Next Article in Journal
Study on the Impact of the Healthy Cities Pilot Policy on Industrial Structure Upgrading: Quasi-Experimental Evidence from China
Next Article in Special Issue
Accumulation of Heavy Metals, Yield and Nutritional Composition of Potato (Solanum tuberosum L.) Cultivars Irrigated with Fly-Ash-Treated Acid Mine Drainage
Previous Article in Journal
Future Projection of Precipitation Bioclimatic Indicators over Southeast Asia Using CMIP6
Previous Article in Special Issue
Screening Technique Based on Seed and Early Seedling Parameters for Cold Tolerance of Selected F2-Derived F3 Rice Genotypes under Controlled Conditions
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Sustainability
Volume 14
Issue 20
10.3390/su142013579
sustainability-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Proline-Induced Modifications in Morpho-Physiological, Biochemical and Yield Attributes of Pea (Pisum sativum L.) Cultivars under Salt Stress

by
Sadia Shahid
1,
Muhammad Shahbaz
1,
Muhammad Faisal Maqsood
2,
Fozia Farhat
3,*,
Usman Zulfiqar
4,
Talha Javed
5,6,*,
Muhammad Fraz Ali
5,
Majid Alhomrani
7,8 and
Abdulhakeem S. Alamri
7,8
1
Department of Botany, University of Agriculture, Faisalabad 38000, Pakistan
2
Department of Botany, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
3
Department of Botany, Government College Women University, Faisalabad 38000, Pakistan
4
Department of Agronomy, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
5
Department of Agronomy, University of Agriculture, Faisalabad 38040, Pakistan
6
College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou 350002, China
7
Department of Clinical Laboratories Sciences, The Faculty of Applied Medical Sciences, Taif University, Taif 21944, Saudi Arabia
8
Centre of Biomedical Sciences Research (CBSR), Deanship of Scientific Research, Taif University, Taif 21944, Saudi Arabia
*
Authors to whom correspondence should be addressed.
Sustainability 2022, 14(20), 13579; https://doi.org/10.3390/su142013579
Submission received: 22 September 2022 / Revised: 14 October 2022 / Accepted: 18 October 2022 / Published: 20 October 2022
(This article belongs to the Special Issue Sustainable Agricultural Approaches in Developing Climate Smart Crops)
Browse Figures
Review Reports Versions Notes

Abstract

:
Climate change is aggravating soil salinity, causing huge crop losses around the globe. Multiple physiological and biochemical pathways determine the ability of plants to tolerate salt stress. A pot experiment was performed to understand the impact of proline levels, i.e., 0, 10, 20 mM on growth, biochemical and yield attributes of two pea (Pisum sativum L.) cultivars (cv. L-888 and cv. Round) under salt stress (150 mM) along with control (0 mM; no stress). The pots were filled with river-washed sand; all the plants were irrigated with full-strength Hoagland’s nutrient solution and grown for two weeks before application of salt stress. Foliar spray of proline was applied to 46-day-old pea plants, once a week till harvest. Data for various growth and physio-biochemical attributes were collected from 70-day-old pea plants. Imposition of salt stress significantly checked growth, gas exchange characteristics [net CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (gs)], total soluble proteins, concentration of superoxide dismutase (SOD), shoot and root K+ and Ca2+ contents, while sub-stomatal CO2 concentration (Ci), coefficient of non-photochemical quenching (qN), non-photochemical quenching (NPQ), concentration of catalase (CAT) and peroxidase (POD), free proline, and shoot and root Na+ contents increased substantially. Foliar application of proline significantly improved growth, yield, A, gs, activity of POD, and shoot and root K+ and Ca2+ contents, while decreased NPQ values in both pea cultivars under stress and non-stress conditions. Moreover, both pea cultivars showed significant differences as cv. Round exhibited a higher rate of growth, yield, gas exchange, soluble proteins, CAT activity, free proline, shoot and root K+ and Ca2+ contents compared to L-888. Hence, the outcomes of this study pave the way toward the usage of proline at 20 mM, and cv. Round may be recommended for saline soil cultivation.

1. Introduction

Salinity or salinization (especially secondary salinization) is not a recent global phenomenon resulting from expanding urbanization, industrialization or the modernization of agriculture, but an age-old problem of irrigated agriculture [1]. However, salinity is becoming more severe with the expanding population and displays serious threats to land under cultivation around the globe, reducing the capacity of all forms of the terrestrial ecosystems by lowering our biodiversity, agricultural productivity, damaging the environment, contaminating groundwater, creating flood risks and food security issues, and limiting the economic growth of a community [2]. About 33% of cultivated lands are categorized as salt-affected soil, which may increase up to 50% by 2050 [3]. This trend grows antagonistic with the ever-increasing challenge of ensuring global food security, and so creates an emergent situation in which there is a need to search for more cultivated land and enhance crop productivity even in barren soil by establishing efficient and tolerant crops capable of growing in salty conditions [4,5]. The global agriculture sector currently encounters many challenges, including the production of 70% more food to ensure food security [6]. In many situations, lower productivity is caused by various environmental stresses [7]. The more intricately regulated stresses such as high salinity, drought, cold, and heat have a negative effect on the survival, development, biomass and yield of economically important food crops [8].
The over-accumulation of salinity in the plant’s rhizosphere, which imposes highly deleterious effects on plant biomass [9], physiology [10], accumulation of mineral ions [11,12], damage PSII reaction centers [13], and metabolic dysfunction because of production of reactive oxygen species (ROS), leads to growth retardation with substantial loss of metabolic functioning of the plant [14]. Notably, many plants attempt to balance both enzymatic and non-enzymatic antioxidant defense systems under extreme salinity stresses [15].
Pea (Pisum sativum L.) is a leguminous crop that is cultivated in tropical and sub-tropical areas of the world [16]. It is a cool season vegetable crop that is used as food and fodder throughout the country. The pea is an excellent source of various vitamins, minerals, antioxidants, salts, carbohydrates and proteins [17]. The field pea is a highly significant pulse crop. Canada was ranked first in area (21%) and production (35%) at global level, while China occupies the second position in area (13.70%), followed by Russia (12.94%). It is worth mentioning that in spite of low area utilized for pea cultivation, Ireland has the highest productivity (5000 kg ha−1), followed by the Netherlands (4766 kg ha−1), and Denmark (4048 kg ha−1). In developed countries, the field pea is grown on industrial scale, whereas in developing countries, these are grown on subsistence level and considered a staple food [18].
The pea is known to possess moderate tolerance to salinity stress [19]. Among various environmental constraints, soil salinity adversely affects growth, gas exchange, activities of antioxidant enzymes and mineral nutrients of pea plants [20]. The high concentration of antioxidants under salt stress conditions can cause damage and correlate it significantly with plant tolerance against stress [21]. Similarly, salinity could also result in the display of many other abiotic stresses and different physiological abnormalities in plants [22]. Exogenous application of low molecular weight compounds such as glycine betaine and proline can reduce damaging effects of salt stress by enhancing plant’s tolerance against abiotic stresses [23,24]. These molecules rescue the plants and regulate osmotic adjustment to enhance salt stress tolerance in plants [25]. Proline acts as an osmolyte, a metal chelator and a signaling molecule. Proline maintains the structure of membranes, prevents electrolyte leakage and reduces the level of reactive oxygen species [26,27]. Proline reduces membrane damages by decreasing oxidative stress attributes such as MDA contents in cucumber [28] and H2O2 [29]. These molecules help the plants to regulate osmotic adjustment and to enhance abiotic stress tolerance in plants. Exogenous application of proline enhances stress tolerance in different food crops when applied in an appropriate concentration e.g., cucumber (Cucumis sativus L.) [30], rice (Oryza sativa L.) [31,32], wheat (Triticum aestivum L.) [33], and sunflower (Helianthus annuus L.) [34].
Proline has a diversified role in plants, particularly under stressful conditions. However, there is no or very little information available about foliar application of proline on pea plants under salt stress. Regarding the significance of proline, it is hypothesized that foliar application of proline could mitigate deleterious effects of salt stress and enhance growth, gas exchange, chlorophyll fluorescence, antioxidant defense systems, mineral nutrients and yield potential of pea plants under saline or non-saline conditions. Furthermore, the different levels of proline were critically analyzed on pea plants with and without salt stress proline.

2. Materials and Methods

In order to investigate the effect of foliar application of proline on two pea cultivars (L-888 and Round), a pot experiment was conducted under natural climatic conditions at the University of Agriculture, Faisalabad, Punjab, Pakistan. Seeds of two cultivars were obtained from Ayub Agricultural Research Institute (AARI), Faisalabad, Punjab, Pakistan. Round pots with specific dimensions (top width, 27 cm; bottom width, 20.5 cm) were used for the current project. There were six sets of 36 pots: one set for control, the second set for 10 mM Pro application, the third set for 20 mM Pro application, the fourth set for salt stress, the fifth set of salt + 10 mM Pro, and the sixth set for salt + 20 mM Pro. Eight seeds were sown in each plastic pot in thoroughly washed river sand (5.5 kg per pot). After germination, 5 seedlings per pot were maintained. Plants were nourished with full-strength Hoagland’s nutrient solution to attain the plant’s essential nutritional requirements until the application of salt stress (i.e., 14 days). After two weeks of germination, two regimes of salt stress were maintained as non-saline. Only full-strength Hoagland’s nutrient solution and saline (150 mM NaCl in full strength Hoagland’s nutrient solution) were applied and continued until the harvest. Salinity level (150 mM) in the rhizosphere was achieved by gradually increasing the salt concentration in aliquots of 50 mM NaCl for three days to avoid osmotic shock. Proline (Mol. wt. 115.11; Sigma Aldrich, Waltham, MA, USA), was used for making the different proline concentrations (0, 10 and 20 mM + 0.1% tween-20). Proline solutions were prepared according to standard protocol. A stock solution of proline (30 mM) was prepared in deionized water, later diluted to desired concentration for the experiment. Tween-20 was used as surfactant. Foliar application of three proline levels was performed at 25 mL per pot to 56-day-old pea plants. Design of experiment was completely randomized with four replicates. Fresh leaf samples of 70-day-old pea plants were collected in plastic zipper bags, stored at −20 °C and used for the determination of various growth and physicochemical attributes.

2.1. Determination of Growth Attributes

Two plants from each pot were carefully uprooted; their shoot/root lengths and fresh weights were measured. The plants were oven-dried at 65 °C up to their constant dry weight.

2.2. Gas Exchange Characteristics

Infrared gas analyzer (IRGA) of Analytical Development Company, LCA-4 ADC, Hoddesdon, was used for the determination of gas-exchange characteristics such as net CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (gs) and sub-stomatal CO2 (Ci). Data were recorded according to the specifications as described in [35] from 11:00 a.m. to 01:00 p.m. with Qleaf (PAR) value as 942 µmol m−2s−1.

2.3. Determination of Chlorophyll Fluorescence Attributes

For the determination of chlorophyll fluorescence attributes, a multi-mode chlorophyll fluorometer (OS5P-Sciences, Inc. Winn Avenue, Hudson, NH, USA) was used according to the method of [36] with specifications as described by Nusrat [20].

2.4. Determination of Soluble Proteins

Total soluble protein contents in fresh leaf samples were determined by the [37]. Leaf samples (0.5 g) were finely homogenized in phosphate buffer (50 mM; pH 7.8) in an ice bath. Samples were then centrifuged 12,000× g for 10 min at 4 °C, collected 1 mL supernatant in a clean glass test tube and mixed with 5 mL Bradford reagent. Samples were incubated for 15 min at room temperature and determined protein contents with a spectrophotometer (IRMECO, 2020, Lütjensee, Germany) at 595 nm.

2.5. Determination of Antioxidant Enzymes Activities

Enzyme extract was collected by homogenizing fresh leaf samples in 10 mL of phosphate buffer (50 mM; pH 7.8) and centrifuged at 15,000× g for 20 min at 4 °C.
Giannopolitis and Ries [38] method was used to appraise the activity of SOD via inhibition in photoreduction of nitrobluetetrazolium (NBT). The amount of enzyme that inhibits 50% of NBT is considered equivalent to one unit of SOD activity. Reaction mixture consists of 400 µL of distilled H2O + 250 µL buffer (pH 7.8) + 100 μL methionine + 50 μL NBT + 50 μL leaf extract and 50 µL riboflavin. Plastic cuvettes containing reaction mixture were kept under light for 20 min. and read OD at 560 nm with a spectrophotometer.
For the determination of CAT and POD activities, the Chance and Maehly [39] method was used. The reaction mixture was prepared by adding 50 mM phosphate buffer (1.9 mL) + 5.9 mM H2O2 (1 mL) in 100 µL enzyme extract. Change in CAT activity was determined after every 20 s for 2 min. at 240 nm with spectrophotometer. For POD determination reaction solution contain 750 µL phosphate buffer (50 mM), 100 µL guaiacol (20 mM), 100 μL H2O2 (40 mM) and 100 μL enzyme extract. For 3 min. absorbance of reaction mixture was read after every 20 s at 470 nm with spectrophotometer.

2.6. Determination of Free Proline Contents

Fresh leaf samples (0.5 g) were finely homogenized in 10 mL of 3% sulfosalicylic acid (0.14 M), centrifuged 15,000× g for 20 min. The 2 mL supernatant was mixed with 2 mL acid ninhydrin (pH 3.6) and 2 mL glacial acetic acid (pH 2.4) and incubated at 95 °C for 60 min. Next cooled the samples immediately, added 4 mL of toluene, vortexed and read absorbance of chromophore layer 520 nm with spectrophotometer according to the method of Bates [40].

2.7. Mineral Ions Determination

Shoot and root mineral contents were determined according to the method of Allen [41]. To 0.1 g finely grinded shoot or root material were separately digested in concentrated sulfuric acid in 50 mL digestion flasks and incubated overnight at room temperature. Samples were then placed on a hot plate, the temperature gradually increased to 250 °C until fumes started liberating. Then 0.5 mL of H2O2 (35%) was added in the containing flasks until samples became colorless. Cooled the samples, increased volume up to 50 mL with distilled H2O and filtered. Filtrate was then used for the determination of various ions such as Na+, K+ and Ca2+ with the help of a flame photometer from the Jenway (PEP 7) company (Vernon Hills, IL, USA).

2.8. Statistical Analysis of Data

Data of various growth and physiochemical parameters were analyzed using Co-STAT computer program for analysis of variance (ANOVA) determination. For comparing mean values least significant difference was used according to the method of Snedecor and Cochran [42].

3. Results

3.1. Effect of Salinity Stress and Proline on Growth and Yield Attributes of Pea Seedlings

Shoot fresh/dry weight, shoot length and root length were reduced significantly (p ≤ 0.001) under salinity stress compared to control plants (Table 1). On the other hand, all studied morphological features tended to enhance with foliar application of Pro (Figure 1). Both pea cultivars showed non-significant difference (p ≤ 0.05) with respect to saline and proline treatment, except for shoot dry weight (Figure 1b) and shoot length (Figure 1e, Table 1). Salinity stress decreased the shoot fresh and dry weight by 13.5% and 37.7%, and root fresh and dry by 5.72% and 10.7%, respectively, compared to the control (Figure 1a–d). Similarly, shoot length and root length showed 12% and 2.3% decline under salt stress, respectively (Figure 1e,f). The foliar application of Pro displayed stimulatory effects on growth parameters to mitigate the saline toxicity. The foliar spray of 20 mM Pro increased the shoot fresh and dry weight by 10.7% and 13.5%, root fresh and dry weight 26.9% and 8.8%, and shoot length by 1.64% under salinity stress, respectively. Moreover, 20 mM Pro treatment more significantly increased growth attributes under salinity stress as well as control condition (Figure 1). For a few growth attributes, cv. Round of pea plant showed more improvements compared to L-888 with foliar application of Pro with and without stress (Figure 1).
Yield attributes, number of pods plant−1 (Figure 2a), pod fresh weight (Figure 2b), pods fresh weight plant−1 (Figure 2c), number of seeds pod−1 (Figure 2d), and number of seeds plant−1 (Figure 2e) significantly (p ≤ 0.001) decreased under salt stress (Table 1). The number of pods plant−1, pods fresh weight plant−1, and number of seeds plant decreased by 2.18-fold (Figure 2a), 3.49-fold (Figure 2b) and 3.96-fold (Figure 2c), and number seeds pod−1 by 12.89% (Figure 2d) and 93.7% (Figure 2e), respectively, compared to the control (Figure 2). Similarly, the effect of proline application was on all studied yield attributes under salt stress; however, it enhanced significantly under non-stress conditions, particularly at 10 Mm concentration (Figure 2). Both cultivars showed significant (≤0.01) difference for pod weight plant−1, number of seeds pod−1 and number of seeds plant−1, as cv. Round was higher in these measured yield attributes than those of cv. L-888. Foliar application of different proline levels slightly increased the yield attributes (Table 1).

3.2. Effect of Salinity Stress and Proline on Gas Exchange Characteristics of Pea Seedlings

Net CO2 assimilation rate (A), transpiration rate (E), water use efficiency (WUE), and stomatal conductance (gs) significantly (p ≤ 0.001) decreased, while sub-stomatal CO2 (Ci) increased in both pea cultivars under salt stress (Table 1). Salinity stress decreased the A, E, and gs by 10.29, 9.67, and 8.16%, respectively (Figure 3a,b,d), while Ci increased marginally 2.69% and WUE remain unaltered compared to control (Figure 3c,e). The foliar application of Pro displayed negative impact on WUE by decreasing its efficiency compared to salt stress with Pro treatment (Figure 3c). A considerable variation had been observed in both pea cultivars as cv. Round was higher in gas exchange attributes than those of cv. L-888, except subcellular CO2 concentration (Ci) that was high in cv. L-888. Of the varying proline levels, 20 mM showed more stimulating effect on gas exchange characteristics.

3.3. Effect of Salinity Stress and Proline on Chlorophyll Fluorescence Attributes of Pea Seedlings

Photosynthetic efficiency might be a determinant factor in identifying the salt stress in both pea cultivars. Maximum quantum yield of photosystem II (Fv/Fm) (Figure 3f) and photochemical quenching (qP) (Figure 4a) did not alter either by salt stress or foliar application of various Pro levels (Table 1). However, the coefficient of non-photochemical quenching (qN) (Figure 4c) and non-photochemical quenching (NPQ) (Figure 4d) significantly increased by 28.57% and 31.24% in L-888 pea cultivars under salt stress. Foliar application of proline showed a uniform behavior for qN, while markedly decreased NPQ values in both pea cultivars (Figure 4). Electron transport rate (ETR) (Figure 4b) significantly decreased under both salt stress and foliar application of different proline levels in only pea cultivar Round (Table 2). Of the two proline levels, both levels of proline showed non-significant differences on both pea cultivars (Figure 4).

3.4. Effect of Salinity Stress and Proline on Total Soluble Proteins, Antioxidant Enzymes and Free Proline Contents of Pea Seedlings

Treatment of Pro under NaCl stress resulted in significantly (p ≤ 0.001) higher leaf concentrations of SOD, CAT and proline (Figure 5) as compared to control plants (Table 2). Total soluble proteins significantly decreased in both pea cultivars under salt stress (Figure 5a). Cultivar Round was higher in soluble proteins as compared to cv. L-888 under saline regimes. Foliar application of proline did not alter free proline contents significantly (Table 2).
Activity of superoxide dismutase (SOD) (Figure 5b) significantly decreased, catalase (CAT) (Figure 5d) increased, while peroxidase (POD) (Figure 5c) remained uniform in both pea cultivars under salt stress. However, exogenous application of 10 mM Pro increased the total soluble protein contents and proline concentration by 10.13%, and 2.3% respectively in cv. L-888. SOD concentration decreased with 20 mM Pro treatment in L-888; however, it increased marginally (2.6%) in cv. Round under salt stress. Of the two pea cultivars, L-888 was higher in SOD activity, while Round excelled L-888 in CAT activity. Foliar application of proline significantly increased POD activity in both pea cultivars, while activities of SOD and CAT were not altered significantly under saline or non-saline conditions (Table 2).
Free proline contents significantly increased under salt stress (Figure 5e). Pea cultivar Round was higher than those of L-888 in accumulation of free proline contents under saline or non-saline conditions (Table 2). Foliar application of proline did not increase the endogenous free proline contents (Table 2).

3.5. Effect of Salinity Stress and Proline on Mineral Contents of Pea Seedlings

Imposition of NaCl salinity significantly (p ≤ 0.001) increased shoot and root Na+1 concentration compared to control plants (Table 2). However, application of Pro tended to reduce the Na+1 toxicity under salinity treatment (Figure 6). Mineral nutrients (Table 2), including potassium and calcium, were significantly (p ≤ 0.001) reduced by NaCl salinity treatment compared to control plants. The Shoot and root Na+1 concentration increased by 4.08-fold (Figure 6a) and 2.37-fold (Figure 6b), while K+1 concentration in shoot and root decreased by 34.16% (Figure 6c,d) and shoot and root Ca2+ concentration by 11.19% (Figure 6e,f) compared to the control (Figure 6). However, the foliar application of Pro significantly enhanced shoot and root mineral nutrients with and without salt stress. Cultivar L-888 showed higher shoot and root Na+ contents than those of cv. Round, while reverse was true for cv. Round in terms of shoot and root K+ and Ca2+ contents (Figure 6). Of three levels of proline, 20 mM was proven to be more effective in decreasing Na+1, while increasing K+1 and Ca2+ concentration in both pea cultivars under saline regimes.

4. Discussion

Osmotic stress, ionic imbalance and oxidative stress are the major salt-induced mechanisms involved in yield reduction of crop plants [43]. Plants respond to abiotic stresses by the synthesis and accumulation of some low molecular weight metabolites that include various types of free amino acids, particularly proline [44]. Proline comprises 5% of the total pool of free amino acids under normal conditions; however, under stressful conditions its concentration may rise up to 80% in many species [45]. Proline is a compatible osmolyte that plays vital role in osmoregulation by lowering the osmotic potential of cells, allowing more entry of water molecules, thus preventing plant tissues from the desiccation effect caused by water shortage from the external environment. Under stressful conditions proline acts as an osmoprotectant [46];, a reactive oxygen species scavenger [27]; a sink for energy for the regulation of oxidation reduction reactions [47]; protector of macromolecules such as proteins, lipids, nucleic acids from denaturation [48]; a source of nitrogen [49]; and regulates activity of ribulose bisphosphate oxygenase carboxylase (Rubisco). However, some investigators also serve proline as an indicator of salt stress rather than a means of salt stress tolerance [50].
Salt-induced growth and yield reduction in current investigation (Figure 1 and Figure 2), might be an outcome of both reduced stomatal conductance and CO2 fixation along with non-stomatal factors such as impaired photosynthetic machinery [51]. A higher accumulation of salt in the soil causes osmotic imbalance in plants that ultimately effects cell expansion in root tips; thus, it reduces root growth, consequently hindering plant growth and yield [52]. In the current study, foliar application of proline (20 mM) mitigated the salt stress effect on most of the growth and yield attributes of both pea cultivars. In accordance with our findings, exogenous application of proline showed effective role in improving growth under salt stress (Figure 1 and Figure 2) as proven in various crop species such as Arabidopsis thaliana [53], tobacco [54], mustard [55], and wheat [56]. Under high-salt conditions, exogenous application of proline significantly enhances plant growth with a marked increase in the seed germination, plant biomass, photosynthesis, gas exchange, and grain yield. Very clearly, these positive stimulatory effects are primarily driven by improved nutrient acquisition, water uptake, and biological nitrogen fixation [57]. Exogenous application of proline may alleviate reduction in growth, shoot lengths, and fresh and dry matter through upregulating stress-protective proteins (i.e., increased synthesis of polypeptides 112 and 48 kDa) under varying levels of salt stress [33].
Low uptake of CO2 ultimately led to a decrease in gas-exchange characteristics, in particular the net CO2 assimilation rate as observed in the current study (Figure 3). However, saline conditions slightly increased sub-stomatal CO2 concentration (Ci). Ionic imbalance and toxic effects of sodium and chloride ions might be another possible reason for reduction in net photosynthetic rate, stomatal conductance, chlorophyll contents and an increase in intracellular CO2 level under salt stress [58,59]. In this study, foliar application of proline significantly increased net photosynthetic rate (A) and stomatal conductance (gs) in both pea cultivars (Figure 3). Proline has been considered effective in reducing oxidative stress and enhancing photosynthetic process under salt stress conditions in mustard [15].
Chlorophyll fluorescence attributes might be served as a nondestructive and noninvasive way to undermine the effects of salt stress on the photosynthetic apparatus [60]. We found that the 150 mM NaCl salt stress regime influenced the chlorophyll fluorescence characteristics of both pea cultivars in comparison to the control (Figure 4). Related to the chlorophyll fluorescence, FV/FM is the most sensitive and significant attribute. Maximum quantum yield (Fv/Fm), photochemical quenching (qP) and electron transport rate (ETR) have been reported to be adversely affected under salt stress [61,62]. In another report, saline stress initially increased the non-photochemical quenching (NPQ), but long-term saline stress decreased it [63]. Hamani [64] suggested that more intensive studies are required to further analyze energy partitioning in response to foliar spraying with osmolytes in salt-stressed plants. Furthermore, some reports also suggested toxic effects of exogenously applied proline when supplied at higher concentrations [26,65]. Similarly in the current experiment, a higher concentration of Pro tends to decrease some attributes like total soluble sugar, SOD, qP, qN, NPQ, Fv/Fm in pea seedlings under salt stress.
Exogenous application of proline could decrease H2O2 contents and increase activities of antioxidant enzymes (POD, CAT and ascorbate peroxidase; APX) under salt stress, though it did not improve growth significantly. In this study, SOD activity decreased, while that of CAT (in both pea cultivars) and POD (in cv. L-888 only) increased under salt stress. The cell suspension culture of a tobacco plant also showed significant reduction of the activities of SOD, CAT and POD under salt stress. The foliar application of Pro alleviated the inhibitory effects in CAT and POD activities but not SOD activity under salt stress [66]. Foliar application of proline significantly increased activity of POD in both pea cultivars under both salt stress conditions. In the current study, total soluble proteins decreased under salt stress, while foliar spray of proline did not modulate protein contents significantly under saline or non-saline regimes (Figure 5). Antioxidant enzymes such as SOD protect crop plants by converting superoxide anion to H2O2, while H2O2 are decomposed by the action of CAT and POD under salt stress [67].
In the current study, proline contents significantly increased under salt stress in both pea cultivars. Proline accumulation may be linked with decreased protein synthesis, proline utilization, or proteins hydrolysis [68]. It has been reported that proline catabolism is decreased under osmotic stress, with the withdrawal of stress oxidized by proline dehydrogenase that also acts as a pyrroline-5-carboxylate reductase (proline synthesizing enzyme) or proline oxidase (proline degrading enzyme) [44].
Under high-salinity stress toxic sodium and chloride ions interfere in the uptake of water and essential nutrients [69] resulting in osmotic stress and dehydration of cells [70,71]. The accumulation of Na+ in plant cells constrains potassium ion (K+) uptake, which is essential for plant growth [52]. Under high salt-level, uptake of K+ and Ca2+ reduced, while that of Na+ increased [72]. Excess Na+ influx disturbs ion homeostasis, which results in abrupt changes in enzyme activities and oxidative stress [73]. An optimum amount of K+ and Ca2+ is essential for the functioning and integrity of cellular membranes [74]. Prevention of Na+ influx and enhancing K+ uptake and/or maintaining K+ homeostasis is involved in salt tolerance in plants [75]. Salt tolerant cultivars maintain a high level of K+ and Ca2+ ions under salt stress [76,77]. Calcium (Ca2+) acts as a signaling molecule and plays important role in maintaining ions homeostasis or osmotic adjustment [9,78]. Osmotic adjustment through accumulation of cheap osmoticum can increase the photosynthetic rate of and afford high-yield production in plants [79]. Among different stressors [80,81,82,83,84,85,86,87,88], salt stress is becoming an alarming factor for plant growth and development [11]. Proline protects photosynthetic machinery through maintaining ionic homeostasis under salt-induced oxidative stress [89]. In this study, foliar application of proline significantly increased shoot and root K+ and Ca2+ contents in both pea cultivars. Cultivar Round showed higher contents of shoot and root K+ and Ca2+ as compared to L-888, while the reverse was true for cultivar L-888 in terms of shoot and root Na+ contents.

5. Conclusions

In conclusion, salt stress of 150 mM NaCl adversely affected growth, gas exchange characteristics, chlorophyll fluorescence, and mineral nutrients in both pea cultivars. Foliar application of varying proline levels significantly increased growth, yield, net photosynthetic rate (A), stomatal conductance (gs), activity of peroxidase, and shoot and root K+ and Ca2+ contents, while decreasing non-photochemical quenching values in both pea cultivars. Of the two pea cultivars, cv. Round showed higher growth, yield, photosynthetic efficiency, soluble proteins, activity of catalase, free proline, and shoot and root K+ and Ca2+ contents as compared to cv. L-888. Irreversible damage at the cellular level and photoinhibition due to the high production of reactive oxygen species (ROS) and less CO2 availability is directly linked with salinity stress. The detrimental role of exogenously applied proline in mitigating the inhibitory effect of salt stress appears to be dose-dependent. It is yet not clear how proline actually works in minimizing the negative effects of salinity in pea plants, and further intensive research is needed. Omics approaches can be very helpful in obtaining more holistic molecular perspective of plants compared to other available traditional approaches. To further our understanding of which exogenous proline improves plant–water relations under salt stress, the effect of this osmoprotectant on the expression of aquaporin genes under salt stress will be interesting to investigate.

Author Contributions

Conceptualization; S.S. and M.S. Data curation; M.S., M.F.M. and U.Z. Formal analysis; T.J. and M.F.A. Investigation; S.S. Methodology; F.F. and T.J. Project administration; M.S. Resources; M.S. Software; F.F. Supervision; M.S. Validation; M.S. Writing—original draft; S.S. Writing—review & editing; S.S., M.S., F.F., T.J., M.F.A., M.A., A.S.A., M.F.M. and U.Z. All authors have read and agreed to the published version of the manuscript.

Funding

The authors thank Taif University Researchers Supporting project number (TURSP 2020/257), Taif University, Saudi Arabia for financially supporting the current research.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to acknowledge Taif University Researchers Supporting project number (TURSP 2020/257), Taif University, Saudi Arabia.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

Anet CO2 assimilation rate
Etranspiration rate
gsstomatal conductance
Cisub-stomatal CO2 concentration
qNcoefficient of non-photochemical quenching
NPQnon-photochemical quenching
SODsuperoxide dismutase
CATcatalase
PODperoxidase
ROSreactive oxygen species
MDAmalondialdehyde
WUEwater use efficiency
(Fv/Fm)maximum quantum yield of photosystem II
ETRelectron transport rate

References

  1. Gad, A. Qualitative and quantitative assessment of land degradation and desertification in Egypt based on satellite remote sensing: Urbanization, salinization and wind erosion. In Environmental Remote Sensing in Egypt; Springer: Berlin/Heidelberg, Germany, 2020; pp. 443–497. [Google Scholar]
  2. Hayat, K.; Bundschuh, J.; Jan, F.; Menhas, S.; Hayat, S.; Haq, F.; Shah, M.A.; Chaudhary, H.J.; Ullah, A.; Zhang, D. Combating Soil Salinity with Combining Saline Agriculture and Phytomanagement with Salt-Accumulating Plants. Crit. Rev. Environ. Sci. Technol. 2020, 50, 1085–1115. [Google Scholar] [CrossRef]
  3. Gopalakrishnan, T.; Kumar, L. Modeling and Mapping of Soil Salinity and Its Impact on Paddy Lands in Jaffna Peninsula, Sri Lanka. Sustainability 2020, 12, 8317. [Google Scholar] [CrossRef]
  4. Safdar, H.; Amin, A.; Shafiq, Y.; Ali, A.; Yasin, R.; Shoukat, A.; Hussan, M.U.; Sarwar, M.I. A Review: Impact of Salinity on Plant Growth. Nat. Sci. 2019, 17, 34–40. [Google Scholar]
  5. Rengasamy, P. World Salinization with Emphasis on Australia. J. Exp. Bot. 2006, 57, 1017–1023. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  6. Ali, Q.; Ahmar, S.; Sohail, M.A.; Kamran, M.; Ali, M.; Saleem, M.H.; Rizwan, M.; Ahmed, A.M.; Mora-Poblete, F.; do Amaral Júnior, A.T. Research Advances and Applications of Biosensing Technology for the Diagnosis of Pathogens in Sustainable Agriculture. Environ. Sci. Pollut. Res. 2021, 28, 9002–9019. [Google Scholar] [CrossRef] [PubMed]
  7. Deng, G.; Yang, M.; Saleem, M.H.; Rehman, M.; Fahad, S.; Yang, Y.; Elshikh, M.S.; Alkahtani, J.; Ali, S.; Khan, S.M. Nitrogen Fertilizer Ameliorate the Remedial Capacity of Industrial Hemp (Cannabis sativa L.) Grown in Lead Contaminated Soil. J. Plant Nutr. 2021, 44, 1770–1778. [Google Scholar] [CrossRef]
  8. Hashmat, S.; Shahid, M.; Tanwir, K.; Abbas, S.; Ali, Q.; Niazi, N.K.; Akram, M.S.; Saleem, M.H.; Javed, M.T. Elucidating Distinct Oxidative Stress Management, Nutrient Acquisition and Yield Responses of Pisum sativum L. Fertigated with Diluted and Treated Wastewater. Agric. Water Manag. 2021, 247, 106720. [Google Scholar] [CrossRef]
  9. Li, P.; Zhu, Y.; Song, X.; Song, F. Negative Effects of Long-Term Moderate Salinity and Short-Term Drought Stress on the Photosynthetic Performance of Hybrid Pennisetum. Plant Physiol. Biochem. 2020, 155, 93–104. [Google Scholar] [CrossRef]
  10. Nizam, I. Effects of Salinity Stress on Water Uptake, Germination and Early Seedling Growth of Perennial Ryegrass. Afr. J. Biotechnol. 2011, 10, 10418–10424. [Google Scholar]
  11. Liu, L.; Nakamura, Y.; Taliman, N.A.; Sabagh, A.E.L.; Moghaieb, R.E.A.; Saneoka, H. Differences in the Growth and Physiological Responses of the Leaves of Peucedanum Japonicum and Hordeum vulgare Exposed to Salinity. Agriculture 2020, 10, 317. [Google Scholar] [CrossRef]
  12. Fozia, F.; Muhammad, A.; Abdul, W.; Bushra, S. Modulation of Ionic and Water Status by Moringa Oleifera Extract against Cadmium Toxicity in Wheat (Triticum aestivum). Int. J. Agric. Biol. 2018, 20, 2692–2700. [Google Scholar]
  13. Iqbal, A.; Iftikhar, I.I.; Nawaz, H.; Nawaz, M. Role of Proline to Induce Salinity Tolerance in Sunflower (Helianthus annusl). Sci. Technol. Dev. 2014, 33, 88–93. [Google Scholar]
  14. Farhat, F.; Arfan, M.; Wang, X.; Tariq, A.; Kamran, M.; Tabassum, H.N.; Tariq, I.; Mora-Poblete, F.; Iqbal, R.; El-Sabrout, A.M. The Impact of Bio-Stimulants on Cd-Stressed Wheat (Triticum aestivum L.): Insights into Growth, Chlorophyll Fluorescence, Cd Accumulation, and Osmolyte Regulation. Front. Plant Sci. 2022, 13, 850567. [Google Scholar] [CrossRef]
  15. Shafiq, F.; Iqbal, M.; Ashraf, M.A.; Ali, M. Foliar Applied Fullerol Differentially Improves Salt Tolerance in Wheat through Ion Compartmentalization, Osmotic Adjustments and Regulation of Enzymatic Antioxidants. Physiol. Mol. Biol. Plants 2020, 26, 475–487. [Google Scholar] [CrossRef] [PubMed]
  16. Javaid, A.; Ghafoor, A.; Anwar, R. Evaluation of Local and Exotic Pea Pisum sativum Germplasm for Vegetable and Dry Grain Traits. Pak. J. Bot. 2002, 34, 419–427. [Google Scholar]
  17. Sofy, M.R.; Elhindi, K.M.; Farouk, S.; Alotaibi, M.A. Zinc and Paclobutrazol Mediated Regulation of Growth, Upregulating Antioxidant Aptitude and Plant Productivity of Pea Plants under Salinity. Plants 2020, 9, 1197. [Google Scholar] [CrossRef] [PubMed]
  18. Vikash, M.; Singh, V.; George, S.G.; Vishkarma, S.P. Performance of Different Organic Liquid Manures on Growth, Yield and Economics of Field Pea (Pisumsativum L.). Int. J. Plant Soil Sci. 2022, 11, 44–48. [Google Scholar] [CrossRef]
  19. Shaukat, M.; Wu, J.; Fan, M.; Hussain, S.; Yao, J.; Serafim, M.E. Acclimation Improves Salinity Tolerance Capacity of Pea by Modulating Potassium Ions Sequestration. Sci. Hortic. 2019, 254, 193–198. [Google Scholar] [CrossRef]
  20. Nusrat, N.; Shahbaz, M.; Perveen, S. Modulation in Growth, Photosynthetic Efficiency, Activity of Antioxidants and Mineral Ions by Foliar Application of Glycinebetaine on Pea (Pisum sativum L.) under Salt Stress. Acta Physiol. Plant. 2014, 36, 2985–2998. [Google Scholar] [CrossRef]
  21. Ozturk, L.; Demir, Y.; Unlukara, A.; Karatas, I.; Kurunc, A.; Duzdemir, O. Effects of Long-Term Salt Stress on Antioxidant System, Chlorophyll and Proline Contents in Pea Leaves. Rom. Biotechnol. Lett. 2012, 17, 7227–7236. [Google Scholar]
  22. Jamil, M.; Kharal, M.A.; Ahmad, M.; Abbasi, G.H.; Nazli, F.; Hussain, A.; Akhtar, M.F.U.Z. Inducing Salinity Tolerance in Red Pepper (Capsicum annuum L.) through Exogenous Application of Proline and L-Tryptophan. Soil Environ. 2018, 37, 160–168. [Google Scholar] [CrossRef]
  23. Nazia, K.; Khalid, N.; Khalid, H.; Bhatti, K.H.; Siddiqi, E.H.; Aqsa, T. Effect of Exogenous Applications of Glycine Betaine on Growth and Gaseous Exchange Attributes of Two Maize (Zea mays L.) Cultivars under Saline Conditions. World Appl. Sci. J. 2014, 29, 1559–1565. [Google Scholar]
  24. Yildiztugay, E.; Ozfidan-Konakci, C.; Kucukoduk, M.; Duran, Y. Variations in Osmotic Adjustment and Water Relations of Sphaerophysa Kotschyana: Glycine Betaine, Proline and Choline Accumulation in Response to Salinity. Bot. Stud. 2014, 55, 6. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  25. Noreen, S.; Faiz, S.; Akhter, M.S.; Shah, K.H. Influence of Foliar Application of Osmoprotectants to Ameliorate Salt Stress in Sunflower (Helianthus annuus L.). Sarhad J. Agric. 2019, 35, 1316–1325. [Google Scholar] [CrossRef]
  26. Hayat, S.; Hayat, Q.; Alyemeni, M.N.; Wani, A.S.; Pichtel, J.; Ahmad, A. Role of Proline under Changing Environments: A Review. Plant Signal. Behav. 2012, 7, 1456–1466. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  27. Rejeb, K.B.; Abdelly, C.; Savouré, A. How Reactive Oxygen Species and Proline Face Stress Together. Plant Physiol. Biochem. 2014, 80, 278–284. [Google Scholar] [CrossRef] [PubMed]
  28. De la Torre-González, A.; Navarro-León, E.; Blasco, B.; Ruiz, J.M. Nitrogen and Photorespiration Pathways, Salt Stress Genotypic Tolerance Effects in Tomato Plants (Solanum lycopersicum L.). Acta Physiol. Plant. 2020, 42, 2. [Google Scholar] [CrossRef]
  29. Ji, Y.; Yue, L.; Cao, X.; Chen, F.; Li, J.; Zhang, J.; Wang, C.; Wang, Z.; Xing, B. Carbon Dots Promoted Soybean Photosynthesis and Amino Acid Biosynthesis under Drought Stress: Reactive Oxygen Species Scavenging and Nitrogen Metabolism. Sci. Total Environ. 2022, 856, 159125. [Google Scholar] [CrossRef]
  30. Huang, Y.; Bie, Z.; Liu, Z.; Zhen, A.; Wang, W. Protective Role of Proline against Salt Stress Is Partially Related to the Improvement of Water Status and Peroxidase Enzyme Activity in Cucumber. Soil Sci. Plant Nutr. 2009, 55, 698–704. [Google Scholar] [CrossRef] [Green Version]
  31. Deivanai, S.; Xavier, R.; Vinod, V.; Timalata, K.; Lim, O.F. Role of Exogenous Proline in Ameliorating Salt Stress at Early Stage in Two Rice Cultivars. J. Stress Physiol. Biochem. 2011, 7, 157–174. [Google Scholar]
  32. Hasanuzzaman, M.; Alam, M.; Rahman, A.; Hasanuzzaman, M.; Nahar, K.; Fujita, M. Exogenous Proline and Glycine Betaine Mediated Upregulation of Antioxidant Defense and Glyoxalase Systems Provides Better Protection against Salt-Induced Oxidative Stress in Two Rice (Oryza sativa L.) Varieties. Biomed Res. Int. 2014, 2014, 757219. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  33. Ismail, M.A. Exogenous Proline Induced Changes in SDS-PAGE Protein Profile for Salt Tolerance in Wheat (Triticum aestivum L.) Seedlings. Res. J. Pharm. Biol. Chem. Sci. 2014, 5, 748–755. [Google Scholar]
  34. Bandehagh, A.; Valizadeh, M.; Ghaffari, M.; Jahangir, F.; Dehganian, Z. Pattern of Antioxidant Enzyme Activities under Drought Stress and Exogenous Application of Proline in Sunflower. J. Crop Prod. 2019, 12, 21–34. [Google Scholar]
  35. Perveen, S.; Shahbaz, M.; Ashraf, M. Influence of Foliar-Applied Triacontanol on Growth, Gas Exchange Characteristics, and Chlorophyll Fluorescence at Different Growth Stages in Wheat under Saline Conditions. Photosynthetica 2013, 51, 541–551. [Google Scholar] [CrossRef]
  36. Strasserf, R.J.; Srivastava, A. Polyphasic Chlorophyll a Fluorescence Transient in Plants and Cyanobacteria. Photochem. Photobiol. 1995, 61, 32–42. [Google Scholar] [CrossRef]
  37. Bradford, M.M. A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding. Anal. Biochem. 1976, 72, 248–254. [Google Scholar] [CrossRef]
  38. Giannopolitis, C.N.; Ries, S.K. Superoxide Dismutases: I. Occurrence in Higher Plants. Plant Physiol. 1977, 59, 309–314. [Google Scholar] [CrossRef]
  39. Chance, B.; Maely, A.C. Assay of Catalase and Peroxidase Methods. Enzymology 1955, 2, 755–784. [Google Scholar]
  40. Bates, L.S.; Waldren, R.P.; Teare, I.D. Rapid Determination of Free Proline for Water-Stress Studies. Plant Soil 1973, 39, 205–207. [Google Scholar] [CrossRef]
  41. Allen, S.G.; Dobrenz, A.K.; Schonhorst, M.H.; Stoner, J.E. Heritability of NaCl Tolerance in Germinating Alfalfa Seeds. Agron. J. 1985, 77, 99–101. [Google Scholar] [CrossRef]
  42. Snedecor, G.W.; Cochran, W.G. Statistical Methods, 8thEdn. Ames Iowa State Univ. Press Iowa 1989, 54, 71–82. [Google Scholar]
  43. Siddiqui, M.N.; Mostofa, M.G.; Akter, M.M.; Srivastava, A.K.; Sayed, M.A.; Hasan, M.S.; Tran, L.-S.P. Impact of Salt-Induced Toxicity on Growth and Yield-Potential of Local Wheat Cultivars: Oxidative Stress and Ion Toxicity Are among the Major Determinants of Salt-Tolerant Capacity. Chemosphere 2017, 187, 385–394. [Google Scholar] [CrossRef] [PubMed]
  44. Joseph, E.A.; Radhakrishnan, V.V.; Mohanan, K.V. A Study on the Accumulation of Proline-an Osmoprotectant Amino Acid under Salt Stress in Some Native Rice Cultivars of North Kerala, India. Univ. J. Agric. Res. 2015, 3, 15–22. [Google Scholar] [CrossRef]
  45. Hosseinifard, M.; Stefaniak, S.; Ghorbani Javid, M.; Soltani, E.; Wojtyla, Ł.; Garnczarska, M. Contribution of Exogenous Proline to Abiotic Stresses Tolerance in Plants: A Review. Int. J. Mol. Sci. 2022, 23, 5186. [Google Scholar] [CrossRef] [PubMed]
  46. Al-Huqail, A.; El-Dakak, R.M.; Sanad, M.N.; Badr, R.H.; Ibrahim, M.M.; Soliman, D.; Khan, F. Effects of Climate Temperature and Water Stress on Plant Growth and Accumulation of Antioxidant Compounds in Sweet Basil (Ocimum basilicum L.) Leafy Vegetable. Science 2020, 2020, 3808909. [Google Scholar] [CrossRef] [Green Version]
  47. Miyake, C. Molecular Mechanism of Oxidation of P700 and Suppression of ROS Production in Photosystem I in Response to Electron-Sink Limitations in C3 Plants. Antioxidants 2020, 9, 230. [Google Scholar] [CrossRef] [Green Version]
  48. Ozden, M.; Demirel, U.; Kahraman, A. Effects of Proline on Antioxidant System in Leaves of Grapevine (Vitis vinifera L.) Exposed to Oxidative Stress by H2O2. Sci. Hortic. 2009, 119, 163–168. [Google Scholar] [CrossRef]
  49. Ghosh, U.K.; Islam, M.N.; Siddiqui, M.N.; Cao, X.; Khan, M.A.R. Proline, a Multifaceted Signalling Molecule in Plant Responses to Abiotic Stress: Understanding the Physiological Mechanisms. Plant Biol. 2022, 24, 227–239. [Google Scholar] [CrossRef]
  50. Boulahia, K.; Eid, M.A.M.; Rady, M.M.; Djebbar, R.; Abrous-Belbachir, O. Exogenously Used Proline Offers Potent Antioxidative and Osmoprotective Strategies to Re-Balance Growth and Physio-Biochemical Attributes in Herbicide-Stressed Trigonella Foenum-Graecum. J. Soil Sci. Plant Nutr. 2021, 21, 3254–3268. [Google Scholar]
  51. Flexas, J.; Bota, J.; Loreto, F.; Cornic, G.; Sharkey, T.D. Diffusive and Metabolic Limitations to Photosynthesis under Drought and Salinity in C3 Plants. Plant Biol. 2004, 6, 269–279. [Google Scholar] [CrossRef]
  52. Nguyen, H.T.T.; Bhowmik, S.D.; Long, H.; Cheng, Y.; Mundree, S.; Hoang, L.T.M. Rapid Accumulation of Proline Enhances Salinity Tolerance in Australian Wild Rice Oryza australiensis Domin. Plants 2021, 10, 2044. [Google Scholar] [CrossRef] [PubMed]
  53. Ghosh, D.; Sen, S.; Mohapatra, S. Drought-Mitigating Pseudomonas Putida GAP-P45 Modulates Proline Turnover and Oxidative Status in Arabidopsis Thaliana under Water Stress. Ann. Microbiol. 2018, 68, 579–594. [Google Scholar] [CrossRef]
  54. Ghahremani, M.; Ghanati, F.; Bernard, F.; Azad, T.; Gholami, M.; Safari, M. Ornithine-Induced Increase of Proline and Polyamines Contents in Tobacco Cells under Salinity Conditions. Aust. J. Crop Sci. 2014, 8, 91–96. [Google Scholar]
  55. Iqbal, N.; Umar, S.; Khan, N.A. Photosynthetic Differences in Mustard Genotypes under Salinity Stress: Significance of Proline Metabolism. Annu. Res. Rev. Biol. 2014, 21, 3274–3296. [Google Scholar] [CrossRef]
  56. Noreen, S.; Akhter, M.S.; Yaamin, T.; Arfan, M. The Ameliorative Effects of Exogenously Applied Proline on Physiological and Biochemical Parameters of Wheat (Triticum aestivum L.) Crop under Copper Stress Condition. J. Plant Interact. 2018, 13, 221–230. [Google Scholar] [CrossRef] [Green Version]
  57. El Moukhtari, A.; Cabassa-Hourton, C.; Farissi, M.; Savouré, A. How Does Proline Treatment Promote Salt Stress Tolerance During Crop Plant Development? Front. Plant Sci. 2020, 11, 1127. [Google Scholar] [CrossRef]
  58. Qin, J.; Dong, W.Y.; He, K.N.; Yu, Y.; Tan, G.D.; Han, L.; Dong, M.; Zhang, Y.Y.; Zhang, D.; Li, A.Z. NaCl Salinity-Induced Changes in Water Status, Ion Contents and Photosynthetic Properties of Shepherdia argentea (Pursh) Nutt. Seedlings. Plant Soil Environ. 2010, 56, 325–332. [Google Scholar] [CrossRef] [Green Version]
  59. Tavakkoli, E.; Fatehi, F.; Coventry, S.; Rengasamy, P.; McDonald, G.K. Additive Effects of Na+ and Cl–Ions on Barley Growth under Salinity Stress. J. Exp. Bot. 2011, 62, 2189–2203. [Google Scholar] [CrossRef] [Green Version]
  60. Shahbaz, M.; Ashraf, M.; Athar, H.-R. Does Exogenous Application of 24-Epibrassinolide Ameliorate Salt Induced Growth Inhibition in Wheat (Triticum aestivum L.)? Plant Growth Regul. 2008, 55, 51–64. [Google Scholar] [CrossRef]
  61. Abbas, S.R.; Ahmad, S.D.; Sabir, S.M.; Shah, A.H. Detection of Drought Tolerant Sugarcane Genotypes (Saccharum officinarum) Using Lipid Peroxidation, Antioxidant Activity, Glycine-Betaine and Proline Contents. J. Soil Sci. Plant Nutr. 2014, 14, 233–243. [Google Scholar] [CrossRef] [Green Version]
  62. Perveen, S.; Shahbaz, M.; Ashraf, M. Regulation in Gas Exchange and Quantum Yield of Photosystem II (PSII) in Salt-Stressed and Non-Stressed Wheat Plants Raised from Seed Treated with Triacontanol. Pak. J. Bot. 2010, 42, 3073–3081. [Google Scholar]
  63. Liang, Y.; Sun, M.; Tian, C.; Cao, C.; Li, Z. Effects of Salinity Stress on the Growth and Chlorophyll Fluorescence of Phaeodactylum tricornutum and Chaetoceros gracilis (Bacillariophyceae). Bot. Mar. 2014, 57, 469–476. [Google Scholar] [CrossRef]
  64. Hamani, A.K.M.; Wang, G.; Soothar, M.K.; Shen, X.; Gao, Y.; Qiu, R.; Mehmood, F. Responses of Leaf Gas Exchange Attributes, Photosynthetic Pigments and Antioxidant Enzymes in NaCl-Stressed Cotton (Gossypium hirsutum L.) Seedlings to Exogenous Glycine Betaine and Salicylic Acid. BMC Plant Biol. 2020, 20, 434. [Google Scholar] [CrossRef] [PubMed]
  65. Singhal, R.K.; Fahad, S.; Kumar, P.; Choyal, P.; Javed, T.; Jinger, D.; Singh, P.; Saha, D.; Bose, B.; Akash, H.; et al. Beneficial elements: New Players in improving nutrient use efficiency and abiotic stress tolerance. Plant Growth Regul. 2022, 1–29. [Google Scholar] [CrossRef]
  66. Anamul Hoque, M.; Okuma, E.; Nasrin Akhter Banu, M.; Nakamura, Y.; Shimoishi, Y.; Murata, Y. Exogenous Proline Mitigates the Detrimental Effects of Salt Stress More than Exogenous Betaine by Increasing Antioxidant Enzyme Activities. J. Plant Physiol. 2007, 164, 553–561. [Google Scholar] [CrossRef]
  67. Frary, A.; Göl, D.; Keleş, D.; Ökmen, B.; Pinar, H.; Şiǧva, H.T.; Yemenicioǧlu, A.; Doǧanlar, S. Salt Tolerance in Solanum pennellii: Antioxidant Response and Related QTL. BMC Plant Biol. 2010, 10, 58. [Google Scholar] [CrossRef] [Green Version]
  68. Zhu, B.; Su, J.; Chang, M.; Verma, D.P.S.; Fan, Y.-L.; Wu, R. Overexpression of a Δ1-Pyrroline-5-Carboxylate Synthetase Gene and Analysis of Tolerance to Water-and Salt-Stress in Transgenic Rice. Plant Sci. 1998, 139, 41–48. [Google Scholar] [CrossRef]
  69. Carpici, E.B.; Celik, N.; Bayram, G. The Effects of Salt Stress on the Growth, Biochemical Parameter and Mineral Element Content of Some Maize (Zea mays L.) Cultivars. Afr. J. Biotechnol. 2010, 9, 6937–6942. [Google Scholar]
  70. Tariq, A.; Javaid, A.; Farhat, F.; Aslam, M.M.; Subhani, M.M.; Raja, S.; Naheed, R.; Tabbasum, H.N.; Zulfiqar, S. Proteomic and genomic approaches for antioxidant enzyme-mediated defense analyses in higher plants. In Antioxidant Defense in Plants; Springer: Berlin/Heidelberg, Germany, 2022; pp. 57–70. [Google Scholar]
  71. Maqsood, M.F.; Shahbaz, M.; Arfan, M.; Basra, S.; Ahmed, M. Presowing Seed Treatment with Glycine Betaine Confers NaCl Tolerance in Quinoa By modulating Some Physiological Processes and Antioxidant Machinery. Turk. J. Bot. 2021, 45, 1–14. [Google Scholar] [CrossRef]
  72. Sultana, A.; Mia, M.A.B.; Ahmed, J.U. Cation Dynamics and Growth Morphology of Aromatic Rice under Salt Stress. Bangladesh J. Sci. Ind. Res. 2021, 56, 207–214. [Google Scholar] [CrossRef]
  73. Okhovatian-Ardakani, A.R.; Mehrabanian, M.; Dehghani, F.; Akbarzadeh, A. Salt Tolerance Evaluation and Relative Comparison in Cuttings of Different Omegranate Cultivar. Plant Soil Environ. 2010, 56, 176–185. [Google Scholar] [CrossRef] [Green Version]
  74. Shihab, M.O.; Hamza, J.H. Seed Priming of Sorghum Cultivars by Gibberellic and Salicylic Acids to Improve Seedling Growth under Irrigation with Saline Water. J. Plant Nutr. 2020, 43, 1951–1967. [Google Scholar] [CrossRef]
  75. Teakle, N.L.; Bazihizina, N.; Shabala, S.; Colmer, T.D.; Barrett-Lennard, E.G.; Rodrigo-Moreno, A.; Läuchli, A.E. Differential Tolerance to Combined Salinity and O2 Deficiency in the Halophytic Grasses Puccinellia ciliata and Thinopyrum ponticum: The Importance of K+ Retention in Roots. Environ. Exp. Bot. 2013, 87, 69–78. [Google Scholar] [CrossRef]
  76. Esmaili, E.; Kapourchal, S.A.; Malakouti, M.J.; Homaee, M. Interactive Effect of Salinity and Two Nitrogen Fertilizers on Growth and Composition of Sorghum. Plant Soil Environ. 2008, 54, 537–546. [Google Scholar] [CrossRef] [Green Version]
  77. Afzal, I.; Rauf, S.; Basra, S.M.A.; Murtaza, G. Halopriming Improves Vigor, Metabolism of Reserves and Ionic Contents in Wheat Seedlings under Salt Stress. Plant Soil Environ. 2008, 54, 382–388. [Google Scholar] [CrossRef] [Green Version]
  78. Shabbir, R.; Javed, T.; Hussain, S.; Ahmar, S.; Naz, M.; Zafar, H.; Pandey, S.; Chauhan, J.; Siddiqui, M.H.; Pinghua, C. Calcium homeostasis and potential roles to combat environmental stresses in plants. South Afr. J. Bot. 2022, 148, 683–693. [Google Scholar] [CrossRef]
  79. Abideen, Z.; Koyro, H.-W.; Huchzermeyer, B.; Ahmed, M.Z.; Gul, B.; Khan, M.A. Moderate Salinity Stimulates Growth and Photosynthesis of Phragmites Karka by Water Relations and Tissue Specific Ion Regulation. Environ. Exp. Bot. 2014, 105, 70–76. [Google Scholar] [CrossRef]
  80. Javed, T.; Shabbir, R.; Ali, A.; Afzal, I.; Zaheer, U.; Gao, S.J. Transcription factors in plant stress responses: Challenges and potential for sugarcane improvement. Plants 2020, 9, 491. [Google Scholar] [CrossRef]
  81. Javed, T.; Afzal, I.; Mauro, R.P. Seed coating in direct seeded rice: An innovative and sustainable approach to enhance grain yield and weed management under submerged conditions. Sustainability 2021, 13, 2190. [Google Scholar] [CrossRef]
  82. Javed, T.; Ali, M.M.; Shabbir, R.; Anwar, R.; Afzal, I.; Mauro, R.P. Alleviation of copper-induced stress in pea (Pisum sativum L.) through foliar application of gibberellic acid. Biology 2021, 10, 120. [Google Scholar] [CrossRef]
  83. Ali, A.; Chu, N.; Ma, P.; Javed, T.; Zaheer, U.; Huang, M.T.; Fu, H.Y.; Gao, S.J. Genome-wide analysis of mitogen-activated protein (MAP) kinase gene family expression in response to biotic and abiotic stresses in sugarcane. Physiol. Plant. 2021, 171, 86–107. [Google Scholar] [CrossRef] [PubMed]
  84. Akhtar, G.; Faried, H.N.; Razzaq, K.; Ullah, S.; Wattoo, F.M.; Shehzad, M.A.; Sajjad, Y.; Ahsan, M.; Javed, T.; Dessoky, E.S.; et al. Chitosan-Induced Physiological and Biochemical Regulations Confer Drought Tolerance in Pot Marigold (Calendula officinalis L.). Agronomy 2022, 12, 474. [Google Scholar] [CrossRef]
  85. Javed, T.; Zhou, J.R.; Li, J.; Hu, Z.T.; Wang, Q.N.; Gao, S.J. Identification and expression profiling of WRKY family genes in sugarcane in response to bacterial pathogen infection and nitrogen implantation dosage. Front. Plant Sci. 2022, 13, 917953. [Google Scholar] [CrossRef] [PubMed]
  86. Javad, S.; Shah, A.A.; Ramzan, M.; Sardar, R.; Javed, T.; Al-Huqail, A.A.; Ali, H.M.; Chaudhry, O.; Yasin, N.A.; Ahmed, S.; et al. Hydrogen sulphide alleviates cadmium stress in Trigonella foenum-graecum by modulating antioxidant enzymes and polyamine content. Plant Biol. 2022, 24, 618–626. [Google Scholar] [CrossRef]
  87. Islam, M.R.; Sarker, B.C.; Alam, M.A.; Javed, T.; Alam, M.J.; Zaman, M.S.U.; Azam, M.G.; Shabbir, R.; Raza, A.; Habib-ur-Rahman, M.; et al. Yield Stability and Genotype Environment Interaction of Water Deficit Stress Tolerant Mung Bean (Vigna radiata L. Wilczak) Genotypes of Bangladesh. Agronomy 2021, 11, 2136. [Google Scholar] [CrossRef]
  88. Hong, D.K.; Talha, J.; Yao, Y.; Zou, Z.Y.; Fu, H.Y.; Gao, S.J.; Xie, Y. Silicon enhancement for endorsement of Xanthomonas albilineans infection in sugarcane. Ecotoxicol. Environ. Saf. 2021, 220, 112380. [Google Scholar] [CrossRef]
  89. Long, M.; Shou, J.; Wang, J.; Hu, W.; Hannan, F.; Mwamba, T.M.; Farooq, M.A.; Zhou, W.; Islam, F. Ursolic Acid Limits Salt-Induced Oxidative Damage by Interfering with Nitric Oxide Production and Oxidative Defense Machinery in Rice. Front. Plant Sci. 2020, 11, 697. [Google Scholar] [CrossRef]
Sustainability 14 13579 g001 550
Figure 1. Changes in the shoot fresh weight (a), shoot dry weight (b), root fresh weight (c), root dry weight (d), shoot length (e), and root length (f) of the 70 days old seedlings of two pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 1. Changes in the shoot fresh weight (a), shoot dry weight (b), root fresh weight (c), root dry weight (d), shoot length (e), and root length (f) of the 70 days old seedlings of two pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g001
Sustainability 14 13579 g002 550
Figure 2. Changes in the yield attributes, number of pods plant−1 (a), pod fresh weight plant−1 (b), pod weight plant−1 (c), number of seeds pod−1 (d), number of seeds plant−1 (e) harvested at 90 days after sowing of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 2. Changes in the yield attributes, number of pods plant−1 (a), pod fresh weight plant−1 (b), pod weight plant−1 (c), number of seeds pod−1 (d), number of seeds plant−1 (e) harvested at 90 days after sowing of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g002
Sustainability 14 13579 g003 550
Figure 3. Changes of the net photosynthetic rate; A (a), transpiration rate; E (b), water-use efficiency; WUE (c), stomatal conductance; gs (d), sub-stomatal CO2 concentration; Ci (e), maximum quantum yield (Fv/Fm) (f) of 70 days old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 3. Changes of the net photosynthetic rate; A (a), transpiration rate; E (b), water-use efficiency; WUE (c), stomatal conductance; gs (d), sub-stomatal CO2 concentration; Ci (e), maximum quantum yield (Fv/Fm) (f) of 70 days old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g003
Sustainability 14 13579 g004 550
Figure 4. Changes of the photochemical quenching; qP (a), electron transfer rate; ETR (b), coefficient of photochemical quenching; qN (c), non-photochemical quenching; NPQ (d) of 70 days-old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 4. Changes of the photochemical quenching; qP (a), electron transfer rate; ETR (b), coefficient of photochemical quenching; qN (c), non-photochemical quenching; NPQ (d) of 70 days-old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g004
Sustainability 14 13579 g005 550
Figure 5. Changes of the total soluble protein (a), superoxide dismutase (b), peroxidase (c), catalase (d) and free proline (e) of 70 days old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 5. Changes of the total soluble protein (a), superoxide dismutase (b), peroxidase (c), catalase (d) and free proline (e) of 70 days old plants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g005
Sustainability 14 13579 g006 550
Figure 6. Changes of the shoot sodium ions; Na+1 (a), root sodium ions; Na+1 (b), shoot potassium ions; K+1 (c), root sodium ions; K+1 (d) shoot calcium ions; Ca+2 (e), and root calcium ions; Ca+2 (f) of 70-day-oldplants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Figure 6. Changes of the shoot sodium ions; Na+1 (a), root sodium ions; Na+1 (b), shoot potassium ions; K+1 (c), root sodium ions; K+1 (d) shoot calcium ions; Ca+2 (e), and root calcium ions; Ca+2 (f) of 70-day-oldplants of both pea cultivars grown under different salt concentration conditions with varying levels of proline foliar application. Values are mean ± SD of three biological replicates. Means sharing a letter for a parameter do not differ significantly at p ≤ 0.05.
Sustainability 14 13579 g006
Table
Table 1. Mean squares from analysis of variance of the data for various growth attributes, gas exchange, and chlorophyll fluorescence of pea (Pisum sativum L.) plants subjected to different concentrations of foliar-applied proline under saline and non-saline conditions.
Table 1. Mean squares from analysis of variance of the data for various growth attributes, gas exchange, and chlorophyll fluorescence of pea (Pisum sativum L.) plants subjected to different concentrations of foliar-applied proline under saline and non-saline conditions.
Source of VariationsdfShoot f. wt.Shoot Dry wt.Root f. wt.Root Dry wt.Shoot Length
Cultivar (Cv)1456.3 ***1.88 ***0.012 *0.008 ***1072.5 ***
Salinity (S)1867 ***2.167 ***0.000ns0.000 ns453.2 ***
Proline (Pro)2142.5 ***0.327 ***0.015 **0.002 ***100.4 ***
Cv × S 123.80 *0.218 ***0.000 ns0.000 ns45.8 *
Cv × Pro25.137 *0.0146 ns0.000 ns0.000 ns3.403 ns
S × Pro211.55 ns0.075 **0.001 ns0.000 ns17.21 ns
Cv × S × Pro218.77 ns0.010 ns0.000 ns0.000 ns1.56 ns
Error366.920.0140.0020.0009.76
Source of VariationdfRoot lengthNumber of pods plant−1Pod f. wt.Pods weight plant−1Number of seeds Pod−1
Cultivar (Cv)125.96 *945.1 ***177.0 ***67571.5 ***33.33 ***
Salinity (S)132.50 **165.0 ***1.74 **3452.2 ***0.333 ns
Proline (Pro)215.50 *1.395 ns0.491 ns270.98 ns1.33 ns
Cv × S 10.88 ns0.520 ns0.062 ns913.01 **3.00 *
Cv × Pro21.628 ns0.812 ns0.274 ns199.5 ns0.583 ns
S × Pro24.718 ns0.395 ns0.266 ns38.18 ns0.083 ns
Cv × S × Pro20.446 ns0.145 ns0.065 ns11.97 ns0.000 ns
Error363.981.5480.18184.490.583
Source of VariationdfNumber of seeds plant−1AEA/E (WUE)gs
Cultivar (Cv)175,366.7 ***14.97 ***0.060 ***118.2 ***1704.0 ***
Salinity (S)110034.0 ***16.20 ***0.143 ***23.03 ns4218.7 ***
Proline (Pro)2298.8 ns1.257 **0.004 ns8.117 ns228.8 **
Cv × S 11474.0 **2.655 **0.000 ns86.04 **140.0 ns
Cv × Pro2154.31 ns0.716 *0.007 ns16.66 ns2.02 ns
S × Pro28.520 ns0.004 ns0.001 ns0.479 ns26.7 ns
Cv × S × Pro215.27 ns0.008 ns0.000 ns1.740 ns14.64 ns
Error36164.40.2100.0038.5740.16
Source of VariationdfCiFv/FmqPqNNPQ
Cultivar (Cv)114714 ***0.023 ns0.001 ns0.018 *0.0216 *
Salinity (S)14320 *0.000 ns0.003 ns0.044 ***0.165 ***
Proline (Pro)22285.9 ns0.023 ns0.009 ns0.0075 ns0.015 *
Cv × S15104.6 *0.03 ns0.033 ns0.005 ns0.187 ***
Cv × Pro2653.2 ns0.001 ns0.008 ns0.0018 ns0.021 *
S × Pro2404.1 ns0.000 ns0.000 ns0.000 ns0.013 *
Cv × S × Pro21425.7 ns0.004 ns0.006 ns0.000 ns0.000 ns
Error36870.50.0080.0100.0030.004
df = degrees of freedom; ***, **, and * significant at 0.001, 0.01, and 0.05 levels, respectively; ns = non-significant. Ci = sub-stomatal CO2 conc.; gs = stomtal conductance; E = transpiration rate; A = net photosynthetic rate; WUE = water use efficiency; Fv/Fm = efficiency of photosystem II; qP = photochemical quenching; qN = co-efficient of non-photochemical quenching; NPQ = non-photochemical quenching.
Table
Table 2. Mean squares from analysis of variance of the data for electron transport rate, total soluble proteins, activities of antioxidant enzymes, free proline, and shoot and root mineral contents of pea (Pisum sativum L.) plants subjected to different concentrations of foliar-applied proline under saline and non-saline conditions.
Table 2. Mean squares from analysis of variance of the data for electron transport rate, total soluble proteins, activities of antioxidant enzymes, free proline, and shoot and root mineral contents of pea (Pisum sativum L.) plants subjected to different concentrations of foliar-applied proline under saline and non-saline conditions.
Source of VariationdfETRTotal Soluble
Proteins		SODCATPOD
Cultivar (Cv)1345.5 ***2.354 *9.458 **1501.4 ***0.561 ns
Salinity (S)16.446 ns3.840 *19.98 *113.0 **0.829 ns
Proline (Pro)27.18 ns1.227 ns1.941 ns11.66 ns2.950 ***
Cv × S 176.48 **0.964 ns1.964 ns70.33 *3.480 **
Cv × Pro28.138 ns1.599 ns1.110 ns46.75 ns1.411 *
S × Pro245.27 **0.132 ns0.887 ns66.33 *0.886 ns
Cv × S × Pro2131.8 ***0.235 ns0.531 ns42.02 ns2.850 **
Error366.9080.5571.09614.770.282
Source of VariationdfProlineShoot Na+Root Na+Shoot K+Root K+
Cultivar (Cv)131.90 ***1104.9 ***645.3 ***78.79 ***338.6 ***
Salinity (S)151.41 ***373.5 ***72.52 **13.54 *103.5 ***
Proline (Pro)21.377 ns5.338 ns7.817 ns9.41 *27.14 ***
Cv × S 11.397 ns540.6 ***188.02 ***0.421 ns10.54 *
Cv × Pro21.502 ns12.9 *6.317 ns0.609 ns13.64 **
S × Pro20.899 ns4.795 ns4.098 ns0.578 ns0.421 ns
Cv × S × Pro20.324 ns0.124 ns17.59 *0.484 ns0.046 ns
Error361.0562.7624.4272.3942.220
Source of VariationdfShoot Ca2+Root Ca2+
Cultivar (Cv)173.75 *80.08 ***
Salinity (S)112.50 *20.02 ***
Proline (Pro)223.26 *10.31 ***
Cv × S 114.63 *0.187 ns
Cv × Pro20.817 ns0.130 ns
S × Pro21.348 ns2.442 ns
Cv × S × Pro20.505 ns0.98 ns
Error362.4010.954
***, **, and * significant at 0.001, 0.01 and 0.05 levels respectively. ns = non-significant; df = degrees of freedom; ETR = electron transport rate.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Shahid, S.; Shahbaz, M.; Maqsood, M.F.; Farhat, F.; Zulfiqar, U.; Javed, T.; Fraz Ali, M.; Alhomrani, M.; Alamri, A.S. Proline-Induced Modifications in Morpho-Physiological, Biochemical and Yield Attributes of Pea (Pisum sativum L.) Cultivars under Salt Stress. Sustainability 2022, 14, 13579. https://doi.org/10.3390/su142013579

AMA Style

Shahid S, Shahbaz M, Maqsood MF, Farhat F, Zulfiqar U, Javed T, Fraz Ali M, Alhomrani M, Alamri AS. Proline-Induced Modifications in Morpho-Physiological, Biochemical and Yield Attributes of Pea (Pisum sativum L.) Cultivars under Salt Stress. Sustainability. 2022; 14(20):13579. https://doi.org/10.3390/su142013579

Chicago/Turabian Style

Shahid, Sadia, Muhammad Shahbaz, Muhammad Faisal Maqsood, Fozia Farhat, Usman Zulfiqar, Talha Javed, Muhammad Fraz Ali, Majid Alhomrani, and Abdulhakeem S. Alamri. 2022. "Proline-Induced Modifications in Morpho-Physiological, Biochemical and Yield Attributes of Pea (Pisum sativum L.) Cultivars under Salt Stress" Sustainability 14, no. 20: 13579. https://doi.org/10.3390/su142013579

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop