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Article

Physiological, Biochemical, Anatomical, and Agronomic Responses of Sesame to Exogenously Applied Polyamines under Different Irrigation Regimes

by
El Sayed M. Desoky
1,
Khadiga Alharbi
2,*,
Mostafa M. Rady
3,
Ahmed S. M. Elnahal
4,
Eman Selem
5,
Safaa M. A. I. Arnaout
1 and
Elsayed Mansour
6,*
1
Botany Department, Faculty of Agriculture, Zagazig University, Zagazig 44519, Egypt
2
Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
3
Botany Department, Faculty of Agriculture, Fayoum University, Fayoum 63514, Egypt
4
Department of Plant Pathology, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt
5
Botany and Microbiology Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt
6
Department of Crop Science, Faculty of Agriculture, Zagazig University, Zagazig 44519, Egypt
*
Authors to whom correspondence should be addressed.
Agronomy 2023, 13(3), 875; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13030875
Submission received: 5 February 2023 / Revised: 9 March 2023 / Accepted: 13 March 2023 / Published: 16 March 2023
(This article belongs to the Special Issue Physiology of Abiotic Stress Tolerance in Crops at Reproductive Stages and Crop Improvement Strategies)
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Abstract

:
Polyamines (PAs) are plant growth regulators that attenuate the destructive impacts of water deficit on sesame plants, particularly in arid regions under abrupt climate change. Limited information is available on the physiological, biochemical, anatomical, and agronomic responses of sesame to exogenous application of PAs under water deficit under field conditions. Thus, a two-season field trial was carried out to assess the impact of exogenously sprayed spermine (Spm), spermidine (Spd), and putrescine (Put) on physio-biochemical and anatomical parameters and their influences on agronomic performance and crop water productivity of sesame plants. The sesame plants were assessed under three irrigation regimes; full irrigation (100% ETc), mild drought (75% ETc), and severe drought (50% ETc) conditions. Drought stress displayed negative impacts on all evaluated parameters. However, exogenously applied Pas, especially Put, restricted the destructive effects of water deficit. The application of PAs exhibited highly significant enhancement in photosynthetic pigments (chlorophyll a, b, and carotenoids), gas exchange (net photosynthetic rate, stomatal conductance, and rate of transpiration), water relations (relative water content, membrane stability index, excised leaf water retention), and plant nutrient content (N, P, and K) compared to untreated plants, particularly under severe drought stress. Moreover, PA application displayed highly significant amelioration in osmoprotectants (free proline, soluble sugars, α-Tocopherol, ascorbate, and glutathione), and antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase). In addition, foliar nourishing with PAs exhibited a highly significant reduction in oxidative stress markers (malondialdehyde, electrolyte leakage, superoxide, and hydrogen peroxide). These positive impacts of PA application under drought stress were reflected in highly significant improvement in anatomical characteristics (midrib length and width, vascular bundle length and width, thickness of phloem, xylem and collenchyma, vessel diameter, and number of xylem rows in midvein bundle), and yield-related traits (plant height, leaf area, number of capsules per plant, 1000-seed weight, seed yield, and oil content). Consequently, exogenous application of PAs (in particular, Put) could be exploited to enhance the crop water productivity and yield traits of sesame plants under low water availability in arid regions.

1. Introduction

Sesame (Sesamum indicum L.) is an essential oilseed crop extensively cultivated for its high-quality nutritional seeds. Its seeds contain high levels of oil, protein, and carbohydrate (13.5%) [1]. Moreover, its seeds have two unique substances: sesamolin and sesamin with a cholesterol-lowering influence in humans [2]. Sesame is considered an alternative cash crop for smallholders with substantial importance in nutritional security, livelihood improvement, and food preservation in developing regions [3].
Food demand is projected to rise substantially due to the fast-growing global population. Accordingly, increasing agricultural production has become crucial to ensure global food security [4]. Simultaneously, field crops suffer from the deleterious effects of global climate change, particularly in arid and semi-arid environments [5,6,7,8]. Precipitation fluctuations and temperature rising are projected to become more frequent and severe. Therefore, water scarcity is expected to be increased, particularly in arid regions [9]. Inducing the plants to drought stress under field conditions restricts turgor and water content, decreases CO2 uptake and photosynthesis activity, reduces transpiration, and limits gaseous exchange [10,11,12]. In addition, water scarcity causes oxidative damage due to increasing the production of reactive oxygen species (ROS) [13]. ROS such as superoxide (O2•−), hydrogen peroxide (H2O2), and hydroxyl OH- radicals impair nucleic acids, inactivate metabolic enzymes, and damage membrane lipids which cause the death of plant cells [14,15]. However, the plants have antioxidant systems comprising non-enzymatic antioxidants (i.e., ascorbic acid, tocopherols, proline, glutathione, etc.) and antioxidant enzymes (i.e., peroxidase, superoxide dismutase, glutathione reductase, catalase, etc.) which alleviate the deleterious impacts of the oxidative stress [16,17]. The oxidative cellular impairment in abiotically stressed plants is adjusted by the capacity of their antioxidant defense systems [18]. Critically, the endogenous antioxidant systems of plants are not sufficient to preserve plant development under environmental stresses. Consequently, stressed plants require exogenous support using antioxidant materials to enhance their tolerance [19,20].
The environmental stresses are complicated, hence, the plant’s reaction to stress is determined by several sensors [21,22,23]. Generally, plants react to abiotic stresses by accumulating a variety of nitrogen-containing molecules, such as quaternary ammonium (glycine betaine), amino acids (proline, arginine), and polyamines (PAs) [24]. PAs, such as Spm, Spd, and Put, are small aliphatic amine compounds [25,26]. These compounds are plant growth regulators that enhance various essential processes in the plants including chromatin structure, DNA synthesis, protein translation, gene transcription, floral development, root elongation, fruit ripening, and leaf senescence [27,28]. Different plant species exposed to abiotic stressors, such as salinity, drought, nutritional deficiencies, low and high temperatures, and others showed substantial changes in PA levels [25]. The three most ubiquitous Pas, Spm, Put, and Spd, occasionally are increased abundantly in response to environmental stresses [29]. Hence, PAs have an integral role in adjusting responses to various abiotic stresses. Accordingly, exogenously sprayed PAs can be exploited to enhance tolerance to a variety of abiotic stressors [3,30]. Previously published reports demonstrated that applied-foliar Put and Spd considerably ameliorated drought tolerance in different crops [31,32]. Consequently, this study aimed at assessing the influence of exogenously applied PAs (i.e., Spm, Spd, Put) on photosynthesis attributes, mineral nutrients, antioxidant system components, anatomical characteristics, agronomic performance, and CWP of sesame plants growing under different drought stress conditions.

2. Materials and Methods

2.1. Experimental Site and Agricultural Treatments

A field experiment was carried out during the two summer growing seasons of 2020 and 2021 at Samakin El-Shark Village, El-Huseneya, Egypt (31° 45′ N, 30° 56′ E). The experimental site is defined by hot dry weather with no rainfall events during the sesame season. The experimental site soil was sandy throughout the profile (91.25% sand, 6.66% silt, and 2.09% clay). In the two growing seasons, the trails were sown during the recommended period of sesame growing in the region, which was mid of April. Before sowing, 75 kg P2O5 per ha as superphosphate (15.5% P2O5) was applied and 115 kg K2O per ha was applied after thinning as potassium sulfate (48% K2O). Nitrogen fertilizer was applied at a rate of 170 kg N/ha as ammonium sulfate (20.5% N) in five splits at 7-day intervals after planting. The other recommended agricultural practices for growing sesame containing drip irrigation and control of weeds, diseases, and pests were performed.

2.2. Plant Material and Irrigation Levels

The used genotype in this study (Giza-32) is a commercial cultivar that is commonly cultivated under Egyptian conditions. Healthy sesame seeds of cultivar Giza-32 were obtained from the Agricultural Research Centre, Egypt. A split plot design was performed in three replications. Irrigation regimes were established in the main plots, while foliar applications were located in sub-plots. Each plot consisted of five 5 m long rows with a 60 cm space between rows and a 20 cm space between hills. Each hill was planted with various seeds and thinned to two seedlings after full emergence after three weeks. The sesame plants were evaluated under three water irrigation levels based on ETc replacement following the crop coefficient approach [33]. During the first and second seasons, the accumulative total irrigation water of the full irrigation regime (100% ETc) was 584 and 607 mm, respectively. The amount of full irrigation decreased by 25% and 50% to provide mild and severe drought stress conditions. During the two seasons, the mild drought regime was 432 and 456 mm, respectively, and the severe drought regime was 294 and 318 mm, respectively. Drought conditions were induced to start from seedling establishment until physiological maturity. A drip irrigation system was used for the experiments. The drip laterals and emitters were separated by 0.6 and 0.30 m, respectively. The emitter flow rate and operating pressure were maintained at 4 L/h and 1 bar, by utilizing a pressure gauge and valve for each irrigation regime.

2.3. Foliar Application

Polyamines, i.e., Spm, Spd, and Put, were obtained from Sigma Aldrich Co., Ltd.). Foliar spray of Spm and Spd at a rate of 1.0 Mm and Put at a rate of 2.0 Mm was carried out according to Liu et al. [34]. The solutions contained 0.01% (v/v) Tween-20 and 0.1% (v/v) ethanol. The same volume of tap water containing the same concentrations of Tween-20 and ethanol was applied as the untreated control. PA foliar spray was added three times during the experiment, 15, 30, and 45 days after sowing.

2.4. Determination of Physio-Chemical Constituents

The physiological measurements were determined 55 days after sowing. The fresh leaves were used to extract photosynthetic pigment content (chlorophyll a, b, and carotenoids) following the methodology of Arnon [35]. Absorbance readings were determined at 480 nm, 645 nm, and 663 nm employing a spectrophotometer (Beckman 640D, USA) to estimate the content of the pigment in mg g−1 leaf fresh weight (FW). Leaf net photosynthetic rate (Pn), rate of transpiration (Tr), and stomatal conductance (gs) were detected for a photosynthetic system utilizing a portable photosynthesis system (LF6400XT, LI-COR- Biosciences, Lincoln, USA), between 9:00 a.m. and 11:00 a.m. Relative water content (RWC) was measured as outlined by Barrs and Weatherley [36]. The fresh weight (FW) of the leaves was recorded, and the leaves were left drenched in water for 3 h. Then, the turgid weight (TW) of the leaves was estimated. The samples were then dried in an oven at 80 °C for 24 h and weighed (DW). The RWC was determined utilizing the following formula: RWC = [(FW − DW)/(TW − DW)] × 100. The method of Premachandra et al. [37] was employed to evaluate the membrane stability index (MSI). The method of Farshadfar et al. [38] was used to estimate excised leaf water retention (ELWR). The membrane stability index (MSI) was estimated utilizing 200 mg of the fresh leaf (two sets) in test tubes containing 10 cm3 of double-distilled water. One group of samples was heated at 40 °C for 30 min. EC was recorded on a conductivity bridge (C1). The second group of samples was boiled at 100 °C for ten minutes in a boiling water bath, and EC was measured (C2). MSI was calculated using the following formula: MSI (%) = (1 − [C1/C2]) × 100. The microkjeldahl method of Chapman and Pratt [39] was used to determine total nitrogen (N). Total phosphorus (P) was estimated colorimetrically utilizing the method of ascorbic acid [40]. Total potassium (K) concentrations were determined using a flame photometer [41]. Malondialdehyde (MDA) was recorded as described by Heath and Packer [42]. MDA content (μmol g−1 FW) was recorded in 0.1 g leaf homogenized in Na-phosphate buffer. The homogenate was centrifuged under cooling at 20,000× g for 25 min. The supernatant was recorded at 532 nm. The total inorganic ions leaked out in the leaves (EL) was determined according to Sullivan [43]. EL was recorded in a solution of 20 leaf disks (0.5 cm) subjected to room temperature, 45 °C–55 °C for 30 min, and 100 °C for 10 min to record ECa, ECb, and ECc respectively. EL was estimated utilizing the formula EL (%) = [(ECb − ECa)/ECc] × 100. The Superoxide (O2•−) content (µmol g−1 FW) in the sesame leaves was estimated as A580 g−1 FW following Kubiś [44]. Hydrogen peroxide (H2O2) was estimated as outlined by Mukherjee and Choudhuri [45]. The method of Bates et al. [46] was applied to record proline accumulation in the sesame leaves. Total soluble sugar content was determined as described by Irigoyen et al. [47]. The method of Ching and Mohamed [48] and Konings et al. [49] was performed to determine α-tocopherol. The content of α-tocopherol was determined by a high-performance liquid chromatography system with a mobile phase (94 mL methanol and 6 mL water) and 1.5 mL/min flow rate at 292 nm of UV detector). Nearly 0.02 g of butylated hydroxyl toluene was added to 0.9 L of extraction solvent (n-hexane-ethyl acetate, n-hexane + 0.1 L of CH3-COO-CH2-CH3). The standard solution and dilutions of 0.02–0.2 mg/mL were prepared utilizing R-TOC (0.05 g/0.1 L n-hexane). The ascorbate (AsA) level was determined as presented by Kampfenkel et al. [50]. The level of reduced glutathione (GSH, μmol per g of leaf FW) was determined as described by Griffith [51].

2.5. Determination of Antioxidants Enzymatic Activities

The enzyme extraction was applied as described by Vitória et al. [52]. Catalase (CAT) was determined spectro-photo-chemically following Chance [53]). The enzyme extract (100 µL) was added to 100 µL of 100 mM H2O2 and the total volume was made up to 1 mL by 250 mM phosphate buffer pH 6.8. The reduction in Optical Density at 240 nm against a blank was recorded every minute. The activity of peroxidase (POX) in the sesame leaves was determined according to Thomas et al. [54]. The enzyme was assayed employing guaiacol as the substrate. The reaction mixture consisted of 3 mL of phosphate buffer (0.1 M, pH 7.0), 30 mL of H2O2 (20 mM), 50 mL of enzyme extract, and 50 mL of guaiacol (20 mM). The reaction mixture was incubated in a cuvette for 10 min at room temperature. The optical density was measured at 436 nm and the enzyme activity was expressed as a value of absorbance units g−1 fresh weight of leaves. Ascorbate peroxidase (APX) was determined spectro-photo-chemically as outlined by Fielding and Hall [55]. The assay was performed at 25 °C in a 1.0 cm light path cuvette and the reaction mixture consisted of 1500 µL pH 7.0 phosphate buffer, 20 µL EDTA, 1000 µL sodium ascorbate, and enzyme extract (20 µL). Superoxide dismutase (SOD) activity was estimated by measuring the reduction in absorbance of the superoxide-nitro blue tetrazolium complex by the enzyme [56]. Glutathione reductase (GR) activity was determined after observing the oxidation of NADPH for three absorbances recorded at 340 nm using a spectrophotometer (Thermo Spectronic, Mercers Row, Cambridge, UK), and the activity was expressed as A564 min/mg/protein [57].

2.6. Anatomical Studies

Fifty-five days after sowing comparative microscopy was performed using the median portion of the main stem leaflet during the second growing season of 2021 [58]. The plant material of the untreated control and the best treatment (Put) under the applied three irrigation regimes were assessed. The preserved leaflets were cut into segments (5 mm long) using double-edge razor blades. The segments were cut into thin cross sections that were then stained with Johansen’s pigments [59], safranin, and fast green. Ethanol and xylene: methyl salicylate (1:2, v/v) was utilized as a clearing solution to clear the samples for fine images. Fine images were acquired using an EVOS FL Cell Imaging System (Thermo Fisher Scientific).

2.7. Agronomic Traits and Crop Water Productivity (CWP)

At physiological maturity, plant height, number of capsules per plant, 1000-seed weight (g), and seed yield (kg ha−1) were recorded. The oil content (%) was determined by applying Soxhlet’s method [60]. Crop water productivity (kg m−3) was calculated as the ratio of seed yield (kg ha−1) to crop evapotranspiration (ET) following Fernández et al. [61].

2.8. Statistical Analysis

R software (version 4.0.2) was used for performing all statistical analyses. The analysis of variance (ANOVA) was applied to explore the differences among the irrigation regimes, foliar applications, and their interactions. The differences among the assessed treatments were separated using the protected Tukey’s HSD test at a significance level of p ≤ 0.05.

3. Results

3.1. Photosynthetic Pigments and Activities

The mild and severe drought regimes displayed gradually declined values of all evaluated photosynthesis attributes compared to the full irrigation regime (Table 1). Appreciably, chlorophyll a, chlorophyll b, carotenoids, gs, Pn, and Tr levels of sesame plants were steeply decreased under severe drought stress. The photosynthesis attributes were significantly reduced by 42.6, 35.8, 5.7, 36.2, 39.7, and 40.8% in the same aforementioned order under severe drought stress conditions compared to non-stressed conditions. However, the application of Spm, Spd, and Put significantly improved all evaluated photosynthesis attributes, especially in the case of Put. Put use stimulated chlorophyll a, chlorophyll b, carotenoids, gs, Pn, and Tr by 47.0, 18.0, 3.2, 27.9, 16.8, and 21.4% compared to untreated control under severe drought stress conditions.

3.2. Cell and Membrane Integrity, Nutrient Content, and Oxidative Stress Markers

The RWC, MSI, and ELWR of leafy tissues and plant nutrient content N, P, and K significantly declined under mild and severe drought compared to full irrigation conditions (Table 2). Reductions in RWC, MSI, ELWR, N, P, and K were more pronounced under severe drought stress. The abovementioned parameters were reduced by 21.1, 34.2, 18.7, 30.0, 37.1, and 36.6%, respectively, under severe drought compared with full irrigation conditions. Notwithstanding, the application of PAs considerably enhanced RWC, MSI, ELWR, N, P, and K under drought stress conditions compared with the untreated control. The application of Put displayed the greatest enhancement. Put ameliorated the abovementioned parameters by 13.3, 27.5, 8.0, 28.9, 22.2, and 27.6%, respectively, compared to untreated control under severe drought stress conditions.
The level of MDA, EL, O2•-, and H2O2 steadily increased with decreasing irrigation regime (Table 3). The highest increment was assigned for severe drought stress compared to non-stressed plants. Severe drought stress increased the oxidative stress markers in the aforementioned order by 171.2, 62.5, 52.3, and 165.9%, respectively, compared to non-stressed plants. Otherwise, the foliar nourishing with PAs exhibited a considerable decrease in MDA, El, O2•-, and H2O2 compared to untreated plants. The application of Put was most functional in mitigating the injurious impacts and reducing the oxidative stress markers. It decreased the abovementioned markers by 32.4, 18.7, 15.0, and 22.4%, respectively, compared to the corresponding controls under severe drought stress conditions.

3.3. Osmoprotectants and Antioxidative Status

The level of free proline, soluble sugars, α-TOC, AsA, GSH, POX, CAT, APX, SOD, and GR considerably elevated under both drought regimes compared to well-watered conditions (Table 4 and Table 5). The increases in all evaluated osmoprotectants and non-enzymatic and enzymatic antioxidants were more pronounced under severe drought than the mild stress conditions. Severe drought stress increased the abovementioned parameters by 36.1, 43.4, 90.1, 121.0, 120.0, 78.3, 46.2, 53.8, 51.9, and 82.8%, respectively, compared to well-watered plants. Moreover, the application of PAs further elevated the antioxidant activities under drought stress compared with the untreated control. Among all applied treatments Put exhibited the best enhancement. The application Put elevated proline, soluble sugars, α TOC, AsA, GSH, POX, CAT, APX, SOD, and GR by 20.6, 31.0, 16.9, 8.5, 8.5, 27.7, 21.1, 8.5, 20.5, 15.9%, respectively, compared to untreated plants under severe drought stress conditions.

3.4. Leaf Anatomy

Drought stress significantly decreased leaf anatomical features; midrib length, midrib width, vascular bundle length, vascular bundle width, phloem tissue thickness, xylem tissue thickness, collenchyma tissue thickness, xylem vessels diameter, and the number of xylem rows in the midvein bundle of the sesame plant (Table 6 and Figure 1). Severe drought stress steeply decreased all the abovementioned anatomical parameters compared to mild drought and well-watered conditions. It considerably decreased the aforementioned characteristics by 57.6, 54.2, 68.7, 59.7, 65.2, 68.3, 60.3, 59.0, and 48.2%, respectively, compared to well-watered plants. However, Put application considerably ameliorated all studied anatomical features by 57.1, 37.3, 9.9, 40.1, 66.7, 60.0, 23.7, 28.9, and 33.3%, respectively, compared to untreated plants under severe drought stress conditions.

3.5. Agronomic Performance and CWP

All evaluated agronomic traits were considerably reduced under mild and severe drought stress compared to the full irrigation regime conditions (Table 7). The reduction in all agronomic traits was more pronounced under severe drought than mild drought conditions. Severe drought stress considerably declined plant height, leaf area, number of capsules per plant, 1000-seed weight, seed yield, and oil content by 34.8, 27.6, 26.6, 18.3, 24.0, and 11.8%, respectively, compared to well-watered treatment. However, the application of PAs significantly boosted all of the aforementioned traits under all tested irrigation regimes compared to untreated control. The application of Put recorded the best enhancement of the abovementioned agronomic traits. It enhanced the agronomic traits by 17.1, 19.2, 10.3, 7.4, 8.8, and 4.1%, respectively, compared to untreated plants under severe drought stress conditions. The sesame plants under mild and severe drought stress conditions displayed higher CWP than under non-stressed conditions (Table 7). The application of PAs substantially enhanced CWP compared with untreated plants with superiority of the application of Put. The treatment of Put exhibited the greatest enhancement and increased CWP by 9.0% compared to untreated plants under severe drought stress conditions.

3.6. Relationships among Evaluated Treatments

Heatmaps are a proper statistical procedure to explore the association among the assessed treatments based on the studied parameters. In the present study, the heatmap and hierarchical clustering based on physiological, biochemical, and agronomic parameters divided the evaluated irrigation regimes (FI, MD, and SD) and applied foliar applications (TW, Spm, Spd, and Put)) into different clusters (Figure 2). The irrigation regimes were the main dividing factor of the main clusters. The full irrigation regimes combined with all applied foliar applications exhibited the highest values for photosynthetic pigments, gas exchange, water relations, plant nutrient content, and agronomic traits (depicted in blue). Otherwise, the abovementioned treatments exhibited the lowest values of oxidative stress markers, osmoprotectants, and antioxidant enzyme activities (depicted in red). Conversely, severe drought stress possessed the lowest values for photosynthetic pigments, gas exchange, water relations, plant nutrient content, and agronomic traits, but the highest values of oxidative stress markers, osmoprotectants, and antioxidant enzyme activities. The mild drought stress conditions displayed intermediate levels of all studied parameters between full irrigation and severe drought stress conditions. In all irrigation regimes, the untreated control had unfavorable values, while Put exhibited favorable values for all studied parameters.

4. Discussion

Drought stress is one of the most restrictive factors for sustainable agriculture [62,63,64]. It devastatingly impacts plant development, growth, and productivity [65,66]. In the present study, reducing irrigation from full irrigation to mild or severe drought stress substantially deactivated the efficiency of photosynthetic machinery (photosynthetic pigments, Pn, gs, and Tr), disturbed leaf tissue integrity (RWC, MSI, and ELWR), unbalanced mineral nutrient contents (N, P, and K), and increased lipid peroxidation (MDA), ionic leakage (EL), and excess oxidants (H2O2 and O2•−). These drought stress-induced effects were accompanied by a significant reduction in anatomical features (midrib length and width, vascular bundle length and width, thickness of phloem, xylem and collenchyma, vessel diameter, and number of xylem rows in the midvein bundle), and agronomic traits (plant height, leaf area, number of capsules per plant, 1000-seed weight, seed yield, and oil content) of the sesame plants. In this context Guidi et al. [67], Rady et al. [68], and Gimenez et al. [69], elucidated that water deficit stimulates chlorophyll degradation and PSII photoinhibition as well as diminished CO2 entry into plant leaves. Likewise, Yokota et al. [70] and Farooq et al. [71] depicted that osmotic stresses reduce transpiration rate, impair net photosynthesis, and disturb nutrient availability, transport, and metabolism.
Under water deficit conditions, the components of the antioxidant (AsA, GSH, α-Toc, POX, SOD, CAT, GR, APX, and osmoprotectants) were markedly raised to enable sesame plants to partially tolerate drought stress impacts. However, the available endogenous antioxidant system is insufficient to attenuate the adverse effects of severe drought and produce acceptable seed yield. Accordingly, the plants need to be supported with antioxidant stimulators to reinforce their tolerance to drought stress and improve their productivity under severe drought stress conditions. Polyamines are intracellular messengers or endogenous plant growth regulators that promote several physiological-biochemical processes in response to drought stress. Hence, they boost tolerance against drought stress and adjust plant development, plant growth, seed yield, and seed quality [72,73]. Although PAs improve the tolerance against various environmental stresses in plants, there is limited information available on their mechanisms in alleviating drought stress adversities [74,75]. Accordingly, in this study, the impacts of foliar-applied PAs (Spm, Spd, and Put) on physiological, biochemical, and anatomical parameters and their influences on agronomic performance and crop water productivity of sesame were assessed under different irrigation regimes. The exogenous application of Spm, Spd, and Put substantially improved photosynthetic attributes (photosynthetic pigments, Pn, gs, Tr), enhanced cell membrane integrity, RWC restoration, mineral nutrient recovery, and upregulation of osmoregulatory compounds (Figure 3). In this context, Minocha et al. [76], Khoshbakht et al. [77], and Nahar et al. [78] disclosed that PA foliar supplementation promotes ionic hemostasis and increases nutrient content under abiotic stress conditions. This may be ascribed to improved root absorption surfaces as a result of a stimulated root system and elevated accumulation of osmoprotectants [74]. Furthermore, Farooq et al. [71], Alcázar et al. [79], and Ahmad et al. [80] reported that PAs mediate the recovery of stressed cells by ameliorating cell turgor (RWC and ELWR) and membrane integrity (MSI) with declined EL, which promotes membrane integrity against oxidative stress. This improvement in RWC, ELWR, and MSI in stressed plants retains cell turgor and wall elasticity [81]. Water relation attributes are associated with net photosynthesis, which allows persistent metabolic activities as effective mechanisms of tolerance to drought stress. This proposes that the preservation of water status through enhancing cellular structure is a decisive mechanism of drought tolerance in stressed plants. Accordingly, PA application enhances the plants to grow better under limited moisture supply conditions.
The protective compounds (e.g., osmoprotectants, non-enzymatic and enzymatic antioxidants) protect the plants from lipid peroxidation (MDA) and ionic leakage (EL) by decreasing the oxidant (H2O2 and O2•−) content [82]. The applied PAs ameliorated the antioxidant defense system by enhancing the synthesis of osmoprotectants and increasing the accumulation of free proline and soluble sugars. Similarly, PAs enhanced the activities of non-enzymatic and enzymatic antioxidants; AsA, GSH, α-Toc, POX, SOD, CAT, GR, and APX. This upregulation and increase in osmotic-protective substances are likely to lead to modulating the production of metabolites involved in stress tolerance. Subsequently, the accumulation pattern of these metabolites revealed robust negative associations with MDA, EL, H2O2, and O2•− [83]. Accordingly, these antioxidants protected sesame plants from oxidative damage and have the potential to act as free radical scavengers [84]. In conclusion, the applied-foliar PAs displayed multiple roles in ameliorating the physiological and biochemical processes of sesame under drought stress. The positive effects of PA application on physio-biochemical parameters were reflected considerably in anatomical characteristics, yield traits, oil content, and crop water productivity. Therefore, the treated plants were better able to withstand drought stress and displayed better performance than untreated ones.

5. Conclusions

The impact of exogenously applied Spm, Spd, and Put on physiological-biochemical and metabolic responses was explored under different irrigation regimes. Exogenous application of Spm, Spd, and Put restored balance to nutrient content, tissue integrity, and photosynthetic efficiency. In addition, it maximized levels of osmoprotectants (soluble sugars and proline), and non-enzymatic and enzymatic antioxidants, which were associated with minimizing oxidants (H2O2, and O2•−) and their damage in terms of ionic leakage (EL) and lipid peroxidation (MDA). These positive impacts result in increased productivity and quality (yield and oil content) of drought-stressed sesame plants compared to untreated plants. Consequently, exogenously applied Spm, Spd, or Put could be considered as an efficient bioactive stimulant to attenuate drought stress damage by elevating osmoprotectant and antioxidant contents, enhancing antioxidative enzyme activities, correcting ionic imbalance, promoting plant growth and production, and, accordingly, reinforcing sustainable sesame production under arid environments.

Author Contributions

Conceptualization, E.S.M.D., M.M.R., A.S.M.E., E.S., S.M.A.I.A. and E.M.; methodology, E.S.M.D., M.M.R., A.S.M.E., E.S. and S.M.A.I.A.; software, E.S.M.D., K.A. and E.M.; validation, E.S.M.D., M.M.R., A.S.M.E., E.S., S.M.A.I.A. and E.M.; formal analysis, E.S.M.D., S.M.A.I.A. and E.M.; investigation, E.S.M.D., M.M.R., A.S.M.E., E.S. and S.M.A.I.A.; resources, K.A. data curation, E.S.M.D. and E.M.; writing—original draft preparation, E.S.M.D., K.A. and E.M.; writing—review and editing, E.S.M.D., K.A. and E.M.; visualization, E.S.M.D. and S.M.A.I.A.; supervision, E.S.M.D. and E.M.; funding acquisition, K.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R188), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Acknowledgments

Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R188), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Conflicts of Interest

The authors declare no conflict of interest.

References

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Figure 1. Transverse section of the terminal leaflet blade of the fourth upper leaf on the main stem of sesame plants affected by irrigation regimes and foliar spray of polyamines during the growing season 2021. (A): under well-watered conditions and sprayed with distilled water, (B): under well-watered conditions and sprayed with putrescine, (C): under moderate drought and sprayed with distilled water, (D): under moderate drought and sprayed with putrescine, (E): under severe drought and sprayed with distilled water, (F): under severe drought and sprayed with putrescine.
Figure 1. Transverse section of the terminal leaflet blade of the fourth upper leaf on the main stem of sesame plants affected by irrigation regimes and foliar spray of polyamines during the growing season 2021. (A): under well-watered conditions and sprayed with distilled water, (B): under well-watered conditions and sprayed with putrescine, (C): under moderate drought and sprayed with distilled water, (D): under moderate drought and sprayed with putrescine, (E): under severe drought and sprayed with distilled water, (F): under severe drought and sprayed with putrescine.
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Figure 2. Heatmap and hierarchical clustering divide the evaluated irrigation regimes and foliar applications into different clusters based on physiological, biochemical, and agronomic traits. Blue and red colors indicate low and high values for the corresponding trait, respectively. FI: full irrigation, MD: mild drought, SD: severe drought, Spm: spermine, Spd: spermidine, and Put: putrescine.
Figure 2. Heatmap and hierarchical clustering divide the evaluated irrigation regimes and foliar applications into different clusters based on physiological, biochemical, and agronomic traits. Blue and red colors indicate low and high values for the corresponding trait, respectively. FI: full irrigation, MD: mild drought, SD: severe drought, Spm: spermine, Spd: spermidine, and Put: putrescine.
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Figure 3. Schematic diagram displaying the mechanisms of polyamines (Spm, Spd, and Put) in mitigating the adverse effects of drought stress on sesame plants. Application of polyamines improved plant growth and yield traits by enhancing (i) non-enzymatic and enzymatic antioxidants; (ii) water relation (iii) nutrient content, (iv) gas exchange, and (v) photosynthetic pigments while reducing oxidative stress markers.
Figure 3. Schematic diagram displaying the mechanisms of polyamines (Spm, Spd, and Put) in mitigating the adverse effects of drought stress on sesame plants. Application of polyamines improved plant growth and yield traits by enhancing (i) non-enzymatic and enzymatic antioxidants; (ii) water relation (iii) nutrient content, (iv) gas exchange, and (v) photosynthetic pigments while reducing oxidative stress markers.
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Table
Table 1. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on photosynthetic pigments and gas exchange of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 1. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on photosynthetic pigments and gas exchange of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorChlorophyll a
(mg g−1 FW)		Chlorophyll b
(mg g−1 FW)		Carotenoids
(mg g−1 FW)		Net Photosynthetic Rate (µmol CO2 m−2 s−1)Transpiration Rate (mmol H2O m−2 s−1)Stomatal Conductance (mmol H2O m−2 s−1)
Irrigation (I)
 FI1.826 ± 0.032 a0.735 ± 0.029 a0.914 ± 0.004 a13.13 ± 0.12 a6.95 ± 0.05 a0.625 ± 0.008 a
 MD1.403 ± 0.036 b0.574 ± 0.033 b0.891 ± 0.005 b10.60 ± 0.17 b5.68 ± 0.10 b0.501 ± 0.011 b
 SD1.048 ± 0.041 c0.472 ± 0.034 c0.862 ± 0.004 c8.38 ± 0.23 c4.19 ± 0.17 c0.370 ± 0.009 c
Foliar (F)
 TW1.25 ± 0.092 d0.546 ± 0.027 d0.878 ± 0.007 d9.94 ± 0.81 d5.27 ± 0.42 d0.458 ± 0.038 d
 Spm1.39 ± 0.081 c0.573 ± 0.025 c0.886 ± 0.004 c10.53 ± 0.69c5.50 ± 0.40 c0.492 ± 0.035 c
 Spd1.51 ± 0.052 b0.605 ± 0.032 b0.890 ± 0.005 b11.03 ± 0.64 b5.71 ± 0.39 b0.510 ± 0.039 b
 Put1.55 ± 0.092 a0.651 ± 0.054 a0.901 ± 0.008 a11.32 ± 0.61 a5.94 ± 0.40 a0.534 ± 0.036 a
Interaction (I × F)
FITW1.68 ± 0.012 c0.662 ± 0.004 d0.902 ± 0.005 d12.8 ± 0.058 d6.74 ± 0.016 d0.586 ± 0.04 d
Spm1.80 ± 0.008 b0.707 ± 0.005 c0.910 ± 0.004 c13.0 ± 0.035 c6.86 ± 0.032 c0.623 ± 0.03 c
Spd1.84 ± 0.011 b0.752 ± 0.004 b0.916 ± 0.006 b13.2 ± 0.029 b6.97 ± 0.035 b0.636 ± 0.04 b
Put1.97 ± 0.009 a0.819 ± 0.007 a0.926 ± 0.003 a13.4 ± 0.035 a7.21 ± 0.041 a0.653 ± 0.04 a
MDTW1.23 ± 0.012 g0.538 ± 0.003 h0.882 ± 0.005 h9.84 ± 0.026 h5.24 ± 0.039 h0.453 ± 0.02 h
Spm1.39 ± 0.009 f0.556 ± 0.002 g0.890 ± 0.004 g10.3 ± 0.045 g5.50 ± 0.032 g0.486 ± 0.02 g
Spd1.44 ± 0.019 e0.586 ± 0.003 f0.893 ± 0.006 f10.9 ± 0.067 f5.81 ± 0.029 f0.516 ± 0.03 f
Put1.55 ± 0.006 d0.617 ± 0.005 e0.898 ± 0.005 e11.3 ± 0.033 e6.15 ± 0.034 e0.564 ± 0.04 e
SDTW0.83 ± 0.002 j0.438 ± 0.002 l0.851 ± 0.007 l7.18 ± 0.028 l3.82 ± 0.011 l0.332 ± 0.01 k
Spm0.98 ± 0.003 i0.456 ± 0.001 k0.857 ± 0.008 k8.25 ± 0.029 k4.13 ± 0.019 k0.366 ± 0.01 j
Spd1.13 ± 0.001 h0.478 ± 0.002 j0.862 ± 0.006 j8.91 ± 0.024 j4.34 ± 0.015 j0.376 ± 0.02 j
Put1.22 ± 0.002 g0.517 ± 0.003 i0.878 ± 0.007 i9.18 ± 0.035 i4.46 ± 0.017 i0.403 ± 0.02 i
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001<0.001
I × F6<0.001<0.001<0.001<0.001<0.0010.004
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 2. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on water relations and nutrient content of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 2. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on water relations and nutrient content of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorRelative Water Content (%)Membrane Stability Index (%)Excised leaf Water Retention (%)Nitrogen (%)Phosphorus (%)Potassium (%)
Irrigation (I)
 FI79.11 ± 0.52 a62.37 ± 0.72 a75.86 ± 0.51 a2.23 ± 0.08 a0.359 ± 0.027 a3.36 ± 0.09 a
 MD72.06 ± 0.61 b54.36 ± 0.87 b66.66 ± 0.52 b1.78 ± 0.14 b0.262 ± 0.021 b2.77 ± 0.05 b
 SD62.38 ± 0.86 c41.04 ± 1.11 c61.66 ± 0.55 c1.56 ± 0.07 c0.226 ± 0.008 c2.13 ± 0.06 c
Foliar (F)
 TW67.89 ± 1.73 d48.62 ± 2.14 d65.43 ± 1.11 d1.53 ± 0.12 d0.220 ± 0.016 d2.54 ± 0.20 c
 Spm71.00 ± 1.36 c52.01 ± 2.16 c67.78 ± 1.08 c1.87 ± 0.09 c0.286 ± 0.017 c2.72 ± 0.17 b
 Spd72.08 ± 1.45 b53.78 ± 2.02 b68.98 ± 1.09 b1.96 ± 0.12 b0.307 ± 0.026 b2.76 ± 0.18 b
 Put73.76 ± 1.28 a55.94 ± 2.20 a70.03 ± 1.06 a2.06 ± 0.19 a0.316 ± 0.043 a3.00 ± 0.19 a
Interaction (I × F)
FITW76.7 ± 0.36 d59.8 ± 0.45 d73.2 ± 0.42 d2.18 ± 0.010 d0.310 ± 0.001 d3.18 ± 0.02 bc
Spm78.6 ± 0.38 c62.1 ± 0.53 c75.6 ± 0.45 c2.30 ± 0.012 c0.350 ± 0.002 c3.22 ± 0.04 bc
Spd79.7 ± 0.42 b63.0 ± 0.52 b76.7 ± 0.49 b2.44 ± 0.013 b0.411 ± 0.003 b3.37 ± 0.06 b
Put81.3 ± 0.45 a64.4 ± 0.57 a77.6 ± 0.53 a2.56 ± 0.014 a0.476 ± 0.002 a3.69 ± 0.02 a
MDTW68.7 ± 0.31 g50.4 ± 0.49 h64.1 ± 0.39 h1.69 ± 0.007 h0.240 ± 0.001 h2.54 ± 0.01 ef
Spm71.9 ± 0.41 f53.5 ± 0.46 g66.2 ± 0.38 g1.78 ± 0.008 g0.254 ± 0.002 g2.72 ± 0.02 de
Spd72.9 ± 0.45 f55.5 ± 0.48 f67.2 ± 0.34 f1.89 ± 0.006 f0.266 ± 0.001 f2.85 ± 0.04 d
Put74.3 ± 0.48 e57.9 ± 0.45 e68.9 ± 0.38 e2.02 ± 0.011 e0.281 ± 0.001 e2.97 ± 0.02 cd
SDTW57.8 ± 0.26 k35.6 ± 0.31 l58.8 ± 0.29 k1.21 ± 0.005 l0.181 ± 0.007 l1.85 ± 0.03 h
Spm62.3 ± 0.28 j40.4 ± 0.32 k61.0 ± 0.32 j1.27 ± 0.004 k0.189 ± 0.003 k2.06 ± 0.04 gh
Spd63.4 ± 0.24 i42.7 ± 0.29 j62.7 ± 0.39 i1.36 ± 0.003 j0.196 ± 0.008 j2.25 ± 0.03 fg
Put65.5 ± 0.32 h45.4 ± 0.28 i63.5 ± 0.38 h1.56 ± 0.002 i0.227 ± 0.001 i2.36 ± 0.02 f
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001<0.001
I × F60.002<0.0010.008<0.0010.006<0.001
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 3. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on oxidative stress markers of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 3. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on oxidative stress markers of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorMalondialdehyde
(µmol g−1 FW)		Electrolyte Leakage (%)Superoxide (A580 g−1 FW)Hydrogen Peroxide
(µmol g−1 FW)
Irrigation (I)
 FI1.84 ± 0.08 c6.83 ± 0.32 c0.65 ± 0.010 c17.00 ± 0.45 c
 MD3.12 ± 0.14 b11.56 ± 0.49 b0.83 ± 0.013 b34.27 ± 1.18 b
 SD4.99 ± 0.24 a11.12 ± 0.26 a0.99 ± 0.018 a45.25 ± 1.56 a
Foliar (F)
 TW4.14 ± 0.51 a10.87 ± 0.84 a0.88 ± 0.055 a37.63 ± 6.38 a
 Spm3.34 ± 0.38 b10.27 ± 0.98 b0.84 ± 0.051 b32.26 ± 5.14 b
 Spd2.86 ± 0.41 c9.43 ± 0.53 c0.80 ± 0.049 c29.53 ± 5.16 c
 Put2.94 ± 0.45 c8.60 ± 0.56 d0.76 ± 0.045 d29.26 ± 5.48 c
Interaction (I × F)
FITW2.25 ± 0.11 h7.93 ± 0.13 i0.69 ± 0.009 h19.3 ± 0.37 g
Spm1.89 ± 0.09 i7.61 ± 0.15 j0.66 ± 0.005 i17.2 ± 0.35 g h
Spd1.62 ± 0.06 j6.56 ± 0.06 k0.63 ± 0.004 j15.8 ± 0.22 h
Put1.59 ± 0.05 j5.21 ± 0.14 l0.60 ± 0.003 j15.7 ± 0.33 h
MDTW3.89 ± 0.08 e10.8 ± 0.14 e0.87 ± 0.007 e40.5 ± 0.26 d
Spm3.13 ± 0.07 f10.4 ± 0.12 f0.85 ± 0.006 e34.5 ± 0.24 e
Spd2.74 ± 0.11 g9.94 ± 0.05 g0.81 ± 0.007 f31.2 ± 0.31 f
Put2.70 ± 0.12 g9.38 ± 0.06 h0.76 ± 0.005 g30.9 ± 0.24 f
SDTW6.26 ± 0.11 a13.9 ± 0.11 a1.07 ± 0.009 a53.1 ± 0.26 a
Spm4.98 ± 0.12 b12.8 ± 0.08 b1.01 ± 0.007 b45.1 ± 0.19 b
Spd4.49 ± 0.10 c11.8 ± 0.09 c0.96 ± 0.006 c41.6 ± 0.18 c
Put4.23 ± 0.11 d11.3 ± 0.07 d0.91 ± 0.007 d41.2 ± 0.27 c
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001
I × F6<0.001<0.0010.0080.002
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 4. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the activities of non-enzymatic antioxidants of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 4. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the activities of non-enzymatic antioxidants of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied Factor Free Proline
(µmol g−1 DW)		 Soluble Sugars
(mg g−1 DW)		α-Tocopherol
(µmol g−1 DW)		Ascorbate
(µmol g−1 FW)		Glutathione
(µmol g−1 FW)
Irrigation (I)
 FI25.08 ± 1.21 c11.96 ± 0.69 c1.72 ± 0.02 c1.00 ± 0.02 c0.50 ± 0.009 c
 MD26.38 ± 1.30 b13.79 ± 0.96 b2.79 ± 0.04 b1.96 ± 0.03 b0.98 ± 0.015 b
 SD34.13 ± 0.98 a17.15 ± 0.70 a3.27 ± 0.06 a2.21 ± 0.04 a1.10 ± 0.011 a
Foliar (F)
 TW26.00 ± 1.47 d12.46 ± 1.05 d2.43 ± 0.20 d1.62 ± 0.18 d0.81 ± 0.090 d
 Spm27.50 ± 0.80 c13.71 ± 0.94 c2.53 ± 0.22 c1.69 ± 0.15 c0.84 ± 0.092 c
 Spd28.53 ± 1.31 b14.93 ± 0.75 b2.64 ± 0.24 b1.75 ± 0.19 b0.87 ± 0.091 b
 Put31.23 ± 1.92 a15.94 ± 1.06 a2.77 ± 0.26 a1.83 ± 0.16 a0.91 ± 0.094 a
Interaction (I × F)
FITW17.7 ± 0.21 k8.40 ± 0.13 j1.66 ± 0.009 j0.46 ± 0.006 k0.92 ± 0.007 k
Spm19.1 ± 0.13 i9.23 ± 0.15 i1.69 ± 0.006 j0.48 ± 0.007 j0.97 ± 0.008 j
Spd20.4 ± 0.17 i10.5 ± 0.11 h1.73 ± 0.008 i0.51 ± 0.004 i1.01 ± 0.009 i
Put22.6 ± 0.15 h11.7 ± 0.19 g1.79 ± 0.009 h0.54 ± 0.005 h1.08 ± 0.006 h
MDTW27.8 ± 0.19 g13.2 ± 0.15 f2.62 ± 0.008 g0.91 ± 0.006 g1.82 ± 0.005 g
Spm30.0 ± 0.23 f14.3 ± 0.19 e2.74 ± 0.009 f0.96 ± 0.007 f1.82 ± 0.007 f
Spd30.8 ± 0.25 e14.8 ± 0.18 e2.82 ± 0.007 e0.99 ± 0.008 e1.99 ± 0.006 e
Put31.9 ± 0.22 d15.4 ± 0.14 d2.97 ± 0.009 d1.04 ± 0.009 d2.08 ± 0.009 d
SDTW32.5 ± 0.26 d15.8 ± 0.19 d3.02 ± 0.009 d1.06 ± 0.008 d2.12 ± 0.007 d
Spm33.4 ± 0.24 c17.6 ± 0.17 c3.17 ± 0.011 c1.09 ± 0.007 c2.17 ± 0.009 c
Spd34.4 ± 0.28 b19.5 ± 0.19 b3.37 ± 0.012 b1.12 ± 0.006 b2.23 ± 0.011 b
Put39.2 ± 0.29 a20.7 ± 0.12 a3.53 ± 0.011 a1.15 ± 0.008 a2.30 ± 0.012 a
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001
I × F6<0.001<0.001<0.0010.0090.002
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 5. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the activities of enzymatic antioxidants of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 5. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the activities of enzymatic antioxidants of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorPeroxidase (A470 min−1 mg−1 Protein)Catalase (A240 min−1 mg−1 Protein)Ascorbate Peroxidase (A290 min−1 mg−1 Protein)Superoxide Dismutase (A560 min−1 mg−1 Protein)Glutathione Reductase (A340 min−1 mg−1 Protein)
Irrigation (I)
 FI1.29 ± 0.09 c48.18 ± 1.55 c50.71 ± 2.18 c5.05 ± 0.17 c28.23 ± 1.78 c
 MD1.99 ± 0.21 b64.33 ± 1.91 b70.54 ± 2.51 b6.96 ± 0.27 b45.22 ± 2.19 b
 SD2.30 ± 0.14 a70.43 ± 1.94 a78.01 ± 1.94 a7.67 ± 0.36 a51.61 ± 2.52 a
Foliar (F)
 TW1.53 ± 0.21 d54.23 ± 3.21 d58.83 ± 3.60 d5.85 ± 0.49 d36.20 ± 4.77 d
 Spm1.76 ± 0.06 c59.90 ± 2.75 c65.10 ± 2.31 c6.46 ± 0.39 c41.53 ± 3.52 c
 Spd1.99 ± 0.22 b62.91 ± 2.81 b68.16 ± 2.89 b6.71 ± 0.58 b42.91 ± 4.09 b
 Put2.09 ± 0.30 a66.70 ± 3.28 a73.43 ± 3.87 a7.18 ± 0.65 a46.00 ± 7.11 a
Interaction (I × F)
FITW0.81 ± 0.06 h40.7 ± 0.22 l36.8 ± 0.56 k4.27 ± 0.032 l20.4 ± 0.33 k
Spm0.83 ± 0.07 h43.7 ± 0.23 k42.2 ± 0.55 j4.46 ± 0.036 k22.6 ± 0.35 j
Spd1.25 ± 0.05 g46.2 ± 0.25 j47.0 ± 0.59 i4.78 ± 0.056 j25.2 ± 0.36 i
Put1.48 ± 0.03f51.7 ± 0.36 i58.1 ± 0.66 h5.38 ± 0.054 i31.2 ± 0.39 h
MDTW1.59 ± 0.02 ef53.9 ± 0.38 h60.8 ± 0.69 g5.75 ± 0.062 h36.0 ± 0.42 g
Spm1.79 ± 0.03 de58.9 ± 0.37 g70.2 ± 0.72 f6.39 ± 0.052 g42.7 ± 0.46 f
Spd1.94 ± 0.04 cd63.1 ± 0.34 f73.2 ± 0.79 e6.62 ± 0.055 f43.8 ± 0.48 e
Put2.00 ± 0.04 c65.9 ± 0.39 e76.6 ± 0.86 d7.08 ± 0.056 e46.3 ± 0.52 d
SDTW2.20 ± 0.06 b68.1 ± 0.36 d78.9 ± 0.86 c7.55 ± 0.058 d52.2 ± 0.56 c
Spm2.66 ± 0.06 a77.1 ± 0.37 c82.9 ± 0.88 b8.54 ± 0.059 c59.3 ± 0.59 b
Spd2.80 ± 0.08 a79.4 ± 0.42 b84.3 ± 0.99 a8.75 ± 0.075 b59.7 ± 0.57 ab
Put2.81 ± 0.06 a82.5 ± 0.49 a85.6 ± 0.96 a9.10 ± 0.075 a60.5 ± 0.62 a
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001
I × F6<0.001<0.001<0.001<0.001<0.001
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 6. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the anatomical characteristics of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 6. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the anatomical characteristics of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorMidrib
Length (μm)		Midrib
Width (μm)		Vascular Bundle Length (μm)Vascular Bundle Width (μm)Phloem
Thickness (μm)		Xylem
Thickness (μm)		Collenchyma Thickness (μm)Vessel Diameter
(μm)		Number of Xylem Rows in Midvein Bundle
Irrigation (I)
 FI1927 ± 22 a1881 ± 19 a1217 ± 21 a1354 ± 13 a122.3 ± 5 a218.1 ± 6 a749.5 ± 7 a46.3 ± 3 a47.5 ± 3 a
 MD1353 ± 25 b1462 ± 20 b881 ± 15 b999 ± 15 b63.84 ± 3 b85.79 ± 4 b387.8 ± 3 b28.5 ± 2 b35.5 ± 2 b
 SD818 ± 17 c862 ± 14 c381 ± 12 c545 ± 8 c42.56 ± 4 c69.16 ± 3 c297.5 ± 4 c19.0 ± 1 c24.6 ± 2 c
Foliar (F)
 TW1248 ± 26 b1266 ± 19 b775 ± 12 b848 ± 11 b63.84 ± 4 b99.29 ± 4 b460.5 ± 4 b27.7 ± 2 b32.6 ± 3 b
 Put1484 ± 30 a1537 ± 19 a878 ± 14 a1084 ± 13 a88.66 ± 5 a156.1 ± 6 a496.0 ± 5 a34.8 ± 3 a39.7 ± 3 a
Interaction (I × F)
FITW1872 ± 18 b1818 ± 19 b1163 ± 16 b1272 ± 24 b106.4 ± 3 b170.2 ± 3 b744 ± 8 b42.8 ± 2 b46 ± 2 b
Put1981 ± 16 a1945 ± 23 a1272 ± 18 a1436 ± 27 a138.3 ± 4 a266.0 ± 5 a755 ± 9 a49.9 ± 3 a49 ± 3 a
MDTW1236 ± 21 d1254 ± 24 d799 ± 14 d818 ± 16 d53.20 ± 2 d74.48 ± 2 d372 ± 5 d23.8 ± 2 d30 ± 1 d
Put1472 ± 24 c1672 ± 18 c963 ± 18 c1181 ± 20 c74.48 ± 4 c117.1 ± 3 c404 ± 7 c33.3 ± 3 c42 ± 3 c
SDTW636 ± 12 f727 ± 16 f363 ± 9 f454 ± 8 f31.92 ± 2 e53.20 ± 2 f266 ± 3 f16.6 ± 1 f21 ± 1 f
Put999 ± 19 e998 ± 20 e399 ± 11 e636 ± 12 e53.20 ± 3 d85.12 ± 4 e329 ± 4 e21.4 ± 2 e28 ± 2 e
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001
I × F6<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001<0.001
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
Table
Table 7. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the agronomic traits of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Table 7. Impacts of exogenously applied spermine (Spm), spermidine (Spd), and putrescine (Put) compared to tap water (TW) on the agronomic traits of sesame grown under three irrigation regimes; full irrigation (FI), mild drought (MD), and severe drought (SD) over two growing seasons (2020 and 2021).
Studied FactorPlant Height (cm)Leaf Area (cm2)No. of Capsules Plant−11000-Seed Weight (g)Seed Yield (Kg ha−1)Oil Content (%)Crop Water Productivity
Irrigation (I)
 FI150.8 ± 2.21 a38.80 ± 0.37 a68.64 ± 0.69 a3.60 ± 0.034 a1672 ± 10.25 a42.14 ± 0.20 a0.283 ± 0.001 a
 MD129.2 ± 1.63 b33.65 ± 0.59 b59.86 ± 0.81 b3.26 ± 0.029 b1540 ± 16.6 b39.60 ± 0.34 b0.348 ± 0.003 b
 SD98.32 ± 1.73 c28.09 ± 0.55 c50.41 ± 0.55 c2.94 ± 0.025 c1271 ± 12.1 c37.15 ± 0.18 c0.431 ± 0.004 c
Foliar (F)
 TW117.3 ± 4.30 d31.23 ± 1.70 d56.46 ± 2.61 d3.14 ± 0.089 d1439 ± 64.1 d38.53 ± 0.74 d0.340 ± 0.019 d
 Spm124.5 ± 4.64 c33.11 ± 1.52 c58.63 ± 2.56 c3.24 ± 0.094 c1485 ± 58.2 c39.43 ± 0.73 c0.352 ± 0.021 c
 Spd128.6 b ± 5.04 b33.94 ± 1.57 b60.48 ± 2.74 b3.30 ± 0.101 b1512 ± 58.5 b39.96 ± 0.75 b0.359 ± 0.022 b
 Put134.1 a ± 4.91 a35.77 ± 1.48 a62.98 ± 2.79 a3.40 ± 0.102 a1540 ± 58.0 a40.60 ± 0.74 a0.366 ± 0.023 a
Interaction (I × F)
FITW140.5 ± 0.62 d37.2 ± 0.12 c65.8 ± 0.35 d3.44 ± 0.012 d1652 ± 3.5 c41.2 ± 0.22 c0.280 ± 0.0002 k
Spm148.7 ± 0.66 c38.2 ± 0.16 b67.5 ± 0.38 c3.56 ± 0.016 c1662 ± 4.2 b41.9 ± 0.26 b0.282 ± 0.0001 j k
Spd153.4 ± 0.72 b39.0 ± 0.21 b69.3 ± 0.37 b3.62 ± 0.019 b1667 ± 5.3 b42.3 ± 0.24 b0.283 ± 0.0002 j
Put160.6 ± 0.76 a40.6 ± 0.26 a71.8 ± 0.36 a3.75 ± 0.021 a1706 ± 5.8 a43.1 ± 0.28 a0.289 ± 0.0005 i
MDTW121.1 ± 0.68 h30.9 ± 0.18 g55.6 ± 0.32 g3.13 ± 0.013 h1455 ± 4.6 g37.9 ± 0.27 f0.329 ± 0.0008 h
Spm128.4 ± 0.58 g33.3 ± 0.16 f58.5 ± 0.34 f3.22 ± 0.014 g1526 ± 4.7 f39.5 ± 0.31 e0.345 ± 0.0007 g
Spd131.4 ± 0.54 f34.1 ± 0.15 e60.9 ± 0.35 d3.29 ± 0.018 f1579 ± 3.5 e40.1 ± 0.35 d0.357 ± 0.0002 f
Put135.8 ± 0.67 e36.2 ± 0.13 d64.3 ± 0.39 d3.39 ± 0.016 e1597 ± 3.9 d40.8 ± 0.36 c0.361 ± 0.0008 e
SDTW90.40 ± 0.58 l25.5 ± 0.21 j47.8 ± 0.25 k2.83 ± 0.012 l1210 ± 3.9 k36.3 ± 0.29 g0.410 ± 0.0020 d
Spm96.30 ± 0.56 k27.7 ± 0.24 i49.8 ± 0.31 j3.92 ± 0.011 k1266 ± 3.6 j36.8 ± 0.27 g0.429 ± 0.0015 c
Spd100.6 ± 0.61 j28.6 ± 0.23 h51.1 ± 0.37 i2.97 ± 0.018 j1289 ± 4.3 i37.4 ± 0.24 f0.437 ± 0.0010 b
Put105.9 ± 0.69 i30.4 ± 0.28 g52.7 ± 0.39 h3.04 ± 0.017 i1317 ± 4.9 h37.8 ± 0.26 f0.447 ± 0.0013 a
ANOVAdfp-value
I2<0.001<0.001<0.001<0.001<0.001<0.001<0.001
F3<0.001<0.001<0.001<0.001<0.001<0.001<0.001
I × F60.0020.0070.0060.009<0.0010.008<0.001
Means followed by ±SE and the different letters under each studied factor are significantly different in accordance with Tukey’s HSD test (p < 0.05).
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Desoky, E.S.M.; Alharbi, K.; Rady, M.M.; Elnahal, A.S.M.; Selem, E.; Arnaout, S.M.A.I.; Mansour, E. Physiological, Biochemical, Anatomical, and Agronomic Responses of Sesame to Exogenously Applied Polyamines under Different Irrigation Regimes. Agronomy 2023, 13, 875. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13030875

AMA Style

Desoky ESM, Alharbi K, Rady MM, Elnahal ASM, Selem E, Arnaout SMAI, Mansour E. Physiological, Biochemical, Anatomical, and Agronomic Responses of Sesame to Exogenously Applied Polyamines under Different Irrigation Regimes. Agronomy. 2023; 13(3):875. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13030875

Chicago/Turabian Style

Desoky, El Sayed M., Khadiga Alharbi, Mostafa M. Rady, Ahmed S. M. Elnahal, Eman Selem, Safaa M. A. I. Arnaout, and Elsayed Mansour. 2023. "Physiological, Biochemical, Anatomical, and Agronomic Responses of Sesame to Exogenously Applied Polyamines under Different Irrigation Regimes" Agronomy 13, no. 3: 875. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13030875

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