drought-susceptible soybean genotypes.
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Introduction
For thousands of years, soybean (Glycine max (L.) Merr.) has historically been used as a forage and a major protein and oil crop. Soybean is one of the most important food legumes due to its high protein (about 40%) and oil (about 20%) concentrations, as well as carbohydrates and minerals (Maleki et al. 2013). In the last four decades, soybean production has remarkably grown (Müller et al. 2021), however, to meet the expanding human population’s need for plant protein, soybean production will have to increase by 70% over the next few years (Godfray et al. 2010; Tilman et al. 2011).
Droughts are anticipated to become even more often and severe in many regions of the world, putting significant strain on global agricultural supply (Zia et al. 2021; Gáspár et al. 2022). According to Wei et al. (2018), soybean yields can drop by more than half under dry or drought conditions, resulting in significant losses incurred for agricultural producers. Drought stress is a critical nonbiological force that can influence the morphological, physiological, and molecular processes such as photosynthesis immediately and extensively (Nabi et al. 2021), in addition to other light-related physiological parameters such as chlorophyll content and fluorescence (Basal et al. 2020). It also reduces leaf area, biomass output, and stem extension, affects cellular turgor pressure, inhibits water uptake and content, and impairs gas exchange efficiency and nutrient uptake, according to numerous studies (Khatun et al. 2021; Hussain et al. 2018; Dos Santos et al. 2022). Drought stress can also promote the formation of reactive oxygen species (ROS) and membrane lipid peroxidation, resulting in poor plant growth and, in extreme situations, death (Nadeem et al. 2019). Considering the impact of drought stress on plants becomes crucial as a result of these concerns, as this knowledge may be utilized to enhance irrigation scheduling techniques, lowering drought-related variations in food output. When germinating seeds are subjected to severe stress, restrained germination is likely (Swigonska and Weidner 2013).
Treating plants with cost-effective sensing molecule(s) (SMs) has garnered considerable attention for its potential to alleviate drought in a variety of agricultural crops, including soybean. Additionally, it was found that ROS play a major part in controlling stomatal closure to maximize irrigation efficiency (Huang et al. 2009). Chen et al. (2016) found that foliar application of hydrogen sulfide (H2S) enhanced the water potential and osmolarity of Spinacia oleracea leaves under drought stress by lowering malondialdehyde (MDA) levels. Furthermore, at low concentrations, H2S is known for its critical part in the regulation of physiological mechanisms in plants, including germination of seeds (Li et al. 2020), root development (Hu et al. 2020), stomatal conductance (Lisjak et al. 2011), photosynthesis (Chen et al. 2011), and toleration of abiotic and biotic stresses (Shi et al. 2015). Ethanol also has appeared as an outstanding example of organic SMs that have already demonstrated promising results in alleviating the harmful effects of various abiotic stresses in rice (Kato-Noguchi et al. 2001), soybean (Das et al. 2022) and Arabidopsis (Nguyen et al. 2017).
Acetic acid (CH3COOH), commonly known as ethanolic acid, is the most abundant carboxylic acid found in lignocellulosic hydrolysates. A dilute (roughly 5% by concentration) acetic acid solution is obtained through fermentation and oxidation of naturally occurring carbohydrates (Brown and Poon 2016). Exogenous acetic acid (AA) uses for mitigating abiotic stressors such as drought, salt, and copper stress are substantial (Matsui et al. 2016). Transcriptome profiling in cassava (Manihot esculenta) revealed that AA supplementation improved tolerance of drought by upregulating genes involved in the abscisic acid (ABA) signaling pathway (Utsumi et al. 2019). Sun et al. (2022) proved in apple plants, that the external application of AA influenced the ABA- and jasmonic acid-induced mitogen-activated protein kinase (MAPK) signaling pathways. When compared to only water-sprayed plants, AA-sprayed plants had higher root biomass, which may put up to improved water and nutritional status maintenance, delayed photosynthetic pigment decomposition, and improved photosynthetic rate (Mostofa et al. 2021). Drought-induced effects were mitigated by foliar application of AA, as evidenced by improvements in soybean growth and leaf phenotypes, shoot height, shoot and root DW, total leaf area per trifoliate, and leaf succulence (Rahman et al. 2021); however, the potential different responses of soybean genotypes varying in drought tolerance are lacking. Moreover, the fluorescence traits in response to the sole and the mutual effect of drought and AA application are not fully studied either. In a big field experiment, a total of 25 soybean genotypes were subjected to drought stress during 2017, 2018 and 2019 cropping years (Basal 2021). Based on their performance, 2 genotypes different in their susceptibility to water deprivation; Coraline (drought-susceptible) and Speeda (drought-tolerant) were chosen for this study. Our research focused on evaluating the possible impact of acetic acid in reducing the drought effect on these genotypes by evaluating certain morpho-physiological traits.
Materials and Methods
Experimental Conditions and Treatments
The experiments were conducted at the University of Debrecen, Institute of Crop Sciences at the climatic room of the department of applied plant biology under controlled conditions in 2022. Relative humidity was maintained between 65 and 75%, the light/dark cycle was 16–8 h with a respective 24–20 °C temperature periodicity, and light intensity was kept at a constant 300 µmol m−2s−1 during daytime.
The seeds of the two soybean genotypes, ‘Speeda’ and ‘Coraline,’ were surface sterilized for 20 min with 6% (v/v) H2O2, rinsed well with deionized water, and geotropically germinated within moist filter sheets at 22 °C. Seedlings with good vigor were potted in 1.7 L pots after germination. Three seedlings were placed in each pot. Each pot received 170 ml of a dicot nutritional solution containing 2.0 mM Ca(NO3)2·4H2O; 0.7 mM K2SO4; 0.5 mM MgSO4·7H2O; 0.1 mM KH2PO4; 0.1 mM KCl; 0.5 µM MnSO4·4H2O; 0.5 µM ZnSO4·7H2O; 0.2 µM CuSO4·5H2O and 10 µM H3BO3, iron was provided in the form of 10–4M Fe-EDTA (Cakmak and Marschner 1990). Every 3 days, the nutrient solution in each pot was replaced with a fresh one. Drought was induced using PEG 6000 (VWR International bvba Geldenaaksebaan, Leuven, Belgium) when the plants reached the V3 stage (BBCH 103) (Meier 2018) and kept for 8 days. The PEG concentrations were 0% (D0 = control) and 10% (D1 = drought stress treatment). Along with 10% PEG treatment, 2 ml of 20 mM Acetic Acid (AA) was sprayed on drought-stressed plants each time the nutrient solution was changed, starting from the day PEG was applied until the end of the experiment (8 days after drought stress application) (i.e., at days 1,4 and 7 of PEG imposition). Each treatment had 3 replications. Thus, there were 3 treatments: control treatment (D0), growing in ideal conditions with no drought stress; drought-stressed treatment (D1) and drought-stressed treatment with acetic acid spray applied (D2). The total number of pots was 18 (2 genotypes × 3 treatments × 3 replications).
Determination of Chlorophyll-a, Chlorophyll-b, and Total Carotenoids
The extraction of chlorophyll-a, chlorophyll-b and total carotenoids was done using the procedure outlined by (Moran and Porath 1980). Fifty mg of each fresh leaf was diluted in 5 ml N,N-Dimethylformamide (N,N-DMF). This mixture was then kept in 4 °C for 72 h before the pigment extract concentration was evaluated using UV–Vis spectrophotometry (Metertech SP-830 PLUS, Taiwan) at three wavelengths: 480, 647, and 664 nm. Calculations of chlorophyll-a and chlorophyll-b, as well as total carotenoids, were made using the following equations (Wellburn 1994).
Determination of Chlorophyll Fluorescence Parameters
To quantify chlorophyll fluorescence parameters on dark-adapted leaves, light exclusion clips were placed to the central part of each leaf (avoiding main veins) for 20 min. The characteristics of chlorophyll fluorescence were determined in compliance with Schreiber et al. (1986) using a portable chlorophyll fluorometer-PAM-2100 (WALZ, Germany). The youngest, fully developed leaves were dark-adapted for 20 min. After dark adaptation, the initial fluorescence (Fo) was excited by weak light (0.1 µmol m−2 s−1). The maximal fluorescence (Fm) was induced by white saturating flash (8000 µmol m−2 s−1) (fast phase of chlorophyll fluorescence). The difference between maximum and minimum fluorescence is referred to as variable fluorescence (Fv). The Fv/Fm ratio is an indicator of the maximum quantum yield of photosystem II (a quantitative measure of the maximal photochemical efficiency of photosystem II, called optimal photochemical activity (Kitajima and Butler 1975)).
Additionally, the Fv/Fo value was calculated as an indicator of the size and the number of active photosynthetic reaction centers (Dan et al. 2000). The actual photochemical efficiency of PSII (ΔF/Fm′ = Yield) was determined under growing light intensity.
Determination of Relative Water Content
Five fully matured leaves were collected, and their fresh weight (FW) was determined immediately. The dry weight (DW) of the sample leaves was determined by drying them to a constant mass (after 72 h) at 70 °C. The relative water content (RWC) was determined as follows (Cheng et al. 2012):
Determination of Specific Leaf Area
The specific leaf area (SLA) was calculated by drying five leaf disks from the same fully matured leaves with known area at 70 °C for 48 h, then determining the dry weight and calculating the SLA as stated by Wilson et al. (1999).
Determination of Stomatal Conductance
The AP4 porometer was used to determine the stomatal conductance (gs) (Delta-T devices, UK). It was calculated by taking the average of four values from the youngest fully developed leaves of each repetition.
Determination of Shoot and Root Morphological Traits
On harvest day, one plant was selected from each pot. The roots and shoots were separated. After measuring the length with a standard ruler, they were separately weighed to determine the fresh weight. Following that, they were oven-dried for 72 h at 70 °C and the dry weight was determined.
Determination of Root Volume
Roots of each sample were placed in a graded (ml) tube containing a known volume of water and the rise in water volume upon root insertion, which represents the root volume (cm3) was determined.
Statistical Analyses
The analysis of variance (2-way ANOVA) test was conducted to compare the means of the different treatments (alpha = 0.05). When the difference was significant, the Turkey HSD post hoc test was conducted to indicate the statistically different means (p ≤ 0.05) using GenStat software (Genstat V 26, VSNi, UK).
Results
Morphological Parameters of the Roots
In ‘Speeda,’ the root dry weight was not affected by the imposition of drought stress. However, the plant roots of the drought-stressed treatment that received AA foliar spray had significantly lower dry weight (Fig. 1A). In ‘Coraline,’ on the other hand, the AA foliar application resulted in significantly higher root dry weight as compared to the other treatments.
The root dry weight of AA-sprayed plants (D2) was significantly higher in ‘Coraline’ as compared to ‘Speeda,’ whereas it was significantly lower in both (D0) and (D1) treatments (Fig. 1A).
Both the root length and the root volume of ‘Speeda’ plants decreased significantly as a consequence of drought stress application. Moreover, the AA application did not have a measurable effect on any of these traits. In Corlaine, however, the foliar spray of AA significantly increased both the root length and the root volume of the drought-stressed plants (D2) as compared to the non-treated, drought-stressed counterparts (D1) (Fig. 1B, C).
‘Speeda’ had longer roots, regardless of treatment, and higher root volume in both (D0) and (D1) treatments, whereas the AA-treated (D2) treatment of ‘Coraline’ had significantly higher root volume as compared to (D2) treatment of ‘Speeda’ (Fig. 1B, C).
Morphological Parameters of the Shoots
Drought stress imposition significantly decreased the shoot dry weight of both genotypes. The foliar spray of AA significantly increased the shoot dry weight of ‘Coraline’ plants, but not of ‘Speeda.’ The drought-stressed (D1) ‘Speeda’ plants had significantly higher shoot dry weight as compared to ‘Coraline’ counterparts (Fig. 2A).
In ‘Speeda’, drought stress reduced the shoot length; however, the reduction was insignificant, and the AA foliar spray did not enhance this trait. On the contrary, drought significantly decreased the shoot length of ‘Coraline’ plants, and the AA application could significantly enhance this trait and keep the shoot length on a level very close to that of the control plants. ‘Speeda’ had higher shoot dry weight in both (D0) and (D1) treatments as compared to ‘Coraline,’ and also higher shoot length in all treatments (Fig. 2B).
Specific Leaf Area
Drought stress imposition resulted in decreased specific leaf area (SLA) in both genotypes; however, the decrease was insignificant. The SLA significantly increased in both genotypes in drought-stressed plants sprayed with AA (D2) as compared to (D1) counterparts (Fig. 3).
Regardless of treatment, the differences between the 2 genotypes were slight and insignificant.
Chlorophyll Fluorescence Parameters
The optimal photochemical efficiency of PSII (Fv/Fm) (Fig. 4A), the size, and number of active photosynthetic reaction centers (Fv/Fo) (Fig. 4B) and the actual photochemical efficiency of PSII (Yield) (Fig. 5) decreased in both genotypes when drought stress was imposed, with more announced effect in the case of ‘Coraline.’ These traits were positively influenced by the AA foliar application as their values were restored to levels very close to the control counterparts.
Drought stress resulted in decreased Fv/Fm value in both genotypes similarly; however, ‘Coraline’ plants had significantly higher Fv/Fm values under both control (D0) and AA-treated (D2) treatments (Fig. 4A). Moreover, the actual photochemical efficiency was higher in ‘Coraline,’ regardless of treatment (Fig. 5).
Chlorophyll-a and Chlorophyll-b Contents
Chlorophyll-a level in control treatment (D0) was insignificantly higher as compared to the drought-stressed treatment (D1) in both genotypes. However, the application of AA (D2 treatment) has led to statistically significant increase in chlorophyll-a content as compared to (D1) treatment (Fig. 6A). The differences between the 2 genotypes were insignificant, regardless of treatment.
In both genotypes, drought stress did not result in measurable changes in chlorophyll-b content, however, a significant increase in this trait was recorded in (D2) treatment in both genotypes. The concentration of chlorophyll-b was higher in ‘Coraline’ in (D0), but lower in (D1) and (D2) treatments as compared to ‘Speeda’; however, these differences were insignificant (Fig. 6B).
Total Carotenoids Content
Drought stress resulted in significant reduction in the total carotenoids in both genotypes. However, the drought-stressed plants that were sprayed with AA (D2) had significantly higher total carotenoids content as compared to the drought-stressed treatment (D1). Moreover, (D2) treatment resulted in total carotenoids content that was higher than the control plants in ‘Coraline’ genotype (Fig. 7).
Stomatal Conductance
Significant reduction in the stomatal conductance was recorded in both genotypes as a consequence of subjecting the plants to drought stress. However, the foliar application of AA enhanced this trait in both genotypes, with more announced effect in ‘Speeda’ genotype, where the increase was significant as compared to the drought-stressed counterpart (Fig. 8). Drought stress (D1) reduced the stomatal conductance of both genotypes to similar levels; however, the response of ‘Speeda’ to foliar AA application (D2) was significantly higher than that of ‘Coraline’ (Fig. 8).
Relative Water Content
The relative water content significantly decreased in both genotypes as a result of drought stress imposition, and the AA foliar spray could not alleviate the effect of drought. Both genotypes reacted similarly, and there were no measurable differences between them (Fig. 9).
Discussion
The optimal photochemical efficiency of PSII is an indicative trait that is widely used to assess the physiological response of drought-stressed plants (Song et al. 2022). In our experiment, the optimal photochemical efficiency of PSII (Fv/Fm), the actual photochemical efficiency of PSII (Yield) and the size and number of active photosynthetic reaction centers (Fv/Fo) decreased in both genotypes under drought stress conditions, with more announced effect on the drought-susceptible genotype (Figs. 4A, B and 5). Zlatev and Lidon (2012) reported a decrease in Fv/Fm and concluded that it can be a measure of photosynthetic down-regulation. Zhang et al. (2016) also reported that the optimal photochemical efficiency of PSII (Fv/Fm) decreased in response to drought stress. We found out that the application of AA restored Fv/Fm, yield and Fv/Fo traits to levels very close to the control counterparts. In their experiment, Khan et al. (2023) reported that salicylic acid (SA) significantly increased both Fv/Fm and yield traits of lemongrass. This increase can be explained by the stimulatory effect of growth biostimulators such as SA on RuBisCO and brassinosteroid analogues DI-31 (Pérez-Borroto et al. 2021) on chlorophyllase enzyme activity. Earlier, Lima and Lobato (2017) indicated that growth biostimulators enhanced light absorption and electron flow, leading to higher quantum efficiency of PSII.
Stomatal conductance is used to quantify the amount of CO2 and water vapor exchanged between the ambient and interior leaf (Atteya 2003). To survive a prolonged duration of drought, it is critical for soybean leaves to modify their stomatal conductance in order to avoid excessive water loss (Ku et al. 2013). In the current experiment, drought decreased the stomatal conductance in both genotypes significantly, and the foliar application of AA enhanced this trait in both genotypes, with more announced effect in the drought-tolerant genotype (Fig. 8). According to Chowdhury (2016), drought stress led to a 42% reduction in stomatal conductance in leaves that are drought stressed leaves in comparison to unstressed. Zhang et al. (2016) discovered a 98.8 percent reduction in stomatal conductance under drought; they stated that decrease in stomatal conductance was caused by a decreased ratio of open stomata to stomatal aperture size in crops exposed to drought. According to Razmi et al. (2017), water stress decreased the stomatal conductance of three soybean leaflets as compared to their non-drought-stressed counterparts, and a foliar application of 0.4 mM salicylic acid (SA) significantly reversed drought-induced stomatal closure and improved it. In comparison to the detrimental effect of water scarcity, SA treatments increased stomatal conductivity. Sadeghipour (2012) found that SA treatment resulted in less stomatal conductance loss than control plants for both common bean genotypes under both control and water-stressed situations. The prevention of stomatal conductance reduction with the administration of SA is critical for maintaining photosynthetic activity and minimizing damage (Idrees et al. 2010).
The leaf water capacity and relative water content are valuable indicators of a plant’s physiological water status (Gonzales and Gonzales-Vilar 2001). We observed significant reductions in the relative water content in both genotypes as a result of drought stress imposition, and these reductions were not influenced by AA application (Fig. 9). It was previously reported that under water deficit conditions, drought-stressed plants with AA treatment had decreased transpiration rate, stomatal conductance, and leaf temperature, which was associated with higher RWC (He et al. 2019). However, in that particular experiment, drought stress was imposed during reproductive stages, and that might explain the contradictory conclusion, taking into consideration the previously mentioned conclusion by Maleki et al. (2013) that the stage at which soybean plants suffer from drought can play a key role in the response and the consequences.
In the current experiment, drought stress reduced the specific leaf area (SLA) in both genotypes. The SLA significantly increased in both genotypes in drought-stressed plants sprayed with AA (D2) as compared to (D1) counterparts, where drought stress was imposed without the pre-treatment with AA (Fig. 3). The enhanced leaf area in (D2) treatment might be justified by promoting cell division and cell expansion as suggested by Khandaker et al. (2017) when using gibberellic acid (GA) as an exogenous foliar spray. Basal and Szabó (2020) concluded that drought stress at reproductive stages significantly decreased the leaf area of 2 soybean genotypes.
Chlorophylls are the primary pigmentations involved in absorption of light, transfer, transfiguration, and chlorophyll concentration is a key indicator of photosynthetic activity (Liu et al. 2007). We found out that chlorophyll-b content was not affected measurably by drought stress in either genotype; however, it was significantly increased in the AA-treated (D2) treatment in both genotypes, indicating that AA may play a role in the production and/or slowing the degradation of photosynthetic pigments, resulting in increased photosynthesis capacity during drought, as reported by Rahman et al. (2021). Drought stress reduced light absorption, according to Dong et al. (2015), resulting in changes in leaf area index and also leaf chlorophyll content. According to Zhang et al. (2016), chlorophyll-a was notably decreased in drought-stressed plants compared to control plants. Drought stress resulted in a considerable decrease in chlorophyll-a + chlorophyll-b (from 19.5 to 13.0 mg g−1 DW), signifying a lowered ability for light absorption and conversion (Tang et al. 2017). Drought stressed plants had a substantial reduction in photosynthetic pigment concentration, but drought-stressed plants treated with AA preserved the same level of photosynthetic proportionality and photosynthetic pigments throughout the drought period (Rahman et al. 2021). The potential benefits of AA treatment on reduced photosynthetic pigment deterioration and increased photosynthesis proportionality have been recently demonstrated in mung bean grown under seawater-induced salt stress (Rahman et al. 2019), lentil grown under copper stress (Hossain et al. 2020) and cassava grown under drought stress (Rahman et al. 2019; Utsumi et al. 2019). Also, the results are in compliance with Sun et al. (2022), whose results indicated that apple plants treated with AA were more drought-tolerant than those treated with water.
Carotenoids have a role in scavenging reactive oxygen species (ROS), stabilizing photosynthetic complexes, assisting with energy dissipation, and assisting plants in mitigating the negative impacts of drought stress (Moharekar et al. 2003). In the current experiment, the total carotenoids in both genotypes decreased significantly as a consequence of drought stress imposition (Fig. 7). Razmi et al. (2017) concluded that in comparison to control, treating soybean genotypes with salicylic acid increased the overall amounts of photosynthetic pigments (carotenoids) in leaves. By distributing surplus energy from light surrounding Photosystem II (PS II) mainly via the xanthophylls cycle, carotenoids can protect chlorophylls from damage (Carol and Kuntz 2001). As a result, it provides critical protection for the photosynthetic system, and its content can represent a plant’s capacity for adaptation to its environment (Tang et al. 2017). Zhang et al. (2016) previously found that drought stress reduced carotenoids composition significantly when compared to control, a finding that was eventually revealed by Tang et al. (2017), who found that revealing plants to drought stress resulted in a notable decrease in carotenoid content. In the current experiment, (D2) treatment had significantly higher total carotenoids content as compared to (D1) treatment. Moreover, (D2) treatment resulted in total carotenoids content higher than that of the control plants in ‘Coraline’ genotype (Fig. 7). It was previously reported that low concentrations of exogenously applied growth regulators (e.g., H2O2) can induce the synthesis of certain enzymes and/or proteins related to photosynthesis process (Jiang et al. 2012), resulting in enhanced pigment content (Liu et al. 2010). Similar conclusions were also reported on soybean in the case of exogenous melatonin (Cao et al. 2019) and ethanol (Das et al. 2022). The mechanism by which these agents enhance photosynthetic pigment content (including carotenoids) is reducing the degradation rate of these pigments under drought stress conditions (Rahman et al. 2022).
The level of response of stressed plants to growth regulators applied is also genotype-dependent. For example, Mohamed and Latif (2017) concluded that methyl jasmonate enhanced drought stress tolerance of “Giza 22” soybean genotype more than that of “Giza 35” genotype. Although we did not measure the endogenous hormonal and enzymatic activities, yet our results show genotype-dependent morpho-physiological differences in response to drought stress imposition and AA application, suggesting that a molecular analysis will help further in understanding the response of different soybean genotypes to drought and AA application and, thus, selecting the genotypes that better respond to AA application under drought stress conditions.
In our experiment, the root dry weight of the drought-tolerant genotype was not affected by the imposition of drought stress. However, the plant roots of the drought-stressed treatment that received AA foliar spray had significantly lower dry weight (Fig. 1A). On the other hand, the AA foliar application resulted in significantly higher root dry weight as compared to the other treatments in the case of the drought-susceptible genotype. These different reactions can be a result of the differences between the 2 genotypes in terms of their response drought stress and AA application and might be a key factor when selecting genotypes to be cultivated under unfavorable conditions.
Drought stress significantly decreased both the root length and the root volume of ‘Speeda’ plants, and the AA application did not influence any of these traits remarkably. In ‘Corlaine,’ however, AA application significantly increased both the root length and the root volume of (D2) treatment as compared to (D1) treatment (Fig. 1A, B). In their experiment, Bashir et al. (2019) concluded that the root length of 8 soybean genotypes decreased significantly as a result of the drought stress imposed by a 10% PEG solution. A similar conclusion was also reported later by Sohag et al. (2020). In addition, it was previously reported that the exogenous application of H2O2 on rice plants (Sohag et al. 2020) and ethanol on soybean (Rahman et al. 2021) could partially alleviate the negative effects of drought stress on the root morphology, which is in line with our findings on ‘Coraline’ plants.
Drought stress has been linked to a decrease in soybean biomass (Khan and Komatsu 2016). We found out that shoot dry weight decreased significantly in both genotypes under drought stress conditions, and the shoot dry weight of drought-stressed ‘Coraline’ plants, but not of ‘Speeda,’ was significantly higher in AA-treated treatment (D2) than in (D1) treatment. The drought-stressed (D1) ‘Speeda’ plants had significantly higher shoot dry weight as compared to ‘Coraline’ counterparts (Fig. 2A). We also found out that in ‘Speeda,’ drought stress reduced the shoot length of both genotypes, with more announced effect on ‘Coraline’ genotype, and the AA foliar spray did not enhance this trait in ‘Speeda,’ but could significantly enhance it in ‘Coraline’ and keep the shoot length on a level very close to that of the control plants (Fig. 2B). When drought stress was imposed at R4 stage rather than V4 stage, biomass was drastically reduced (Maleki et al. 2013), indicating that the stage of soybean life cycle at which drought occurs has an effect as well. Previously, Mak et al. (2014) reported that drought stress significantly decreased the shoot length of soybean plants. Garcia et al. (2010) reported the different examined soybean genotypes to be significantly different in plant height compared to one another. Our results support this conclusion as ‘Speeda’ had higher shoot length in all treatments. According to Hossain et al. (2014), drought stress reduced plant height in drought-sensitive and also in drought-tolerant soybean genotypes; nevertheless, the drought-vulnerable genotype had a length rated at 44.3% of the height of control plants, while the two drought-tolerant genotypes had height values of 56.7% and 59.1%, respectively. The authors ascribed this decline to a drought resistance mechanism. Ahmad et al. (2021) reported that drought reduced both shoot length and weight; however, the application of 100 mM salicylic acid increased these parameters significantly. The Authors allocated the decrease in these parameters to increased reactive oxygen species (ROS) accumulation and to changes in the proteins in the cellular walls (Boyer and Westgate 2004).
Conclusions
Drought stress decreased both chlorophyll-a and total carotenoids, the stomatal conductance, and the specific leaf area of both soybean genotypes. However, the foliar application of 20 mM acetic acid enhanced these traits significantly. Drought stress had a negative effect on the optimal and the actual photochemical efficiency of PSII of ‘Coraline,’ but not ‘Speeda,’ and the AA could alleviate that effect. The application of AA could not enhance the relative water content of the drought-stressed plants of both genotypes. The morphology of both the roots and shoots was negatively influenced by the drought application in both genotypes; however, the AA application helped in restoring these traits in ‘Coraline,’ but not ‘Speeda,’ indicating that AA application might be more beneficial in the case of drought-susceptible soybean genotypes.
References
Ahmad A, Aslam Z, Naz M, Hussain S, Javed T, Aslam S, Raza A, Ali HM, Siddiqui MH, Salem MZ, Hano C (2021) Exogenous salicylic acid-induced drought stress tolerance in wheat (Triticum aestivum L.) grown under hydroponic culture. PLoS ONE 16(12):0260556
Atteya AM (2003) Alteration of water relations and yield of corn genotypes in response to drought stress. Bulg J Plant Physiol 29:63–76
Basal O, Szabó A (2020) Ameliorating drought stress effects on soybean physiology and yield by hydrogen peroxide. Agric Conspec Sci 85(3):202
Basal O, Szabó A, Veres S (2020) Physiology of soybean as affected by PEG-induced drought stress. Curr Plant Biol 22:100135
Basal O (2021) The effects of drought stress on soybean physiology, yield and quality. PhD thesis, University of Debrecen http://hdl.handle.net/2437/300871
Bashir W, Anwar S, Zhao Q, Hussain I, Xie F (2019) Interactive effect of drought and cadmium stress on soybean root morphology and gene expression. Ecotoxicol Environ Saf 175:90–101
Boyer JS, Westgate ME (2004) Grain yields with limited water. J Exp Bot 55(407):2385–2394
Brown WH, Poon T (2016) Introduction to organic chemistry. John Wiley & Sons.
Cao L, Jin XJ, Zhang YX (2019) Melatonin confers drought stress tolerance in soybean (Glycine max L.) by modulating photosynthesis, osmolytes, and reactive oxygen metabolism. Photosynthetica 57(3):812–819
Cakmak I, Marschner H (1990) Decrease in nitrate uptake and increase in proton release in zinc deficient cotton, sunflower and buckwheat plants. Plant Soil 129(2):261–268
Carol P, Kuntz M (2001) A plastid terminal oxidase comes to light: implications for carotenoid biosynthesis and chlororespiration. Trends Plant Sci 6(1):31–36. https://doi.org/10.1016/s1360-1385(00)01811-2
Chen J, Wu FH, Wang WH, Zheng CJ, Lin GH, Dong XI et al (2011) Hydrogen sulphide enhances photosynthesis through promoting chloroplast biogenesis, photosynthetic enzyme expression, and thiol redox modification in Spinacia oleracea seedlings. J Exp Bot 62:4481–4493. https://doi.org/10.1093/jxb/err145
Chen J, Shang YT, Wang WH, Chen XY, He EM, Zheng HL (2016) Hydrogen sulfide-mediated polyamines and sugar changes are involved in hydrogen sulfide-induced drought tolerance in Spinacia oleracea seedlings. Front Plant Sci 7:1173
Cheng T, Rivard B, Sánchez-Azofeifa AG, Féret JB, Jacquemoud S, Ustin SL (2012) Predicting leaf gravimetric water content from foliar reflectance across a range of plant species using continuous wavelet analysis. J Plant Physiol 169(12):1134–1142
Chowdhury J, Karim M, Khaliq Q, Ahmed A, Khan M (2016) Effect of drought stress on gas exchange characteristics of four soybean genotypes. Bangladesh J Agric Res 41(2):195–205. https://doi.org/10.3329/bjar.v41i2.28215
Das AK, Anik TR, Rahman MM, Keya SS, Islam MR, Rahman MA, Sultana S, Ghosh PK, Khan S, Ahamed T et al (2022) Ethanol treatment enhances physiological and biochemical responses to mitigate saline toxicity in soybean. Plants 11:272. https://doi.org/10.3390/plants11030272
Dan TV, KrishnaRaj S, Saxena PK (2000) Metal tolerance of scented geranium (Pelargonium sp. “Frensham”): effects of cadmium and nickel on chlorophyll fluorescence kinetics. Int J Phytoremediation 2(1):91–104
Dong J, Xiao X, Wagle P, Zhang G, Zhou Y, Jin C, Torn MS, Meyers TP, Suyker AE, Wang J, Yan H, Biradar CH, Moore IIIB (2015) Comparison of four EVI-based models for estimating gross primary production of maize and soybean croplands and tallgrass prairie under severe drought. Remote Sens Environ 162:154–168. https://doi.org/10.1016/j.rse.2015.02.022
Dos Santos TB, Ribas AF, De Souza SGH, Budzinski IGF, Domingues DS (2022) Physiological responses to drought, salinity, and heat stress in plants: a review. Stresses 2:113–135. https://doi.org/10.3390/stresses2010009
Garcia AG, Persson T, Guerra LC, Hoogenboom G (2010) Response of soybean genotypes to different irrigation regimes in a humid region of the southeastern USA. Agric Water Manag 97:981–987
Gáspár S, Basal O, Simkó A, Kiss L, Frommer D, Veres S (2022) Production of hull-less mutant of pumpkin seed under different abiotic conditions. Tekirdağ Ziraat Fakültesi Dergisi 19(3):508–514
Godfray HCJ, Beddington JR, Crute IR, Haddad L, Lawrence D, Muir JF, Pretty J, Robinson S, Thomas SM, Toulmin C (2010) Food security: the challenge of feeding 9 billion people. Science 327(5967):812–818. https://doi.org/10.1126/science.1185383
Gonzales L, Gonzales-Vilar M (2001) Determination of relative water content. Handbook of Plant Ecophysiology Techniques. Kluwer Academic Publishers, Dordrecht, pp 207–212
He J, Jin Y, Turner NC, Chen Z, Liu HY, Wang XL, Siddique KH, Li FM (2019) Phosphorus application increases root growth, improves daily water use during the reproductive stage, and increases grain yield in soybean subjected to water shortage. Environ Exp Bot 166:103816. https://doi.org/10.1016/j.envexpbot.2019.103816
Hossain MM, Liu X, Qi X, Lam HM, Zhang J (2014) Differences between soybean genotypes in physiological response to sequential soil drying and rewetting. Crop J 2(6):366–380. https://doi.org/10.1016/j.cj.2014.08.001
Hossain MS, Abdelrahman M, Tran CD, Nguyen KH, Chu HD, Watanabe Y, Hasanuzzaman M, Mohsin SM, Fujita M, Tran LSP (2020) Insights into acetate-mediated copper homeostasis and antioxidant defense in lentil under excessive copper stress. Environ Pollut 258:113544. https://doi.org/10.1016/j.envpol.2019.113544
Hu J, Li Y, Liu Y, Kang D, Wei H, Jeong BR (2020) Hydrogen sulfide affects the root development of strawberry during plug transplant production. Agriculture 10(1):12. https://doi.org/10.3390/agriculture10010012
Huang XY, Chao DY, Gao JP, Zhu MZ, Shi M, Lin HX (2009) A previously unknown zinc finger protein, DST, regulates drought and salt tolerance in rice via stomatal aperture control. Genes Dev 23(15):1805–1817. https://doi.org/10.1101/gad.1812409
Hussain HA, Hussain S, Khaliq A, Ashraf U, Anjum SA, Men S, Wang L (2018) Chilling and drought stresses in crop plants: implications, cross talk, and potential management opportunities. Front Plant Sci 9:393. https://doi.org/10.3389/fpls.2018.00393
Idrees M, Khan MMA, Aftab T, Naeem M, Hashmi N (2010) Salicylic acid induced physiological and biochemical changes in lemongrass varieties under water stress. J Plant Interact 5(4):293–303
Jiang YP, Cheng F, Zhou YH, Xia XJ, Mao WH, Shi K, Chen ZX, Yu JQ (2012) Hydrogen peroxide functions as a secondary messenger for brassinosteroids-induced CO2 assimilation and carbohydrate metabolism in Cucumis sativus. J Zhejiang Univ Sci B 13(10):811–823
Kato-Noguchi H, Kugimiya T (2001) Effects of ethanol on growth of rice seedlings. Plant Growth Regul 35:93–96. https://doi.org/10.1023/A:1013850707053
Khan MN, Komatsu S (2016) Proteomic analysis of soybean root including hypocotyl during recovery from drought stress. J Proteom 144:39–50. https://doi.org/10.1016/j.jprot.2016.06.006
Khan MM, Afreen R, Quasar N, Khanam N, Uddin M (2023) Steam-mediated foliar application of catechol and plant growth regulators enhances the growth attributes, photosynthesis, and essential oil production of lemongrass [Cymbopogon flexuosus (Steud.) Wats]. Biocatal Agric Biotechnol 48:102638
Khandaker MM, Awang IZ, Ismail SZ (2017) Effects of naphthalene acetic acid and gibberellic acid on plant physiological characteristics of wax apple (var. Jambu madu). Bulgarian J Agric Sci 23(3):396–404
Khatun M, Sarkar S, Era FM, Islam AKMM, Anwar MP, Fahad S, Datta R, Islam AKMA (2021) Drought stress in grain legumes: effects. Toler Mech Manag Agron 11:2374
Kitajima M, Butler WL (1975) Quenching of chlorophyll fluorescence and primary photochemistry in chloroplast dibromothymoquinone. Biochim Biophys Acta 376:105–115
Ku YS, Au-Yeung WK, Yung YL, Li MW, Wen CQ, Liu X, Lam HM (2013) Drought stress and tolerance in soybean. Compr Surv Int Soybean Res Genet Physiol Agron Nitrogen Relationsh. https://doi.org/10.5772/52945
Li J, Shi C, Wang X, Liu C, Ding X, Ma P et al (2020) Hydrogen sulfide regulates the activity of antioxidant enzymes through per sulfidation and improves the resistance of tomato seedling to copper oxide nanoparticles (CuO NPs)-induced oxidative stress. Plant Physiol Biochem 156:257–266. https://doi.org/10.1016/j.plaphy.2020.09.020
Lima JV, Lobato AK (2017) Brassinosteroids improve photosystem II efficiency, gas exchange, antioxidant enzymes and growth of cowpea plants exposed to water deficit. Physiol Mol Biol Plants 23:59–72
Lisjak M, Teklic T, Wilson ID, Wood M, Whiteman M, Hancock JT (2011) Hydrogen sulfide effects on stomatal apertures. Plant Signal Behav 6:1444–1446. https://doi.org/10.4161/psb.6.10.17104
Liu ZH, Shi LR, Bai LR, Zhao KF (2007) Effects of salt stress on the contents of chlorophyll and organic solutes in Aeluropus littoralis var. sinensis Debeaux. Journal of Plant Physiology and Molecular Biology 33(2):165–172
Liu ZJ, Guo YK, Bai JG (2010) Exogenous hydrogen peroxide changes antioxidant enzyme activity and protects ultrastructure in leaves of two cucumber ecotypes under osmotic stress. J Plant Growth Regul 29:171–183
Mak M, Babla M, Xu SC, O’Carrigan A, Liu XH, Gong YM, Holford P, Chen ZH (2014) Leaf mesophyll K+, H+ and Ca2+ fluxes are involved in drought-induced decrease in photosynthesis and stomatal closure in soybean. Environ Exp Bot 98:1–12
Maleki A, Naderi A, Naseri R, Fathi A, Bahamin S, Maleki R (2013) Physiological performance of soybean genotypes under drought stress. Bull Env Pharmacol Life Sci 2(6):38–44
Matsui N, Nakata K, Cornelius C, Macdonald M (2016) Diagnosing maize growth for determination of optimum fertilizer application time in northern Malawi. J Agric Sci 8(5):50–60. https://doi.org/10.5539/jas.v8n5p50
Meier U (2018) Growth stages of mono- and dicotyledonous plants. BBCH Monogr Quedlinburg Open Agrar Repos. https://doi.org/10.5073/20180906-074619
Mohamed HI, Latif HH (2017) Improvement of drought tolerance of soybean plants by using methyl jasmonate. Physiol Mol Biol Plants 23:545–556
Moharekar ST, Moharekar SD, Hara T, Tanaka R, Tanaka A, Chavan PD (2003) Effect of salicylic acid on chlorophyll and carotenoid contents of wheat and moong seedlings. Photosynthetica 41:315–317. https://doi.org/10.1023/B:PHOT.0000011970.62172.15
Moran R, Porath D (1980) Chlorophyll determination in intact tissues using N, N-Dimethylformamide. Plant Physiol 65(3):478–479. https://doi.org/10.1104/pp.65.3.478
Mostofa MG, Rahman MM, Ansary MMU, Keya SS, Abdelrahman M, Miah MG, Phan-Tran LS (2021) Silicon in mitigation of abiotic stress-induced oxidative damage in plants. Crit Rev Biotechnol 41(6):918–934. https://doi.org/10.1080/07388551.2021.1892582
Müller M, Schneider JR, Klein VA, Da-Silva E, Da-Silva JP Jr, Souza AM, Chavarria G (2021) Soybean root growth in response to chemical. Phys Biol Soil Variat 12:272. https://doi.org/10.3389/fpls.2021.602569
Nabi RBS, Tayade R, Hussain A, Adhikari A, Lee IJ, Loake GJ, Yun BW (2021) A novel DUF569 gene is a positive regulator of the drought stress response in arabidopsis. Int J Mol Sci 22(10):5316
Nadeem M, Li J, Yahya M, Sher A, Ma C, Wang X, Qiu L (2019) Research progress and perspective on drought stress in legumes: a review. Int J Mol Sci 20:2541. https://doi.org/10.3390/ijms20102541
Nguyen HM, Sako K, Matsui A, Suzuki Y, Mostofa MG, Ha CV, Tanaka M, Tran LSP, Habu Y, Seki M (2017) Ethanol enhances high-salinity stress tolerance by detoxifying reactive oxygen species in Arabidopsis thaliana and rice. Front Plant Sci 8:1001. https://doi.org/10.3389/fpls.2017.01001
Pérez-Borroto LS, Toum L, Castagnaro AP, González-Olmedo JL, Coll-Manchado F, Pardo EM, Coll-García Y (2021) Brassinosteroid and brassinosteroid-mimic differentially modulate Arabidopsis thaliana fitness under drought. Plant Growth Regul 95(1):33–47
Rahman MM, Mostofa MG, Rahman MA, Islam MR, Keya SS, Das AK, Miah MG, Kawser AR, Ahsan SM, Hashem A, Tabassum B (2019) Acetic acid: a cost-effective agent for mitigation of seawater-induced salt toxicity in mung bean. Sci Rep 9:1–15. https://doi.org/10.1038/s41598-019-51178-w
Rahman M, Mostofa MG, Keya SS, Rahman A, Das AK, Islam R, Abdelrahman M, Bhuiyan SU, Naznin T, Ansary MU, Tran LS (2021) Acetic acid improves drought acclimation in soybean: an integrative response of photosynthesis, osmoregulation, mineral uptake and antioxidant defense. Physiol Plant 172(2):334–350. https://doi.org/10.1111/ppl.13191
Rahman MM, Mostofa MG, Das AK, Anik TR, Keya SS, Ahsan SM, Khan MA, Ahmed M, Rahman MA, Hossain MM, Tran LS (2022) Ethanol positively modulates photosynthetic traits, antioxidant defense and osmoprotectant levels to enhance drought acclimatization in soybean. Antioxidants 11(3):516
Razmi N, Ebadi A, Daneshian J, Jahanbakhsh S (2017) Salicylic acid induced changes on antioxidant capacity, pigments and grain yield of soybean genotypes in water deficit condition. J Plant Interact 12(1):457–464. https://doi.org/10.1080/17429145.2017.1392623
Sadeghipour O (2012) The role of exogenous salicylic acid (SA) on phytohormonal changes and drought tolerance in common bean (Phaseolus vulgaris L.). J Biodivers Environ Sci 2:8–15
Schreiber U, Schliwa U, Bilger W (1986) Continuous recording of photochemical and non-photochemical chlorophyll fluorescence quenching with a new type of modulation fluorometer. Photosynth Res 10(1–2):51–62
Shi H, Ye T, Han N, Bian H, Liu X, Chan Z (2015) Hydrogen sulfide regulates abiotic stress tolerance and biotic stress resistance in Arabidopsis. J Integr Plant Biol 57(7):628–640. https://doi.org/10.1111/jipb.12302
Sohag AAM, Tahjib-Ul-Arif M, Brestič M, Afrin S, Sakil MA, Hossain MT, Hossain MA, Hossain MA (2020) Exogenous salicylic acid and hydrogen peroxide attenuates drought stress in rice. Plant Soil Environ 66:7–13
Song S, Li X, Wang X, Zhou Q, Li Y, Wang X, Dong S (2022) Effects of drought stress on key enzymes of carbon metabolism, photosynthetic characteristics and agronomic traits of soybean at the flowering stage under different soil substrates. Phyton-Int J Exp Bot 91(11):2475–2490
Sun T, Zhang J, Zhang Q, Li X, Li M, Yang Y, Zhou J, Wei Q, Zhou B (2022) Exogenous application of acetic acid enhances drought tolerance by influencing the MAPK signaling pathway induced by ABA and JA in apple plants. Tree Physiol. https://doi.org/10.1093/treephys/tpac034
Swigonska S, Weidner S (2013) Proteomic analysis of response to long-term continuous stress in roots of germinating soybean seeds. J Plant Physiol 170(5):470–479. https://doi.org/10.1016/j.jplph.2012.11.020
Tang Y, Sun X, Wen T, Liu M, Yang M, Chen X (2017) Implications of terminal oxidase function in regulation of salicylic acid on soybean seedling photosynthetic performance under water stress. Plant Physiol Biochem 112:19–28. https://doi.org/10.1016/j.plaphy.2016.11.016
Tilman D, Balzer C, Hill J, Befort BL (2011) Global food demand and the sustainable intensification of agriculture. Proc Natl Acad Sci USA 108(50):20260–20264
Utsumi Y, Ha CV, Utsumi C, Tanaka M, Takahashi S, Matsui A, Matsunaga TM, Matsunaga S, Okamoto Y, Moriya E, Seki M (2019) Acetic acid treatment enhances drought avoidance in cassava (Manihot esculenta Crantz). Front Plant Sci 10:521. https://doi.org/10.3389/fpls.2019.00521
Wei Y, Jin J, Jiang S, Ning S, Liu L (2018) Quantitative response of soybean development and yield to drought stress during different growth stages in the Huaibei Plain. China Agron 8(7):97. https://doi.org/10.3390/agronomy8070097
Wellburn AR (1994) The spectral determination of chlorophylls a and b, as well as total carotenoids, using various solvents with spectrophotometers of different resolution. J Plant Physiol 144:307–313
Wilson J, Thompson K, Hodgson JG (1999) Specific leaf area and leaf dry matter content as alternative predictors of plant strategies. New Phytol 143:155–162
Zhang J, Liu J, Yang C, Du S, Yang W (2016) Photosynthetic performance of soybean plants to water deficit under high and low light intensity. S Afr J Bot 105:279–287. https://doi.org/10.1016/j.sajb.2016.04.011
Zia R, Nawaz MS, Siddique MJ, Hakim S, Imran A (2021) Plant survival under drought stress: implications, adaptive responses, and integrated rhizosphere management strategy for stress mitigation. Microbiol Res 242:126626. https://doi.org/10.1016/j.micres.2020.126626
Zlatev Z, Lidon FC (2012) An overview on drought induced changes in plant growth, water relations and photosynthesis. Emir J Food Agric 57–72
Acknowledgements
Project no. TKP2021-NKTA-32 has been implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the TKP2021-NKTA funding scheme. This study was also supported by the National Research, Development and Innovation Office of Hungary under Grant: RRF-2.3.1-21-2022-00008.
Funding
Open access funding provided by University of Debrecen. The authors declare that no funds, grants, or other support was received during the preparation of this manuscript.
Author information
Authors and Affiliations
Contributions
OB contributed to methodology, statistical analyses, and revising the manuscript. UM contributed to measurements and writing the manuscript draft. SV contributed to methodology and revising the manuscript.
Corresponding author
Ethics declarations
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Additional information
Handling Editor: Charitha Jayasinghege.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Basal, O., Munkhbat, U. & Veres, S. Enhancing Drought Tolerance in Two Soybean Genotypes with Varied Susceptibilities Through Foliar Application of Acetic Acid. J Plant Growth Regul 43, 1304–1315 (2024). https://doi.org/10.1007/s00344-023-11184-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00344-023-11184-9