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Article

Potassium Nutrition Induced Salinity Mitigation in Mungbean [Vigna radiata (L.) Wilczek] by Altering Biomass and Physio-Biochemical Processes

by
Muhammad Yousaf Shani
1,2,
M. Yasin Ashraf
1,3,*,
Ammara Khalid Butt
3,
Shahid Abbas
4,
Muhammad Nasif
5,
Zafran Khan
6,
Rosario Paolo Mauro
7,*,
Claudio Cannata
7,
Nimra Gul
6,
Maria Ghaffar
1,2 and
Faiqa Amin
8
1
Nuclear Institute for Agriculture and Biology College (NIAB-C), Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad 45650, Pakistan
2
Plant Breeding and Genetics Division, Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad 38000, Pakistan
3
Institute of Molecular Biology and Biotechnology, The University of Lahore, Lahore 54590, Pakistan
4
Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38000, Pakistan
5
Department of Applied Chemistry, Government College University, Faisalabad 38000, Pakistan
6
Department of Plant Breeding and Genetics, University of Agriculture Faisalabad, Faisalabad 38000, Pakistan
7
Dipartimento di Agricoltura, Alimentazione e Ambiente (Di3A), University of Catania, Via S. Sofia 100, 95123 Catania, Italy
8
Department of Botany, Government College of Science, College Road, Faisalabad 38000, Pakistan
*
Authors to whom correspondence should be addressed.
Horticulturae 2024, 10(6), 549; https://doi.org/10.3390/horticulturae10060549
Submission received: 20 April 2024 / Revised: 21 May 2024 / Accepted: 21 May 2024 / Published: 24 May 2024
(This article belongs to the Special Issue Plants Response to Abiotic Stresses: Strategies for Adaptations and Survival)
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Abstract

:
The present investigation was conducted to explore the role of potassium nutrition in improving biomass and physio-chemical alterations to reduce the adverse effects of salinity in mungbean. A sand-culture experiment was carried out under different salinity levels (0, 50, and 100 mM NaCl) with two levels of potassium (0 and 50 mM K2SO4) and two mungbean cultivars (NM-92 and Ramzan), and the alterations in mungbean biomass and metabolic activities were investigated. The results suggested that salinity significantly reduced the biomass, nitrate reductase activity (NRA), nitrite reductase activity (NiRA), total soluble proteins, chlorophyll a, chlorophyll b, total chlorophyll, nitrogen, potassium, calcium, magnesium, and phosphorous contents in both mungbean cultivars in comparison to the control. However, K2SO4 at 50 mM significantly improved all the parameters in both mungbean cultivars except for the sodium content. A significant increase in the total free amino acids, carotenoids, and sodium content in both mungbean cultivars was observed due to salt stress. Moreover, principal component analysis and heatmaps were developed individually for both mungbean cultivars to assess the variability and correlation among the studied attributes under all applied treatments. Under saline conditions, the mungbean ‘Ramzan’ showed more marked reductions in almost all the growth parameters as compared to ‘NM-92’. The results suggest that the application of K2SO4 ameliorates the adverse effects of salinity by regulating osmolyte production, NRA, and NiRA, thus promoting plant growth and productivity.

1. Introduction

Soil salinity is among the main causes of soil degradation after soil erosion and poses a major challenge to agricultural productivity across the globe. Currently, salinity stress affects 7% of the world’s land area, totaling one billion hectares worldwide [1]. According to the Food and Agriculture Organization (FAO) 2015 report, approximately 412 million hectares and 618 million hectares of land were reported to be affected by salinity and sodicity, respectively [2]. Salinity leads to the death of crop plants by prevailing metabolic damage and growth retardation, resulting in crop mortality [3]. The induction of salinity stress in arable land is anticipated to intensify due to the rising temperatures and altered precipitation patterns resulting from climate change, mostly in arid and semi-arid regions across the globe [4]. To escalate crop yield attributes and mitigate salinity stress, the establishment of climate-smart agricultural practices is needed. These measures will assist in ensuring food security for a rapidly growing population.
Mungbean belongs to the Fabaceae family, which has over 150 varieties, originating primarily from Asia and Africa [5]. In Pakistan, mungbean is well known as a summer pulse cash. The exploitation of modern breeding approaches aids in developing climate-smart mungbean cultivars for supporting the economies of developing countries like Pakistan. The deployment of modern breeding strategies assists in developing biotic- and abiotic-resilient mungbean varieties. It is grown mainly in the spring and winter seasons and is considered a chief source of carbohydrates (60.4%), proteins (28.3%), and lipids (1.3%) [6]. It is a short season, self-pollinated, eco-friendly leguminous crop. Mungbean is a good returning crop for farmers in Pakistan and is therefore cultivated in a 257.7-thousand-hectare area, with an average yield of 537 kg ha−1 [7].
Potassium is indispensable for several plant processes, like the regulation of the Na+/K+ pump, and leads to membrane integrity, playing a crucial role in maintaining cell homeostasis. It is a prerequisite element for triggering the activation of about 60 enzymes that are involved in plant growth processes. High levels of potassium also contribute to enhancing the physical quality and disease resilience of plants as well as improving the shelf-life of vegetables and fruits [8]. Without a proper supply of potassium, plants are incapable of synthesizing proteins despite the availability of nitrogen being in abundance [9]. The main cause of potassium deficiency in plants is the antagonistic relationship between sodium and potassium uptake. Sodium and potassium compete at the ion uptake site in the plasmalemma. Exogenous application of K2CO3 to the halophyte Sophora alopecuroides improves the chlorophyll content, gas exchange parameters, and K+/Na+ ratio [10].
Crop plants are exposed to combined stresses; their responses to combinatorial stress individually differ from abiotic stresses and affect the plants’ metabolism, growth, and yield [11]. Thus, the effect of both salinity and a K deficiency is a potential threat to crop survival and productivity. Therefore, it is vital to understand any strategy for protecting the crops. Plants tend to show various mechanisms to alleviate the stress responses; therefore, different agricultural practices have been used by farmers for the reclamation of salinity stress or K deficiency in the field. However, these approaches are not very efficient or are unable to be adopted by farmers under various environmental circumstances [12,13]. Although many studies have been conducted on the individual stresses that plants are subjected to, the effect of combined stresses, such as salt stress and limited K, on major crops still needs to be elucidated. The present study aims to show how the application of potassium ameliorates salt stress in mungbean plants by increasing osmolytes and chlorophyll contents and by regulating enzymes, especially the key enzymes of nitrogen metabolism, nitrate, and nitrite reductases, as well as the Na+ and K+ contents, and other major macronutrients.
Plants need the supply of critical minerals for optimal plant growth and development. There are several approaches to increasing salinity tolerance in plants, including the cultivation of salt-tolerant plants, chemical procedures, and nutrient management in salt-affected soils [14]. On the other hand, the use of potassium is well below the required limits. Because Na+ and K+ have physiological similarities, K+ acquisition is an issue [15]. Under saline conditions, potassium contributes more to osmotic adjustment than Na+, Cl−, or glycine betaine, and it promotes key enzyme activities such as pyruvate production. It also contributes significantly to the vacuole’s osmotic pressure, ensuring cell turgor [16]. Keeping in view the prevalence of salinity in Pakistani soils, improvement in salt tolerance and crop yields due to potassium management in saline soils, thus good economic returns and a short duration of mungbean crop, the present investigation was conducted to test the hypothesis that “proper supply of potassium may promote plant growth and productivity by adapting physio-biochemical alterations in mungbean plants under normal and saline conditions”.

2. Materials and Methods

The seeds of two mungbean cultivars, “NM-92” (a high-yielding and disease-resistant variety, approved in 1996 for general cultivation in Pakistan due to its high seed production, and is very popular among farmers, who are still cultivating them) and “Ramzan” (this mungbean was approved in 2008, takes 10 days to mature early, and is a bold seed compared to that of NM-92 but gives high yields in KPK and agro-climatic conditions) were used in this investigation. The seeds of these mungbean varieties were obtained from the “Plant Breeding and Genetics, Division, Nuclear Institute for Agriculture and Biology, Faisalabad, Pakistan”. The experiment was conducted during March–April 2022 in the NIAB greenhouse (control temperature and lightroom), where day/night temperatures were 25/30 °C, and the light intensity was 1000 µmol m−2 S−1 with a photoperiod of 12 h. The mungbean varieties were maintained in plastic containers (0.3 m diameter × 0.2 m depth) filled with washed river sand (inert growth media, which does not interfere with the salinity or nutrients), and three levels of salinity (0, 50, and 100 mM) were created with sodium chloride (AnalaR-grade NaCl, Merck) and two potassium sulfate (K2SO4) levels (0 and 50 mM), applied through irrigation (Table 1a). We selected the salinity levels and potassium because mungbean is a salt-sensitive crop; a 10% decrease in growth and yield was reported by an increase in every 1 dS m−1 (10 mM NaCl) over 4 dS m−1 salinity. Furthermore, a literature survey also confirmed that 100 mM NaCl or a 10 dSm−1 salinity level causes maximum damage to crops’ growth and productivity. Therefore, this investigation was performed at 0, 50, and 100 mM NaCl levels. We have also performed many experiments on wheat, rice, Kinnow, and sunflower by creating different levels of potassium with K2SO4, and our published results suggested that the 50 mM level was the most appropriate to combat salinity. This is why we selected this level of potassium.
The experiment was arranged in a completely randomized design (CRD), and each treatment was replicated thrice. The seeds of mungbean varieties were surfaces sterilized with sodium hypochlorite (5%), and 10 seeds of each variety were sown at 1 cm depth in each plastic container; after the completion of germination, five seedlings were maintained in each pot. The pots were irrigated with Hoagland’s 1/10th strength solution (Table 1b). When the seedlings were a week old, salinity was imposed as per the saturation percentage of the sand (20%). To avoid the sudden shock of salinity, two levels of 50 mM salinity levels were delivered after 3 days of the first application to achieve the 100 mM concentration. After creating varying salinity levels, the plants were allowed to develop for one week. Then, in both saline and control conditions, 50 mM potassium was added to the growth media, while in the control plants, only distilled water was supplied. Plants were harvested seven days after potassium supplementation, and the physio-biochemical alterations were measured.

2.1. Growth Parameters

A measuring scale (meter rod graduated up to mm) was used to determine the length of the roots and shoots. The number of leaves was determined. The fresh and dry biomass of plants was measured using a digital (0.001) electrical balance (Sartorius, Beijing, China).

2.2. Biochemical Analyses

All the biochemical analytic work was conducted at the Plant Stress Physiology Lab., NIAB, Faisalabad, Pakistan.

2.2.1. Nitrate Reductase Activity

The nitrate reductase activity (NRA) in mungbean leaves was determined according to the method of [17]. Potassium nitrate (KNO3) was used as a substrate, and its 0.02 M was prepared in 0.2 M phosphate buffer, which had a pH of 7.0. Fresh plant (leaves) material (1 g) was homogenized in 10 mL of phosphate buffer (pH 7.0) containing 0.02 M KNO3. The samples were incubated in the dark at 32 °C for 1 h. After incubation, 1 mL of the reaction medium was taken in another test tube (tube-II) and mixed with 0.5 mL of the sulfanilamide prepared in 2 N HCl to stop the enzymatic reaction. After this, 0.5 mL of 1-Naphthylethylene diamine dihydrogen chloride was added. A pink diazo color complex was produced due to the NO2 formation. The absorbance was read at 542 nm against a set of standards developed with NaNO2 on a spectrophotometer (Hitachi-200, Hitachi, Tochigi, Japan).

2.2.2. Nitrite Reductase Activity

The nitrite reductase activity (NiRA) in mungbean leaves was determined following the method of [18]. Sodium nitrite (NaNO2) was used as a substrate. Sodium nitrite solution (0.02 M) in a phosphate buffer with a pH of 5.0 was prepared. Fresh plant material (0.5 g) was homogenized in 4.5 mL of phosphate buffer (pH 7.0) and 0.5 mL of NaNO2 (0.02 M). The samples were incubated at 30 °C in a water bath with gentle shaking for 30 min. The samples were then transferred to boiling water for two minutes to terminate the reaction, and then the reaction mixture was cooled. One mL of cooled extract was taken and treated with 1% sulfanilamide prepared in 2 N HCl and 0.02% of aqueous solution of N 1-Naphthyl-ethylene diamine dihydrochloride; color was developed, and then the optical density was read at 542 nm on a spectrophotometer (Hitachi-220). A standard curve with NaNO2 was developed. The activity of NiRA was determined as NO2 utilized g−1 fresh Weight h−1.

2.2.3. Total Free Amino Acids

For the estimation of total free amino acids (TFAA), 1 mL from each sample (extracted in 0.2 M phosphate buffer, pH 7.0) was taken in test tubes, and 1 mL of 10% pyridine and 1 mL of 2% ninhydrin solution was added into each tube. The tubes were then heated in a boiling water bath for about 30 min. The contents of each tube were then made to 50 mL with distilled water. The optical densities of these colored solutions were then read at 570 nm using a spectrophotometer (Hitachi-200), and the free amino acids were calculated according to [19] using a standard curve established through different concentrations of Alanine.

2.2.4. Total Soluble Proteins

Total soluble proteins were determined using the method of [20]. Fresh plant material of 1.0 g was extracted with 10 mL of 0.2 M phosphate buffer with a pH of 7. A sample of 1 mL was taken in 20 mL capacity test tubes, and 1 mL of solution 50 of solution (2 g of Na2CO3, 0.2 g of NaOH, and 1 g of Na-K tartrate were dissolved in distilled water and the volume was made up to 100 mL) and 1.0 mL of another solution (0.5 g of CuSO4.5H2O dissolved in distilled water and the volume was made up to 100 mL) to prepare the alkaline copper solution. This solution is always prepared fresh] was added to each tube. The tubes were thoroughly mixed and allowed to stand for 30 min at room temperature. Then, 0.1 mL of 1:1 diluted Folin–Ciocalteu reagent was added, mixed well, and kept for 30 min at room temperature. The optical density (O.D) was measured at 620 nm on a spectrophotometer (Hitachi-200). Total soluble proteins were estimated using a standard curve established through different concentrations of BSA.

2.2.5. Chlorophyll and Carotenoids Content

Chlorophylls and carotenoid contents from mungbean leaf samples were extracted by grinding them in 80% acetone, according to [21]. The samples were centrifuged at 14,000× g for 5 min, and the supernatant absorbance (optical density; OD) was measured at 645, 663, and 480 nm on a spectrophotometer (Hitachi, U-2800). The formulae of [22] were used to determine the chlorophyll and carotenoid contents. The concentrations of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were calculated by using the following formulas.
Chlorophyll a = [12.7 (OD 663) − 2.69 (OD 645)] × V/1000 × W
Chlorophyll b = [22.9 (OD 645) − 4.68 (OD 663)] × V/1000 × W
Total chlorophyll = Chla + Chlb = [20.2 (OD 645) − 8.02 (OD 663)] × V/1000 × W
Carotenoids = Acar/Em × 100
where
Acar = [OD 480 + 0.114 (OD 663) − 0.638 (OD 645)] × V/(1000 × W)
W = weight of sample
Em × 100 = 2500
V = volume of extract
FW = Fresh weight of the sample

2.3. Mineral Analyses

To determine the mineral contents in mungbean leaves, the samples were dried in the oven at 70 °C for 2 days. A total of 1 g of dried ground plant material was digested through the H2SO4 and H2O2 method given by [23]. The digested volume of the aliquot was made with +distilled water up to 100 mL in a volumetric flask. A filtered aliquot was used to determine Na, K, Ca, Mg, P, and N. The sodium and potassium contents were determined using a Flame-Photometer (Jenway PFP-7). Calcium and magnesium were determined using the titrimetric method as described by [24]. Nitrogen was estimated by the micro Kjeldahl method [25]. Phosphorus (P) was determined by a spectrophotometer, according to Chang and Jackson [26].

2.4. Statistical Analyses

The data were statistically analyzed using the Statistix 8.1 software application. The significance of the means was checked at the 5% probability level using Tukey’s test, and the means and standard errors were calculated using Microsoft Excel—the 2019 version. Moreover, to assess the variations in the studied attributes under particular treatments, principal component analysis (PCA) and a heatmap were developed using R Software (version 4.3.2).

3. Results

3.1. Growth Parameters

The impact of the salinity and potassium treatments on shoot and root lengths was statistically significant (p ≤ 0.05). In the saline conditions, the potassium treatment notably enhanced the shoot length in both mungbean cultivars (Table 2a). Specifically, under the 50 mM NaCl + K and 100 mM NaCl + K conditions, the shoot lengths were considerably longer than those under 50 mM NaCl (S50) and 100 mM NaCl (S100), respectively (Figure 1A). Similarly, potassium nutrition under saline conditions led to a significant (p ≤ 0.05) increase in root length for mungbean cultivars (Figure 1B). The root lengths were markedly longer in the C + K, > S50 + K, > and S100 + K treatments compared to plants under the control (C), > S50, > and S100, respectively. The influence of salinity and potassium nutrition on the fresh biomass was significant (Table 2a). Plants treated with C + K exhibited the highest fresh biomass, closely followed by the control (C). Conversely, plants grown under S100 displayed the lowest fresh weights (Figure 1C). Likewise, the dry biomass of mungbean cultivars was significantly (p ≤ 0.05) affected by salinity stress and potassium nutrition (Table 2a). A noticeable decrease in dry biomass was observed in the plants subjected to S100 and S50 compared to the control. However, potassium nutrition significantly (p ≤ 0.05) improved the dry biomass, with the highest values recorded in the plants treated with C + K, followed by C > S50 + K > S100 + K > S50 and NaCl S100. Both mungbean cultivars displayed a similar response to salinity stress and potassium nutrition (Figure 1D). The number of leaves was negatively impacted by salinity, and potassium nutrition significantly (p ≤ 0.05) improved this parameter (Table 2a). In contrast to Ramzan, the addition of potassium to the NM-92 plants exposed to S50 resulted in a considerable increase in the number of leaves (Figure 1E).

3.2. Biochemical Parameters

Salinity and potassium nutrition had a significant impact (p ≤ 0.05) on the biochemical attributes, as indicated in (Table 2a,b). Similarly, both salinity stress and potassium nutrition exerted a notable influence on total soluble proteins. Under the control (C) conditions, plants supplemented with potassium exhibited the highest total soluble proteins, although this concentration decreased with salinity. Nevertheless, potassium nutrition proved effective in enhancing the concentration of total soluble proteins even under saline conditions (Figure 2A). Moreover, regarding the nitrate reductase activity (NRA), when comparing C + K, S50 + K, and S100 + K to C, S50, and S100, respectively, a noticeable increase in nitrate reductase activity (NRA) was found in the plants that were supplemented with potassium nutrition (Figure 2B). Furthermore, in terms of the nitrate reductase activity (NRA), a noticeable increase was observed in the plants supplemented with potassium nutrition when comparing C + K, S50 + K, and S100+ K to C, S50, and S100, respectively (Figure 2B). Similarly, under the S50 and S100 treatments, both mungbean cultivars exhibited a significant reduction (p ≤ 0.05) in nitrite reductase activity (NiRA) compared to the control. However, the provision of potassium nutrition to the plants of both mungbean cultivars effectively improved both NRA and NiRA (Figure 2B,C). The ascending trend in NiRA was observed as C + K > S50 + K > and S100 + K (Figure 2C). Additionally, salinity stress and potassium nutrition markedly influenced (p ≤ 0.05) the accumulation of total free amino acids (TFAA) (Table 2a). In comparison to C under both salinity levels (S50 and S100), a significant increase in TFAA was noted in both mungbean cultivars, while Ramzan exhibited a higher content in TFAA under all applied treatments compared to NM-92 (Figure 2D).
Exposure of mungbean plants to salinity (50 and 100 mM NaCl) resulted in a significant reduction (p < 0.05) in the chlorophyll (Chl) content compared to the control conditions, as detailed in (Table 2b). The highest chlorophyll a (Chl. a) contents were observed in C + K, followed by C > S50 + K > S50 > S100 + K and > S100 (Figure 3A). In the saline conditions, both mungbean cultivars exhibited a substantial decrease (p < 0.05) in the chlorophyll b (Chl. b) content (Table 2b). However, the implication of potassium led to a considerable increase in the chlorophyll b concentration (Figure 3B). The maximum Chl.b contents were found in C + K and S50 + K compared to C and S50, respectively. Potassium supplementation did not improve the Chl.b content in plants grown under S100 + K compared to those under S100 in both mungbean cultivars (Figure 3B). Salinity and potassium nutrition had a significant (P ≤ 0.05) impact on the total leaf chlorophyll content (Table 2b). It was the highest in the plants grown with C + K (Figure 3C). Moreover, the maximal leaf carotenoid content (Car) was noted in plants treated with S100 + K, followed by S100 > S50 + K, > and S50. In comparison to C, salinity produced an increase in carotenoids in all plants of both mungbean cultivars exposed to 50 and 100 mM NaCl. More carotenoid contents were noted when supplied with potassium nutrition (Figure 3D).

3.3. Nutrient Uptake

Among the nutrient contents of developing mungbean cultivars, salinity significantly increased the leaf sodium (Na+) content (p ≤ 0.05), as detailed in (Table 2b). The maximum Na+ concentration was observed in plants treated with S100, decreasing with a reduction in salinity and potassium-mediated nutrition, with the order S100 + K > 50 mM NaCl > S50 + K > C + K > C (Figure 4A). The mungbean cultivar Ramzan consistently maintained higher Na+ contents than NM-92. However, the salinity significantly (p ≤ 0.05) reduced the leaf nitrogen (N) contents in both mungbean cultivars (Table 2b). The minimum leaf N contents were noted for plants grown with S100, while the highest occurred in plants under C + K. The decreasing trend followed as C > S50 + K > S50 > S100 + K (Figure 4B). Mungbean cultivar NM-92 performed better than Ramzan because cultivar NM-92 maintained higher N contents than the other one. Salinity and potassium nutrition significantly influenced the leaf phosphorous (P) contents (p ≤ 0.05) in both mungbean cultivars, as indicated in (Table 2b). The phosphorous contents (P) markedly decreased (p ≤ 0.05) with increased salinity levels in the growth medium (S50 to S100) in both mungbean cultivars. The minimum P contents were noted in plants treated with S100. However, after potassium application, plants grown under C + K, S50 + K, and S100 + K showed improvement in their P content. Mungbean cultivar NM-92 maintained higher P contents compared to Ramzan (Figure 4C).
Moreover, salt stress adversely impacted the leaf potassium (K+) contents, while the addition of potassium nutrition in the growth media significantly improved this parameter in both mungbean cultivars (p ≤ 0.05) (Table 2b). Plants treated with C + K had the maximum K+ contents, which decreased with reduced salinity and increased with potassium application. The decreasing trend for the potassium content was S50 + K > C > S50 > S100. The mungbean cultivars showed different behaviors in the saline environment, with NM-92 successfully maintaining higher K+ than the cultivar Ramzan (Figure 4D). In contrast, calcium (Ca2+) and magnesium (Mg2+) contents in leaf samples of both mungbean cultivars were significantly affected by salinity and potassium nutrition (p < 0.05), as outlined in (Table 2b). Plants grown under salinity levels of 50 and 100 mM NaCl displayed a substantial reduction in leaf Ca2+ and Mg2+ contents in both mungbean cultivars in comparison to their respective controls (Figure 4E). The application of potassium significantly increased the Ca2+ and Mg2+ contents in plants grown under both control and saline conditions. The mungbean cultivars responded differently to saline conditions, with NM-92 revealing an overall higher Ca2+ + Mg2+ compared to Ramzan.

3.4. Principal Component and Heatmap Analyses

Principal component analysis (PCA) is a multivariant statistical analysis that is normally used to scrutinize a large, intricate dataset. In the current research, PCA analysis was performed individually for the mungbean cultivars to estimate the variations in the studied parameters under different applied treatments. As the vector length increases from their point of origin to the extraneous area of the constructed biplots, the variability for the corresponding parameters is enhanced. Moreover, the bar graph or scree plot played an imperative role in the better comprehension of the eigenvalues’ contribution towards the variability in all the principal components (PCs) in the PCA analysis (Figure 5). The scree plot analysis for both mungbean cultivars, i.e., NM-92 (Figure 5A) and Ramzan (Figure 5B), revealed that the first two principal components impart more contributions in the total variability for all the studied parameters under different applied treatments. Therefore, principal component analysis was accomplished among the first two principal components (Figure 5). The biplot analysis, constructed for both the NM-92 and Ramzan cultivars, showed that the control and C + K treatments were highly effective in demonstrating a synergistic coherent variation pattern among the root length (RL), chlorophyll a (Chl.a), chlorophyll b (Chl.b), total chlorophyll (T.chl), and fresh biomass per plant (FB), and divulged antagonistic variations with the total free amino acids (TFAA), carotenoids (Car), and sodium (Na) that were favored by S100 + K (Figure 6). However, a contradiction was noticed for the Ramzan cultivar, where S100 + K showed variations in the sodium (Na) content while at the salinity level S50 for the total free amino acids (TFAA) and carotenoids (Car) concentration (Figure 6B). Similarly, for the NM-92 cultivar, only the S100 + K treatment showed negative variations in TFAA, Car, and Na for the chlorophyll contents and fresh biomass (FB). For NM-92, the cumulative variability among the first two PCs was 96.74%—where PC-1 contributed 92.21%, and PC-2 revealed 4.53% (Figure 6A). Additionally, the biplot analysis for the Ramzan showed that the cumulative variability among the first two PCs was 94.82%, where PC-1 shared a 90.45% variation while PC-2 was 4.37% (Figure 6B).
Moreover, heatmap analyses were performed separately for the mungbean cultivars using R Software (version 4.3.2). The heatmap constructed for mungbean cultivar NM-92 depicted two main clusters in which all the applied treatments were grouped. In the first cluster, two treatments (control and C + K) were arranged together and demonstrated a strong positive correlation among the Chl.a, Chl.b, T.chl, N, SL, NRA, and K contents, while these treatments showed a negative association with Na, Car, and TFAA. However, in the second main cluster, two further sub-clusters were obtained. Among these two sub-clusters, the first sub-cluster grouped two treatments (S100 and S100 + K) that showed a strongly positive correlation with Na, Car, and TFAA and a negative one with the RL, SL, DB, and TSP concentrations (Figure 7A). Additionally, the second sub-cluster also grouped two treatments, namely S50 and S50 + K, which showed a slight negative linkage with FB, P, and TSP and a slight positive interaction with NiRA, NRA, and DB (Figure 7A).
Similarly, a heatmap developed for the Ramzan cultivar also showed two main clusters. In the first cluster, two treatments (S100 and S100 + K) were concerted together and indicated a strong negative relationship with RL, SL, DB, and P, whereas Na, Car, and TFAA were positively coordinated under these two treatments. Despite this, the second main cluster for the Ramzan cultivar was further divided into two sub-clusters. The first sub-cluster combined two treatments (S50 and S50 + K) that showed a slight negative correlation with RL and N, while it was marginally positive with DB, K, and NRA (Figure 7B). Moreover, in the second sub-cluster, the control and C + K were concerted together and depicted a strong positive correlation with the N, Chl.b, Chl.a, T.chl, and K contents, while a strong negative association manifested with the Na, Car, and TFAA contents (Figure 7B).

4. Discussion

Soil salinization is a global constraint for agriculture because it causes severe losses to plant growth and productivity by altering the morphological and physio-biochemical activities of the plants [27]. The prime objective of this study was to learn more about how salinity affects mungbean plant growth, how this affects the physio-biochemical and metabolic processes, and to explore the role of potassium in alleviating the negative effects of salt stress. In both mungbean cultivars, salinity reduced the shoot length (Figure 1A), root length (Figure 1B), number of leaves (Figure 1E), fresh biomass (Figure 1C), dry biomass (Figure 1D), nitrate reductase activity (Figure 2B), nitrite reductase activity (Figure 2C), total soluble proteins (Figure 2A), chlorophyll a (Figure 3A), chlorophyll b (Figure 3B), total chlorophyll (Figure 3C), nitrogen (Figure 4B), phosphorous (Figure 4C), potassium (Figure 4D), and calcium + magnesium (Figure 4E) in comparison to the control. Plants treated with potassium had the highest values for all these parameters in both mungbean cultivars. Plants treated with S100 had the lowest values for all these attributes. An increase in salinity led to a substantial decline in the root and shoot lengths of the mungbean varieties [28]. Decreased plant growth might be caused by the inhibition of cell division and expansion under saline conditions [29]. These results matched the earlier work of [30], indicating a salt concentration-dependent decline in the root and shoot lengths of mungbean cultivars. Moreover, [31] also reported similar results for wheat and citrus and [29] for pistachio. Although a plant’s height/length is a genetically controlled attribute and is regulated by several crucial genes, their expression is influenced by various biotic and abiotic factors. Reduction in root length is a strategy of plants to reduce the absorption of salts [32]. The salinity caused a reduction in the root and shoot lengths, resulting in decreased plant growth. This growth inhibition may be due to salt stress that causes ionic toxicity and a disturbance in metabolic activity, leading to a manifested disruption in photosynthetic activity; thus a decrease in growth biomass was obvious [33]. The current investigation also depicted that salinity caused a reduction in chlorophyll contents (Figure 3A–C) and nutrient imbalance (Figure 4); subsequently, a reduction in growth and biomass (Figure 1) was noticed. Ionic toxicity and an adverse osmotic effect of salinity reduce the number of leaves [34], and the findings of this study confirmed that both mungbean cultivars showed a reduction in the number of leaves per plant (Figure 1E), as well as fresh biomass (Figure 1C), and dry biomass (Figure 1D). The accumulation of Na+ and Cl− in the cytoplasm and cell walls of leaves causes a nutrient imbalance and reduction in the metabolic activities that reduce plant growth by decreasing the number of leaves, chlorophyll contents, and photosynthesis [35]. The findings of [36] provided supporting results with mungbean and citrus, respectively. The results of this investigation confirmed that the application of potassium in the growth media significantly improved the growth and biomass of both the mungbean cultivars (Figure 1) under saline conditions, which may be due to its essentiality for the regulation of metabolic and stomatal conductance necessary to maintain the photosynthesis under saline conditions [37].
A pronounced declining trend was ascertained for nitrate reductase activity (NRA) (Figure 2B) and nitrite reductase activity (NiRA) (Figure 2C) in both mungbean cultivars observed as a result of the salinity treatment. Similar results were provided by [38,39] for sorghum and cucumber, respectively. A higher salt concentration may be related to the salt-mediated generation of reactive oxygen species (ROS), which badly hampered the nitrate reductase, leading to its breakage and, ultimately, a decline in NRA [30]. However, the application of potassium improved NRA and NiRA because it increases the availability of substrate for NRA by decreasing the uptake of Cl− and increasing the NO3−, as there is an antagonistic relationship between Cl− and NO3−. Therefore, when substrate for NRA is available, the ability of substrate for NiRA increases [40]. Resultingly, a decrease in NRA and NiRA induces a reduction in the total soluble protein (Figure 2A). The literature affirmed that salinity adversely affected nitrogen metabolism [41]. Furthermore, to adjust the saline condition, the disintegration of heavy molecules (protein) into smaller molecules (total free amino acid) is a common phenomenon in plants [42]. Moreover, our results demonstrated that the escalation in total free amino acids concentration (Figure 2D), which was further enhanced due to the application of potassium in a growth medium [43], showed that the application of potassium in saline soil enables plants to adjust to a saline environment by decreasing the water and osmotic potential of plant cells.
Among the photosynthetic pigments, chlorophyll a, b, and total chlorophyll decreased due to salinity; however, the potassium application significantly improved all these attributes (Figure 3). Chlorophyll is requisite for photosynthesis and has a direct link to plant health, growth, and productivity [44]. The literature confirmed that the application of potassium is beneficial for improving chlorophyll contents and photosynthesis in plants grown in saline conditions [45]. Additionally, [46] also suggested another reason behind the reduction in total chlorophyll contents, i.e., a decrease in the synthesis of 5-aminolinolic acid, which is necessary for the synthesis of total chlorophyll.
In contrast to the control, salt stress significantly enhanced the carotenoid levels (Figure 3D) and sodium (Na+) content (Figure 4A) in both mungbean cultivars. Plants treated with S100 and the potassium application in the growth media exhibited the highest levels of carotenoids. The increase in carotenoids in plants under stress conditions is often observed by many researchers because carotenoids act as antioxidants to combat the ROS generated due to salinity [47]. Moreover, plants treated with S100 displayed the highest Na+ content; the increase in leaf Na+ contents in plants growing under saline conditions is obvious [48] because this medium contains excessive Na, which competes with Ca2+ and K+, leading to curtailed Ca2+/Na+ and K+/Na+ ratios, which affect the plant growth, yield, and other metabolic activities of the plants [49]. Therefore, the supplementation of potassium in soils containing excessive Na+ is effective in enhancing the K+/Na+ ratio, plant growth, and yield by regulating the activation of crucial genes that lead to favorable alterations in the metabolic and physio-biochemical pathways [50].
Moreover, statistical analysis (PCA, Heatmap, and ANOVA) was conducted for a better understanding of the fluctuations in the studied attributes under specific treatments of salinity. All these statistical analyses revealed that both mungbean cultivars (NM-92 and Ramzan) showed higher Chla (Figure 3A), Chlb (Figure 3B), Chlt (Figure 3C), Car (Figure 3D), FB (Figure 1C), and TSP (Figure 2A) under the control and C + K treatments, while these were negatively linked with Na (Figure 4A), Car (Figure 3D), and TFAA (Figure 2D) contents, which were increased under the S100 and S100 + K treatments. Among both Mungbean cultivars, NM-92 maintained all the studied traits higher than the Ramzan cultivar except for the TFAA and Na+ contents. The increase in chlorophyll molecules enhances photosynthetic activity, consequently activating several enzymes, such as NiRA (Figure 2C) and NRA (Figure 2B), which are essential for crop nitrogen metabolism and the synthesis of protein (TSP), both of which are necessary to improve the fresh and dry biomass (Figure 1C,D) of growing plants. These findings are strongly aligned with [51], who stated that optimum nitrogen availability improves crop growth and productivity by increasing antioxidant activity and reducing ROS concentration.
Among the nutrient contents, total nitrogen, total phosphorus, total potassium, and total Ca + Mg were high under the control and C + K treatments, and a decreasing trend was observed in the other treatments, i.e., S50 + K > S50 > S100 + K > S100; at the same time, the Na+ content was higher in the salinity stress levels. A similar trend for nutrient imbalance due to salinity was noted by [52]. In the current experiment, under saline growth media, a substantial decline in the Ca + Mg (Figure 4E) and phosphorus (Figure 4C) contents in both mungbean cultivars was recorded. Plants exposed to salinity stress suffer from oxidative damage, resulting in a reduction in water uptake in plants [53]. Furthermore, salt-stressed mungbean plants of both varieties, supplemented with potassium, enhance the competition between Na+ and K+ in the plasmalemma for absorption and maintain a high K+/Na+ ratio [54]. An optimal supply of potassium and nitrogen causes an abatement in Na+ content in sugarcane because the administration of K+ and N improves the ability of plants to evade Na+ absorption [55]. Soil salinization reduced the nitrogen in the mungbean cultivars (Figure 4B). Moreover, [56] also reported a decrease in the nitrogen content of both mungbean cultivars due to salinity stress. Possible explanations for the reduction in N content—similar to those observed in the present study under salt stress—might include the inhibition of NRA activity and a reduction in protein biosynthesis and nitrogen fixation [57], which are attended to in the current study.
In the current research activity, we utilized 0 mM, 50 mM, and 100 mM of salinity stress along with potassium alone or in combination to elucidate their interactions with mungbean crop growth and development. Moreover, the implication of potassium sulfate with different levels of salinity and potassium alone or in combined form may be a better option for improving crop growth and development. Additionally, in the era of molecular and computational biology, the exploitation of modern breeding and molecular biology tools, like marker-assisted selection (MAS), provide opportunities for omics approaches to aid in opening a new avenue for mining the vital genes and screening out mungbean genotypes that have better adaptability in diverse fluctuating environmental scenarios. It would also aid in determining the variation in growth patterns, and physio-biochemical parameters.

5. Conclusions

The findings of this investigation demonstrate that the adverse effects of salinity on the growth and biomass production of crops can be reduced by proper soil potassium nutrition management. Potassium application in saline soils alters the physio-biochemical processes, like the accumulation of total free amino acids and carotenoids, enabling plants to combat salinity through osmotic adjustment. Furthermore, the potassium nutrition management of salt-affected soils aids in promoting nitrogen metabolism by enhancing NRA, NiRA activity, and the uptake of nitrogen, potassium, phosphorous, and chlorophyll contents, leading to improvement in growth and biomass production in plants, as noticed in mungbean cultivars. Additionally, statistical analyses (PCA and Heatmap) assist in analyzing the variation and correlation among the studied parameters, indicating that Na, Car, and TFAA were positively correlated with each other but showed a strong negative correlation with all other studied attributes in both mungbean cultivars. The better-performing mungbean cultivar, NM-92, under salt stress, was due to its lower Na+ concentration and more Car contents compared to the Ramzan cultivar. Therefore, NM-92 can be grown in marginal saline soil, having salinity levels up to 50 mM or 5 dS m−1. Potassium application in saline soil plays a key role in improving crop productivity and ultimately assists in increasing the country’s economy.

Author Contributions

Conceptualization M.Y.A., R.P.M., C.C. and M.Y.S.; methodology, M.Y.S., M.N., S.A. and M.Y.A.; software, M.Y.S. and R.P.M.; validation, M.Y.A., M.Y.S., A.K.B., M.G., M.N., Z.K., F.A., A.K.B., C.C. and R.P.M.; formal analysis, R.P.M., M.Y.A., S.A., Z.K., N.G. and M.G.; investigation, M.Y.S., M.Y.A. and R.P.M.; data curation, M.Y.A., S.A., R.P.M., M.Y.S. and M.Y.S.; writing—original draft preparation, M.Y.S., M.Y.A., F.A., A.K.B. and S.A. writing—review and editing, R.P.M., C.C., M.Y.S., N.G. and M.Y.A.; visualization, M.Y.A., M.Y.S. and R.P.M.; supervision, M.Y.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Mustafa, G.; Akhtar, M.S.; Abdullah, R. Global concern for salinity on various agro-ecosystems. In Salt Stress, Microbes, and Plant Interactions: Causes and Solution; Akhtar, M., Ed.; Springer: Singapore, 2019; pp. 1–19. [Google Scholar]
  2. Montanarella, L.; Badraoui, M.; Chude, V.; Costa, I.; Mamo, T.; Yemefack, M.; Aulang, M.; Yagi, K.; Hong, S.Y.; Vijarnsorn, P. Status of the World’s Soil Resources: Main Report; Food and Agriculture Organization of the United Nation: Rome, Italy, 2015. [Google Scholar]
  3. Hussain, S.; Shaukat, M.; Ashraf, M.; Zhu, C.; Jin, Q.; Zhang, J.J.C. Salinity stress in arid and semi-arid climates: Effects and management in field crops. Clim. Change Agric. 2019, 13, 201–226. [Google Scholar]
  4. Mukhopadhyay, R.; Sarkar, B.; Jat, H.S.; Sharma, P.C.; Bolan, N.S. Soil salinity under climate change: Challenges for sustainable agriculture and food security. J. Environ. Manag. 2021, 280, 111736. [Google Scholar] [CrossRef] [PubMed]
  5. Manjunatha, P.; Harisha, R.; Kohli, M.; Naik, P.K.; Sagar, S.; Shashidhar, B.; Patel, M.K.; Ganesh, B.T.; Madhusudhan, B.; Chethan Kumar, K.J. Exploring the World of Mungbean: Uncovering its Origins, Taxonomy, Genetic Resources and Research Approaches. Int. J. Plant Soil Sci. 2023, 35, 614–635. [Google Scholar] [CrossRef]
  6. Matloob, A.; Jabran, K.; Farooq, M.; Khaliq, A.; Aslam, F.; Abbas, T.; Ehsanullah; Zaman, U.; Irshad, S.; Chauhan, B.S. Water-Wise Cultivation of Basmati Rice in Pakistan. In Modern Techniques of Rice Crop Production; Springer: Singapore, 2022; pp. 187–229. [Google Scholar]
  7. Ashraf, M.Y.; Zaib-UN-Nisa, N.; Shani, M.Y.; Naz, A.; Azmat, M.; Ashraf, I. Salicylic acid seed priming improved dry biomass and ionic efficiency of mungbean [Vigna radiata (L) wilczek] under salt stress conditions. Pak. J. Bot. 2023, 55, 1605–1613. [Google Scholar] [CrossRef] [PubMed]
  8. Xiang, W.; Wang, H.-W.; Sun, D.-W.J. Phytohormones in postharvest storage of fruit and vegetables: Mechanisms and applications. Crit. Rev. Food Sci. Nutr. 2021, 61, 2969–2983. [Google Scholar] [CrossRef]
  9. Maitra, S.; Brestic, M.; Bhadra, P.; Shankar, T.; Praharaj, S.; Palai, J.B.; Shah, M.M.R.; Barek, V.; Ondrisik, P.; Skalický, M.; et al. Bioinoculants—Natural biological resources for sustainable plant production. Microorganisms 2021, 10, 51. [Google Scholar] [CrossRef] [PubMed]
  10. Rakhmankulova, Z.; Shuyskaya, E.; Toderich, K.; Voronin, P. Elevated atmospheric CO2 concentration improved C4 xero-halophyte Kochia prostrata physiological performance under saline conditions. Plants 2021, 10, 491. [Google Scholar] [CrossRef] [PubMed]
  11. Yusuf, M.; Fariduddin, Q.; Khan, T.A.; Hayat, S. Epibrassinolide reverses the stress generated by combination of excess aluminum and salt in two wheat cultivars through altered proline metabolism and antioxidants. S. Afr. J. Bot. 2017, 112, 391–398. [Google Scholar] [CrossRef]
  12. Sharma, I.; Ching, E.; Saini, S.; Bhardwaj, R.; Pati, P.K. Exogenous application of brassinosteroid offers tolerance to salinity by altering stress responses in rice variety Pusa Basmati-1. Plant Physiol. Biochem. 2013, 69, 17–26. [Google Scholar] [CrossRef]
  13. Nasrallah, A.K.; Kheder, A.A.; Kord, M.A.; Fouad, A.S.; El-Mogy, M.M.; Atia, M.A. Mitigation of salinity stress effects on broad bean productivity using calcium phosphate nanoparticles application. Horticulturae 2022, 8, 75. [Google Scholar] [CrossRef]
  14. Etesami, H.; Alikhani, H.A. Halotolerant plant growth-promoting fungi and bacteria as an alternative strategy for improving nutrient availability to salinity-stressed crop plants. In Saline Soil-Based Agriculture by Halotolerant Microorganisms; Springer: Singapore, 2019; pp. 103–146. [Google Scholar]
  15. Ketehouli, T.; Idrice Carther, K.F.; Noman, M.; Wang, F.-W.; Li, X.-W.; Li, H.Y. Adaptation of plants to salt stress: Characterization of Na+ and K+ transporters and role of CBL gene family in regulating salt stress response. Agronomy 2019, 9, 687. [Google Scholar] [CrossRef]
  16. Evelin, H.; Devi, T.S.; Gupta, S.; Kapoor, R. Mitigation of salinity stress in plants by arbuscular mycorrhizal symbiosis: Current understanding and new challenges. Front. Plant Sci. 2019, 10, 450967. [Google Scholar] [CrossRef] [PubMed]
  17. Sym, G.J. Optimisation of the in-vivo assay conditions for nitrate reductase in barley (Hordeum vulgare L. cv. Igri). J. Sci. Food Agric. 1984, 35, 725–730. [Google Scholar] [CrossRef]
  18. Ramarao, C.; Patil, V.; Dhak, B.; Kadrekar, S.B. A simple in vivo method for the determination of nitrite reductase activity in rice roots. Z. Pflanzenphysiol. 1983, 109, 81–85. [Google Scholar] [CrossRef]
  19. Hamilton, P.; Van Slyke, D.J. Amino acid determination with ninhydrin. J. Biol. Chem. 1943, 150, 231–250. [Google Scholar] [CrossRef]
  20. Lowry, O.H.; Rosebrough, N.J.; Farr, A.L.; Randall, R.J. Protein measurement with the Folin phenol reagent. J. Biol. Chem. 1951, 193, 265–275. [Google Scholar] [CrossRef] [PubMed]
  21. Arnon, D.I. Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta vulgaris. Plant Physiol. 1949, 24, 1. [Google Scholar] [CrossRef] [PubMed]
  22. Davies, B. Carotenoids in higher plants. In Lipids and Lipid Polymers in Higher Plants; Springer: Berlin/Heidelberg, Germany, 1977; pp. 199–217. [Google Scholar]
  23. Lowther, J.R. Use of a single sulphuric acid-hydrogen peroxide digest for the analysis of Pinus radiata needles. Commun. Soil Sci. Plant Anal. 1980, 11, 175–188. [Google Scholar] [CrossRef]
  24. Hide, J.J.S. Diagnosis and Improvement of Saline and Alkali Soils; US Salinity Laboratory Staff; Richards, L.A., Ed.; US Department of Agriculture: Washington, DC, USA, 1954; 160p.
  25. Bremner, J.M. Determination of nitrogen in soil by the Kjeldahl method. J. Agric. Sci. 1960, 55, 11–33. [Google Scholar] [CrossRef]
  26. Chang, S.; Jackson, M.L. Soil Phosphorus Fractions in some representative soils 1. J. Soil Sci. 1958, 9, 109–119. [Google Scholar] [CrossRef]
  27. Ramzan, F.; Younis, A. Use of biostimulants in tolerance of drought stress in agricultural crops. In Emerging Plant Growth Regulators in Agriculture; Academic Press: Cambridge, MA, USA, 2022; pp. 429–446. [Google Scholar]
  28. Dutta, P.; Bera, A.K. Effect of NaCl salinity on seed germination and seedling growth of mungbean cultivars. Legume Res.-Int. J. 2014, 37, 161–164. [Google Scholar] [CrossRef]
  29. Rahneshan, Z.; Nasibi, F.; Moghadam, A.A. Effects of salinity stress on some growth, physiological, biochemical parameters and nutrients in two pistachio (Pistacia vera L.) rootstocks. J. Plant Interact. 2018, 13, 73–82. [Google Scholar] [CrossRef]
  30. Alharbi, K.; Al-Osaimi, A.A.; Alghamdi, B.A. Sodium chloride (NaCl)-induced physiological alteration and oxidative stress generation in Pisum sativum (L.): A toxicity assessment. ACS Omega 2022, 7, 20819–20832. [Google Scholar] [CrossRef] [PubMed]
  31. Ashraf, M.Y.; Rafique, N.; Ashraf, M.; Azhar, N.; Marchand, M. Effect of supplemental potassium (K+) on growth, physiological and biochemical attributes of wheat grown under saline conditions. J. Plant Nutr. 2013, 36, 443–458. [Google Scholar] [CrossRef]
  32. Alharbi, B.M.; Elhakem, A.H.; Alnusairi, G.S.; Soliman, M.H.; Hakeem, K.R.; Hasan, M.M.; Abdelhamid, M.T. Exogenous application of melatonin alleviates salt stress-induced decline in growth and photosynthesis in Glycine max (L.) seedlings by improving mineral uptake, antioxidant and glyoxalase system. Plant Soil Environ. 2021, 67, 208–220. [Google Scholar] [CrossRef]
  33. Arif, Y.; Singh, P.; Siddiqui, H.; Bajguz, A.; Hayat, S. Salinity induced physiological and biochemical changes in plants: An omic approach towards salt stress tolerance. Plant Physiol. Biochem. 2020, 156, 64–77. [Google Scholar] [CrossRef] [PubMed]
  34. Ayub, Q.; Khan, S.M.; Hussain, I.; Gurmani, A.R.; Naveed, K.; Mehmood, A.; Ali, S.; Ahmad, T.; Haq, N.; Hussain, A. Mitigating the adverse effects of NaCl salinity on pod yield and ionic attributes of okra plants by silicon and gibberellic acid application. Italus Hortus 2021, 28, 1–59. [Google Scholar] [CrossRef]
  35. Abbas, S.; Javed, M.T.; Ali, Q.; Azeem, M.; Ali, S. Nutrient deficiency stress and relation with plant growth and development. In Engineering Tolerance in Crop Plants against Abiotic Stress; CRC Press: Boca Raton, FL, USA, 2021; pp. 239–262. [Google Scholar]
  36. Hyder, S.; Gondal, A.S.; Rizvi, Z.F.; Iqbal, R.; Hannan, A.; Sahi, S.T. Antagonism of selected fungal species against Macrophomina phaseolina (Tassi) goid, causing charcoal rot of Mungbean. Pak. J. Bot. 2022, 54, 1129–1138. [Google Scholar] [CrossRef]
  37. Liu, B.; Soundararajan, P.; Manivannan, A. Mechanisms of silicon-mediated amelioration of salt stress in plants. Plants 2019, 8, 307. [Google Scholar] [CrossRef]
  38. Singh, R.B.; Rao, V.P.; Sengar, R.S. Study of salinity induced oxidative stress and antioxidant responses in callus cultures of sugarcane. Ecol. Genet. Genom. 2023, 26, 100164. [Google Scholar]
  39. Hesari, N.; Szegő, A.; Mirmazloum, I.; Pónya, Z.; Kiss-Bába, E.; Kolozs, H.; Gyöngyik, M.; Vasas, D.; Papp, I. High-nitrate-supply-induced transcriptional upregulation of ascorbic acid biosynthetic and recycling pathways in cucumber. Plants 2023, 12, 1292. [Google Scholar] [CrossRef] [PubMed]
  40. Mbarki, S.; Sytar, O.; Cerda, A.; Zivcak, M.; Rastogi, A.; He, X.; Zoghlami, A.; Abdelly, C.; Brestic, M. Strategies to mitigate the salt stress effects on photosynthetic apparatus and productivity of crop plants. In Salinity Responses and Tolerance in Plants, Volume 1: Targeting Sensory, Transport and Signaling Mechanisms; Springer: Cham, Switzerland, 2018; pp. 85–136. [Google Scholar]
  41. Dubey, R.S.; Srivastava, R.K.; Pessarakli, M. Physiological mechanisms of nitrogen absorption and assimilation in plants under stressful conditions. In Handbook of Plant and Crop Physiology; CRC Press: Boca Raton, FL, USA, 2021; pp. 579–616. [Google Scholar]
  42. Anwar, T.; Qureshi, H.; Fatimah, H.; Siddiqi, E.H.; Anwaar, S.; Moussa, I.M.; Adil, M.F. Elucidating effect of ZnO-Nanoparticles and melatonin on physiological adjustments and growth of Solanum melongena under salinity stress. Horticulturae 2023, 322, 112455. [Google Scholar] [CrossRef]
  43. El-Beltagi, H.S.; Ahmed, S.H.; Namich, A.A.M.; Abdel-Sattar, R.R. Effect of salicylic acid and potassium citrate on cotton plant under salt stress. Fresenius Environ. Bull. 2017, 26, 1091–1100. [Google Scholar]
  44. Lysenko, V.; Rajput, V.D.; Kumar Singh, R.; Guo, Y.; Kosolapov, A.; Usova, E.; Varduny, T.; Chalenko, E.; Yadronova, O.; Dmitriev, P.; et al. Chlorophyll fluorometry in evaluating photosynthetic performance: Key limitations, possibilities, perspectives and alternatives. Physiol. Mol. Biol. Plants 2022, 28, 2041–2056. [Google Scholar] [CrossRef] [PubMed]
  45. Zafar, S.; Ashraf, M.Y.; Saleem, M. Shift in physiological and biochemical processes in wheat supplied with zinc and potassium under saline condition. J. Plant Nutr. 2018, 41, 19–28. [Google Scholar] [CrossRef]
  46. Ashraf, M.Y.; Tariq, S.; Saleem, M.; Khan, M.A.; Hassan, S.W.U.; Sadef, Y. Calcium and zinc mediated growth and physio-biochemical changes in mungbean grown under saline conditions. J. Plant Nutr. 2020, 43, 512–525. [Google Scholar] [CrossRef]
  47. Ahmad, R.; Hussain, S.; Anjum, M.A.; Khalid, M.F.; Saqib, M.; Zakir, I.; Hassan, A.; Fahad, S.; Ahmad, S. Oxidative stress and antioxidant defense mechanisms in plants under salt stress. In Plant Abiotic Stress Tolerance: Agronomic, Molecular and Biotechnological Approaches; Springer: Cham, Switzerland, 2019; pp. 191–205. [Google Scholar]
  48. Mostofa, M.G.; Saegusa, D.; Fujita, M.; Tran, L.S.P. Hydrogen sulfide regulates salt tolerance in rice by maintaining Na+/K+ balance, mineral homeostasis and oxidative metabolism under excessive salt stress. Front. Plant Sci. 2015, 6, 171620. [Google Scholar] [CrossRef] [PubMed]
  49. Hussain, Z.; Khattak, R.; Irshad, M.; Mahmood, Q.; An, P. Effect of saline irrigation water on the leachability of salts, growth and chemical composition of wheat (Triticum aestivum L.) in saline-sodic soil supplemented with phosphorus and potassium. J. Soil Sci. Plant Nutr. 2016, 16, 604–620. [Google Scholar] [CrossRef]
  50. Johnson, R.; Vishwakarma, K.; Hossen, M.S.; Kumar, V.; Shackira, A.; Puthur, J.T.; Abdi, G.; Sarraf, M.; Hasanuzzaman, M. Potassium in plants: Growth regulation, signaling, and environmental stress tolerance. Plant Physiol. Biochem. 2022, 172, 56–69. [Google Scholar] [CrossRef]
  51. Rehman, M.; Yang, M.; Fahad, S.; Saleem, M.H.; Liu, L.; Liu, F.; Deng, G. Morpho-physiological traits, antioxidant capacity, and nitrogen metabolism in ramie under nitrogen fertilizer. Agron. J. 2020, 112, 2988–2997. [Google Scholar] [CrossRef]
  52. Okon, O.G. Effect of salinity on physiological processes in plants. In Microorganisms in Saline Environments: Strategies and Functions; Springer: Cham, Switzerland, 2019; pp. 237–262. [Google Scholar]
  53. Rehman, S.; Abbas, G.; Shahid, M.; Saqib, M.; Farooq, A.B.U.; Hussain, M.; Murtaza, B.; Amjad, M.; Naeem, M.A.; Farooq, A. Effect of salinity on cadmium tolerance, ionic homeostasis and oxidative stress responses in conocarpus exposed to cadmium stress: Implications for phytoremediation. Ecotoxicol. Environ. Saf. 2019, 171, 146–153. [Google Scholar] [CrossRef] [PubMed]
  54. Selvakumar, G.; Shagol, C.C.; Kim, K.; Han, S.; Sa, T. Spore associated bacteria regulates maize root K+/Na+ ion homeostasis to promote salinity tolerance during arbuscular mycorrhizal symbiosis. BMC Plant Biol. 2018, 18, 109. [Google Scholar] [CrossRef] [PubMed]
  55. Mekdad, A.A.; Shaaban, A.; Rady, M.M.; Ali, E.F.; Hassan, F.A. Integrated application of K and Zn as an avenue to promote sugar beet yield, industrial sugar quality, and K-use efficiency in a salty semi-arid agro-ecosystem. Agronomy 2021, 11, 780. [Google Scholar] [CrossRef]
  56. Podder, S.; Ray, J.; Das, D.; Sarker, B.C. Effect of salinity (NaCl) on germination and seedling growth of mungbean (Vigna radiata L.). J. Biosci. Agric. Res. 2020, 24, 2012–2019. [Google Scholar] [CrossRef]
  57. Fiaz, M.; Ahmed, I.; Hassan, S.M.U.; Niazi, A.K.; Khokhar, M.F.; Farooq, M.A.; Arshad, M. Antibiotics induced changes in nitrogen metabolism and antioxidative enzymes in mung bean (Vigna radiata). Sci. Total Environ. 2023, 873, 162449. [Google Scholar] [CrossRef]
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Figure 1. Potassium nutrition induced alterations in shoot length (A), root length (B), fresh biomass (C), dry biomass (D), and number of leaves (E) per plant of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters indicate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
Figure 1. Potassium nutrition induced alterations in shoot length (A), root length (B), fresh biomass (C), dry biomass (D), and number of leaves (E) per plant of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters indicate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
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Figure 2. Potassium nutrition induced alterations in total soluble proteins (A), nitrate reductase activity (B), nitrite reductase activity (C), and total free amino acids (D) of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters reveal significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
Figure 2. Potassium nutrition induced alterations in total soluble proteins (A), nitrate reductase activity (B), nitrite reductase activity (C), and total free amino acids (D) of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters reveal significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
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Figure 3. Potassium nutrition induced alterations in chlorophyll a (A), chlorophyll b (B), total chlorophylls (C), and carotenoids (D) contents of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters demonstrate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
Figure 3. Potassium nutrition induced alterations in chlorophyll a (A), chlorophyll b (B), total chlorophylls (C), and carotenoids (D) contents of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters demonstrate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
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Figure 4. Potassium nutrition induced alterations in total sodium (A), total nitrogen (B), total phosphorus (C), total potassium (D), and total (Ca + Mg) (E) contents of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters indicate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
Figure 4. Potassium nutrition induced alterations in total sodium (A), total nitrogen (B), total phosphorus (C), total potassium (D), and total (Ca + Mg) (E) contents of two mungbean cultivars (NM-92 and Ramzan) grown under normal and saline conditions. Different letters indicate significant differences as per Tukey’s HSD test (p ≤ 0.05) between cultivars under potassium and salinity treatments. Vertical bars indicate the standard error of the mean.
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Figure 5. A bar graph or scree plot indicating eigenvalues on the y-axis and factors (y-axis) for all the principal components of studied mungbean cultivars: (A) NM-92 and (B) Ramzan grown under normal and saline conditions.
Figure 5. A bar graph or scree plot indicating eigenvalues on the y-axis and factors (y-axis) for all the principal components of studied mungbean cultivars: (A) NM-92 and (B) Ramzan grown under normal and saline conditions.
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Figure 6. Principal component analysis (Biplot) for two mungbean cultivars: (A) NM−92 and (B) Ramzan, grown under normal and saline conditions.
Figure 6. Principal component analysis (Biplot) for two mungbean cultivars: (A) NM−92 and (B) Ramzan, grown under normal and saline conditions.
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Figure 7. Heatmap correlation analysis on two mungbean cultivars: (A) NM−92 and (B) Ramzan, grown under normal and saline conditions.
Figure 7. Heatmap correlation analysis on two mungbean cultivars: (A) NM−92 and (B) Ramzan, grown under normal and saline conditions.
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Table 1. (a) Treatment details conducted during the experiment. (b) Composition of 100% Hoagland’s nutrient solution.
Table 1. (a) Treatment details conducted during the experiment. (b) Composition of 100% Hoagland’s nutrient solution.
(a)
Sr. no#Treatment DescriptionDesignationConcentration of NaCl/K2SO4
1.ControlC0 mM NaCl + 0 mM K2SO4
2.Control + Potassium sulfateC + K0 mM NaCl + 50 mM K2SO4
3.Salinity (50 mM NaCl)S5050 mM NaCl + 0 mM K2SO4
4.Salinity (50 mM NaCl) + Potassium sulfateS50 + K50 mM NaCl + 50 mM K2SO4
5.Salinity (100 mM NaCl)S100100 mM NaCl + 0 mM K2SO4
6.Salinity (100 mM NaCl) + Potassium sulfateS100 + K100 mM NaCl + 50 mM K2SO4
(b)
ContentsComposition of Stock SolutionConcentration per Liter
MgSO4·7H2O24.6 g/100 mL2 mL/L
Ca(NO3)2·4H2O23.6 g/100 mL5 mL/L
KH2PO413.6 g/100 mL1 mL/L
KNO310.1 g/100 mL5 mL/L
H3BO32.86 g/L1 mL/L
MnCl2·4H2O1.82 g/L1 mL/L
ZnSO4·7H2O0.22 g/L1 mL/L
CuSO4·5H2O0.09 g/L1 mL/L
MoO30.01 g/L1 mL/L
Fe-DTPA 50.0 mg/L
Table 2. (a) Mean square values showing the effect of potassium nutrition on different parameters of mungbean varieties grown in saline conditions. (b) Mean square values show the effect of potassium nutrition on different parameters of mungbean varieties grown in saline conditions.
Table 2. (a) Mean square values showing the effect of potassium nutrition on different parameters of mungbean varieties grown in saline conditions. (b) Mean square values show the effect of potassium nutrition on different parameters of mungbean varieties grown in saline conditions.
(a)
SourceDFSLRLNOLFBDBNiRANRATFAATSP
Variety112.48 ***10.53 ***2.66 **3.14 ***0.012 NS4.73 ***4.58 ***55.70 ***52.76 ***
Treatment512.48 ***11.49 ***3.68 ***3.68 ***0.368 ***1.98 ***2.103 ***41.74 ***7.904 ***
Variety × Treatment 50.50 *0.07 NS0.10 NS0.002 NS0.039 NS0.19 ***0.13 ***0.67 **0.011 NS
Error240.150.120.060.0140.0180.0120.0070.120.024
(b)
SourceDFChl. aChl. bT.ChlCarNPKNa(Ca + Mg)
Variety10.26 ***0.205 ***0.929 ***12.26 ***0.419 ***0.358 ***25.00 ***131.45 ***0.366 ***
Treatment50.067 ***0.052 ***0.236 ***4.15 ***0.355 ***5.589 ***71.23 ***174.70 ***5.126 ***
Variety × Treatment 50.0001 NS0.002 **0.0025 NS0.03 NS0.004 **0.112 **1.46 *1.048 ***0.1005 **
Error240.00040.00030.0010.0140.00070.0220.380.1080.024
SL: shoot length; RL: root length; NOL: number of leaves; FB: fresh biomass per plant; DB: dry biomass per plant; NiRA: nitrite reductase activity; NRA: nitrate reductase activity; TFAA: total free amino acids; TSP: total soluble proteins. Chl. a: chlorophyll a content; Chl. b: chlorophyll b content; T. chl.: total chlorophyll; Car: total carotenoids contents; N: total nitrogen; P: total phosphorus; K: total potassium; Na: total sodium content. *, **, and ***: significant at p ≤ 0.05, 0.01, and 0.001, respectively. NS: not significant.
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MDPI and ACS Style

Shani, M.Y.; Ashraf, M.Y.; Butt, A.K.; Abbas, S.; Nasif, M.; Khan, Z.; Mauro, R.P.; Cannata, C.; Gul, N.; Ghaffar, M.; et al. Potassium Nutrition Induced Salinity Mitigation in Mungbean [Vigna radiata (L.) Wilczek] by Altering Biomass and Physio-Biochemical Processes. Horticulturae 2024, 10, 549. https://doi.org/10.3390/horticulturae10060549

AMA Style

Shani MY, Ashraf MY, Butt AK, Abbas S, Nasif M, Khan Z, Mauro RP, Cannata C, Gul N, Ghaffar M, et al. Potassium Nutrition Induced Salinity Mitigation in Mungbean [Vigna radiata (L.) Wilczek] by Altering Biomass and Physio-Biochemical Processes. Horticulturae. 2024; 10(6):549. https://doi.org/10.3390/horticulturae10060549

Chicago/Turabian Style

Shani, Muhammad Yousaf, M. Yasin Ashraf, Ammara Khalid Butt, Shahid Abbas, Muhammad Nasif, Zafran Khan, Rosario Paolo Mauro, Claudio Cannata, Nimra Gul, Maria Ghaffar, and et al. 2024. "Potassium Nutrition Induced Salinity Mitigation in Mungbean [Vigna radiata (L.) Wilczek] by Altering Biomass and Physio-Biochemical Processes" Horticulturae 10, no. 6: 549. https://doi.org/10.3390/horticulturae10060549

APA Style

Shani, M. Y., Ashraf, M. Y., Butt, A. K., Abbas, S., Nasif, M., Khan, Z., Mauro, R. P., Cannata, C., Gul, N., Ghaffar, M., & Amin, F. (2024). Potassium Nutrition Induced Salinity Mitigation in Mungbean [Vigna radiata (L.) Wilczek] by Altering Biomass and Physio-Biochemical Processes. Horticulturae, 10(6), 549. https://doi.org/10.3390/horticulturae10060549

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