Introduction

Climate change, coupled with global warming, is a serious problem for the agricultural sector in developing countries, especially in Pakistan. Meteorological data indicate an exceptional increase in global climate temperature of 1–2 °C by 20501. The temperature fluctuations diminished crop production due to counteracting various drastic environmental abiotic stresses, including water, heat, saline, etc2,3. Drought could harm arable land and lead to a 46% reduction in crop production by the end of the 21st century4. Its persistence depended on the plant-water-soil relationship resulting from uneven rainfall, unbalanced plant evapotranspiration, and reduced soil moisture retention5. Moisture stress inhibits plant growth, leading to impaired nutrient absorption and reduced physiological activity6.

Cotton is cultivated as a fiber crop in tropical regions worldwide with > 40 °C temperature7. Its production achieved a significant role in the food and fiber industry based on the consumption of > 120 million bales8. Unfortunately, cotton production in major producing countries like Pakistan is being hampered by global climate change, including droughts and heatwaves9. Cotton is considered an exhaustive crop and required throughout the entire vegetative–reproductive growth stages10. Water stress during the reproductive stages, referred to as reproductive drought, significantly impaired crop production. Observations proved that vegetative drought has a lesser impact (10–30%) compared to reproductive drought (50–80%) on cotton cultivation, especially during the flowering and fruit’s formation stages11. Reproductive drought decreased the morphological growth – developmental attributes, physiological parameters, anti-oxidant contents, fiber quality-related traits, and ultimately reduced the benefit-cost ratio of cotton12. Therefore, cotton cultivation may require a sustainable and organic approach to mitigate the negative impact of reproductive drought and improve the drought tolerance for higher cotton seed production.

Moringa leaf extract (MLE30) is one of the best and most effective bio-stimulant growth regulators used for enhancing metabolic performance, boosting crop yield, and quality13. The exogenous application of moringa extract may serve to improve resistance due to its potential anti-oxidant contents, alleviate relative cell damage, and improve fiber quality in cotton plants induced by reproductive drought stress, as well as normal irrigation conditions14. Moringa bio-stimulant may have the potential to manage the source-sink relationship, performing a better photosynthesis process in cotton production15. Analysis of moringa has revealed a detailed composition of various plant growth hormones (Zeatin), anti-oxidants, vitamins, and micro-macro nutrients, making it an ideal bio-stimulant growth enhancer16. It can be effectively used to enhance cotton production by well-organized utilization of the nutrient absorption system, boosting the anti-oxidant system, and performing significant physiological activities17. Moringa bio-stimulant compensates for the use of synthetic stimulants due to its cost-effectiveness and sustainable use in field crops under unfavorable environmental stress conditions18.

A foliar spray of moringa bio-stimulant may be more effective in application than other methods like seed priming, seed coating, and soil application to obtain a significant crop yield19. It is important to apply moringa spray at suitable critical stages of cotton crops, as effective for increasing tolerance under applied drought stress conditions20. To the author’s current knowledge, studies have shown the effectiveness of the moringa bio-stimulant via seed priming in the cotton crop, but there is an urgent need to check its application via foliar application at reproductive growth stages in a changing climate. Therefore, a study was planned to understand the effective use of bio-stimulants through foliar spray at various growth stages of cotton crops and their mechanism of action by observing physiological and anti-oxidant behavior to cope with the induced reproductive drought stress.

Materials and methods

Preparation of bio-stimulants Moringa, Seaweed, Nitro-phenolates

The standard procedure was followed to prepare the moringa bio-stimulant21. For this, the fresh leaves were collected from a healthy, mature moringa tree at 10:30 am from the moringa garden situated within the Experimental Research Area. The collected moringa leaves were carefully washed with distilled water and air-dried for 6 h in the Seed Science Laboratory. The leaves were then stored in a laboratory freezer at − 80 °C in a laboratory freezer for 48 h. A hand-made extraction machine was used to crush and press the chilled leaves to obtain moringa extract. The collected extract was centrifuged at 6500 rpm resolution for 20 minutes2. After this, the purified moringa extract was diluted with distilled water in the ratio of 1:30 and named as “SANJHI” bio-stimulant and commercialized in the pesticide industry. Seaweed and nitro-phenolates extracts were purchased from private limited companies Wokozim Crop Plus and Asahi Star before application in the experimental trials22.

Experimental field site, metrological data, and soil analysis

Experimental trials were examined at the Experimental Research Area, Department of Agronomy, Faculty of Agricultural Sciences & Technology, Bahauddin Zakariya University, Multan, Pakistan (71° 28′ 31′′ E, 30° 11′ 44′′ N and 129 m above sea level) during the summer seasons (1st fortnight of May) of 2023 and 2024. Multan city is included in a semi-arid region of Pakistan, and meteorological data during the cotton crop phenological growth stages of both years of the trials are presented in Fig. 1. According to the FAO classification, experimental soil is fine silty in texture, sodic haplocambids, mixed, hyperthermic soil Sindhlianwali series. Three soil samples were collected from different experimental sites and analyzed during the years 2023 and 2024 shown in Table 1.

Fig. 1
figure 1

Metrological data of cotton phenological growth stages of cotton crop during 2023 and 2024. Weather station located at Central Cotton Research Institute Multan, Pakistan.

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Table 1 Soil analysis of cotton experimental site at experimental research Area, Institute of Agronomy, faculty of agricultural sciences & Technology, Bahauddin Zakariya university of Multan, Pakistan.
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Experimental layout

This project field study was conducted for two consecutive years (2023, 2024). Experiments were designed with Randomized Complete Block Design (RCBD) with two factorial arrangements having treatments; Factor A: Foliar spray of bio-stimulants i.e., Hydro (Tap water), Moringa bio-stimulants (moringa leaf extract 1:3 MLE: Water)21, Seaweed extract (3 ml L−1)23, Nitro-phenolates (2 ml L−1)24, Factor B: Terminal reproductive drought stress (Control (irrigations applied at vegetive - reproductive principal growth stages BBCH code 10, 20, 30, 50, 60, 70), flowering drought (code 60), fruit’s formation drought (code 70)). A digital V-Tech Soil Tensiometer was used to maintain water requirement by maintaining the soil moisture contents at 100% of field capacity after flood irrigation method in each experimental plot. Bio-stimulants were sprayed at two principal growth stages following the BBCH code i.e., flowering (code 60) and fruit’s formation (code 70)25. IUB-2013 was used as the cotton test cultivar.

Crop husbandry

Pre-soaking irrigation (≥ 10 cm) was applied at the experimental area to attain the soil workable condition at 100% field capacity. The preparation of the seedbed was performed with 2 ploughings (20–30 cm) and subsequent planking (8–15 cm) using a field tractor-mounted cultivator. The treated cotton seeds were sown according to the designed trial units during the 1st fortnight of May and started harvesting (3 pickings at 22 days of intervals) during the 2nd fortnight of October–November, respectively in both years 2023 and 2024. A net plot area of ​​3.75 × 6.10 m2 was maintained in each experimental unit. The recommended cottonseed rate was 25 kg ha−1. Cotton plant density was maintained using the standard distance at row to row (2.5 feet) and plant to plant (9 inches). Three splits of urea (N) were applied at different intervals, including first-time seedbed preparation, second at 1st irrigation, and 3rd at the flowering stage (code 60) during the cotton crop growth stage. Diammonium phosphate (P) and sulfate of potash (K) were used during the seedbed preparation at recommended rates (65 and 55 kg ha−1) respectively in experimental trials. Weed protection measures were practiced by foot manuring in cotton fields. The cotton field was kept free from insect-pest disease by implementing integrated crop management, including the use of Imidacloprid (Confidor 200-SL). Moreover, uniform agronomic management practices were applied in all experimental units during both years of trials.

Observations

Anti-oxidants analysis

The standard protocols were used to measure the anti-oxidants using a nano-spectrophotometer. Three samples (5 flag leaves) were randomly collected from mature cotton plants in the early morning at 10:00 am at a temperature of 25 ± 5 °C after the application of fruit’s drought stress in the experimental studies. The collected leaves were separately packed in plastic zip bags and stored in a laboratory freezer at – 80 °C for anti-oxidant analysis. For this purpose, frozen leaf samples (0.5 g) were ground in a mortar with 1 mL of buffered extract (pH 7.3). A 1 L of phosphate buffer saline stock solution was prepared by mixing 10 mM Na2HPO4; 2 mM KH2PO4; 2.7 mM KCl; and 1.37 mM NaCl respectively. HCl was gradually mixed in phosphate buffer saline stock solution to adjust the pH 7.2. Before protein extraction, 1 µM protease inhibitor was added to the buffer solution. The grounded sample material was centrifuged into a supernatant solution by adjusting resolution at 15,000 × g for 10 min. The standard curve was plotted in a Microsoft Excel Sheet-2019 at different levels of bovine serum albumin (10, 20, 30, 40, and 50 µg mL–1) followed by mixing 400 µL Dye stock with distilled water. All samples were then placed in a vortex mixer to mix carefully and incubated for 5 min at laboratory temperature. Total soluble protein (TSP) observations were made at an absorbance of 595 nm26. The sample reactive mixture (100 µL) was prepared by adding 400 µL guaiacol (20 mM), 500 µL H2O2 (40 mM), and 2 mL phosphate (50 mM). Peroxidase observations were measured at an absorbance of 470 nm (15 s ± 5 min). For catalase (CAT), the reactive mixture was decomposed with H2O2 and then noted observations at an absorbance of 240 nm (25 s ± 5 min)27. 50 µL of reactive mixture was mixed with 1 mL nitro-blue tetrazolium (50 µM), 500 µL methionine (13 mM), 1 mL riboflavin (1.3 µM), 950 µL (50 mM) phosphate buffer, 500 µL EDTA (75 mM) followed by adapting the reaction procedure to place in the dark cabin with switching on (30 W ± 5 min). Superoxide dismutase (SOD) observations were determined at an absorbance of 560 nm after mixing the reactive mixture with NBT photo reduction and blue formazane visibility28. On the other hand, a stock solution of gallic acid was used for the standard curve for measuring the total phenolic contents (TPC). For this purpose, all the treated samples (5 mL) were filtered using 80% acetone solution up to the level of 10 mL. Each sample (20 µL) was prepared with the mixing of deionized water (1.58 mL) and Folin Ciocalteu reagents (100 µL) (25 s ± 9 min). 300 µL sodium carbonate was added to each sample and placed in the laboratory (40 °C ± 30 min). Total phenolic contents observations were noted at an absorbance of 760 nm29.

Physiological attributes

All the physiological parameters were measured using the modified formulas described below30,31,32,33;

$${\text{Specific}}\;{\text{leaf}}\;{\text{weight}}\left( {{\text{SLW}}} \right) = {\text{Leaf}}\;{\text{dry}}\;{\text{weight}}/{\text{Leaf}}\;{\text{area}}$$
$$\begin{aligned} {\text{Relative}}\;{\text{water}}\;{\text{contents}}\left( {{\text{RWC}}} \right) = & \left\{ {\left( {{\text{Fresh}}\;{\text{weight}}{-}{\text{Dry}}\;{\text{weight}}} \right)/\left( {{\text{Turgid}}\;{\text{weight}}{-}{\text{ Dry}}\;{\text{weight}}} \right)} \right\} \\ & \times 100 \\ \end{aligned}$$
$${\text{Relative}}\;{\text{membrane}}\;{\text{permeability}}\;\left( {{\text{RMP}}} \right) = \{ ({\text{EC}}_{{\text{A}}} {-}{\text{EC}}_{{\text{O}}} )/{\text{EC}}_{{\text{B}}} {-}{\text{EC}}_{{\text{O}}} )\} \times {\text{1}}00$$
$$\begin{aligned} {\text{Relative}}\;{\text{Cell}}\;{\text{Injury}}\;\left( {{\text{RCI}}} \right) = & {\text{1}}{-}\left\{ {{\text{1}} - \left( {{\text{EC}}_{{{\text{Treated}}\;{\text{sample}}\;{\text{before}}\;{\text{autoclaving}}}} /{\text{EC}}_{{{\text{Treated}}\;{\text{sample}}\;{\text{after}}\;{\text{autoclaving}}}} } \right)} \right\} \\ & /\left\{ {{\text{1}}{-}\left( {{\text{EC}}_{{{\text{Control}}\;{\text{sample}}\;{\text{before}}\;{\text{autoclaving}}}} /{\text{EC}}_{{{\text{Control}}\;{\text{sample}}\;{\text{after}}\;{\text{autoclaving}}}} } \right)} \right\} \\ & \times 100 \\ \end{aligned}$$

*EC = Electric Conductivity.

Morphological growth, development, and fiber quality-related attributes

Standard procedures described in the protocols were used to measure cotton growth-related traits, including leaf area index30 (LAI), seasonal leaf area duration (SLAD), and plant growth rate34 (CGR). Randomly, five healthy cotton plants were selected and harvested to calculate plant populations acre−1, plant height (cm), harvested bolls plant−1, average boll weight (g), and seed cotton yield (t ha−1). Twenty harvested bolls were preserved for determining the fiber-related attributes, including fiber fineness (µg inch−1), fiber strength (g tex–1), fiber uniformity (%), and staple length (mm).

Benefit-cost ratio (BCR)

The economic analysis of cotton cultivation was carried out in terms of total expenditures, net income, gross income, and benefit-cost ratio after the application of foliar bio-stimulants under terminal reproductive drought stress conditions. Total expenditure on cotton production was calculated on the cost of seed, land rent, seedbed preparation, use of fertilizers, insect-pest control measures, irrigation, picking labor, etc. On the other hand, the gross income was determined based on the local market rate of seed cotton and cottonseed in Pakistan and converted into US dollars. The following modified formulas described by35 were used to measure net income and benefit-cost ratio;

$${\text{Net}}\;{\text{income}} = {\text{Gross}}\;{\text{income}}{-}{\text{Total}}\;{\text{expenditure}}$$
$${\text{Benefit}} - {\text{cost}}\;{\text{ratio}} = {\text{Gross}}\;{\text{income}}/{\text{total}}\;{\text{expenditures}}$$

Pearson correlation and principal component analysis (PCA) biplot

Dewey and Lu36 described the procedures using the software Statistix 8.1 for the Pearson correlation and Principal component analysis biplot. This analysis involved partitioning the coefficients correlation between direct and indirect effects in the applied treatment of bio-stimulants and terminal reproductive drought stress by substituting means for random variables into outcome variables.

Statistics analysis

In this project, statistical analysis using Statistix 8.1 was performed by Fisher’s analysis of variance to organize and analyze the observed treatment data. Treatment means and years interaction differences were compared at a 0.05 probability level using Duncan’s multiple range tests37.

Results

Physiological attributes

The application of various bio-stimulants and terminal drought stress resulted in a significant improvement trend in the physiological attributes of cotton plants in both years of the project study (Fig. 2). Among bio-stimulants, moringa foliar spray achieved maximum values (11.70%) of SLW than hydro treatment under fruit’s formation drought, followed by flowering drought after control during the year 2024 compared to 2023 (Fig. 2). During the second year of the project study, terminal drought stress impaired RWC, but the treatment of moringa foliar spray enhanced the RWC (25.41%), followed by seaweed, nitro-phenolates than hydro treatments in the induced flowering drought, and fruit’s formation drought than control (Fig. 2). Likewise, RCI was noted to be maximum (2.24%) in cotton plants treated with moringa bio-stimulant as per seaweed, nitro-phenolates, and hydro treatments in flowering drought, followed by fruit’s formation drought (Fig. 2). Terminal drought stress applied to flowering and fruit’s formation stages declined RMP values of cotton plants, while moringa bio-stimulant diminished the impact of fruit’s formation drought as well as flowering drought and enhanced RMP (12.26%) as per hydro treatment (Fig. 2).

Fig. 2
figure 2

Bio-stimulants spray effected on physiological attributes of cotton at applied reproductive drought stress.

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Morphological growth attributes

Terminal reproductive drought stress significantly reduced the morphological growth attributes of cotton plants compared to the control, but moringa foliar spray during flowering and fruit’s formation resulted in a gradual improvement in LAI at 105 days after sowing (DAS) in both years of trials (2023, 2024) (Fig. 3). SLAD was reduced in the plants induced by flowering drought and fruit’s formation drought; however, treated plants with moringa bio-stimulants were noted with higher SLAD at 60, 75, 90, 105 DAS, respectively, as per treatments of seaweed, nitro-phenolates, and hydro foliar spray in the applied terminal drought stress conditions during both years (Fig. 3). The data revealed that CGR progressively increased up to 90 DAS and started to decline at 105 DAS, but the results of moringa-treated plants achieved maximum CGR values under flowering drought, followed by fruit’s formation drought after control in both years of exploration (Fig. 3). Observations also interactive effect of applied bio-stimulant and terminal drought stress on morphological attributes of cotton plants was significantly higher (Fig. 3).

Fig. 3
figure 3

Bio-stimulants spray effected on morphological growth attributes of cotton at applied reproductive drought stress.

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Anti-oxidant status

Moringa bio-stimulant triggered the higher production (14.10%) of TSP in the cotton plants compared to hydro treatment induced by fruit’s formation drought followed by flowering drought during both years of experiments (Table 2). The release of SOD was observed maximum (12.61%) after the treatment applied with foliar spray of moringa bio-stimulant than hydro treatment in the fruit’s formation drought in both years shown in Table 2. The interactive effect of applied bio-stimulant and terminal drought stress resulted in significant positive for POD contents, and moringa bio-stimulant upgraded the higher production of POD values (33.17%) in the plants than hydro treatment induced with terminal fruit’s formation drought as well as flowering drought during both years of study (Table 2). The application of moringa bio-stimulant treatment increased CAT contents (2.18%) in the cotton plants as compared to seaweed, nitro-phenolates, and hydro bio-stimulants under fruit’s formation drought followed by flowering drought than control during both years of the experimental study presented in Table 2. TPC were produced maximum (9.55%) under the plants treated with moringa bio-stimulant as per hydro treatment in the applied fruit’s formation drought during both years of study (Table 2). Table 2 presented the prominent production of anti-oxidant contents in the plants treated with bio-stimulants under terminal drought stress were noted higher.

Table 2 Bio-stimulants spray effected on anti-oxidant status of cotton at applied reproductive drought stress.
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Morphological developmental-related yield attributes

Table 3 describes the significant results of morphological development attributes in the cotton plants with the application of bio-stimulants under various terminal drought stress conditions. Maximum cotton plant populations (6.40%) were observed after foliar spray of moringa bio-stimulant as compared to seaweed, nitro-phenolates, and hydro treatments in control, followed by flowering drought and fruit’s development drought (Table 3). Observations illustrated that treatment applied moringa bio-stimulant in cotton plants obtained higher plant height (4.84%) than hydro spray in flowering drought followed by fruit’s formation drought after control conditions (Table 3). The harvested bolls plant−1 were noted maximum (2.70%) in the treated plants with moringa spray bio-stimulant as compared to hydro spray in the control condition as well as flowering drought and fruit’s formation drought (Table 3). The application of moringa spray treatment in the cotton plants achieved greater average boll weight (18.20%) compared to hydro spray in the control condition (Table 3). During the second year of trials, seed cotton yield was noted as maximum (9.72%) in the treatment of moringa bio-stimulant compared to seaweed, nitro-phenolates, and the minimum was in hydro spray under flowering drought as well as fruit’s formation drought after control conditions illustrated in Table 3.

Table 3 Bio-stimulants spray effected on morphological developmental related yield attributes of cotton at applied reproductive drought stress.
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Fiber quality attributes

Data revealed that cotton plants treated with moringa foliar spray achieved better results in fiber fineness (5.82%) compared to hydro spray under control, followed by flowering drought and fruit’s formation drought during both years of exploration (Table 4). Higher fiber strength (2.43%) was noted in the plants grown with foliar spray of moringa as compared to seaweed, nitro-phenolates, and hydro treatments in flowering drought, as well as fruit’s drought after control conditions during both years presented in Table 4. Terminal reproductive drought stress reduced the fiber uniformity, but the applied moringa bio-stimulant increased the fiber uniformity (1.09%) compared to hydro spray under control, as well as flowering drought followed by fruit’s drought in both years of the project study (Table 4). The second year of the experiments achieved higher results, greater staple length in the plants with moringa treatment under control conditions followed by flowering drought and fruit’s formation drought (Table 4).

Table 4 Bio-stimulants spray effected on fiber quality related attributes of cotton at applied reproductive drought stress.
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Benefit-cost ratio

Economic analysis of the average of both years (2023, 2024) mentioned that the applied flowering drought and fruit’s drought achieved superior net income (2252.66 US$ ha−1) and BCR (3.97) in the treatment of moringa bio-stimulant as compared to seaweed, nitro-phenolates, and hydro spray after the control condition depicted in Table 5. Observations described that nitro-phenolates bio-stimulant resulted in the least net income and benefit-cost ratio in the applied terminal reproductive drought stress and control condition (Table 5).

Table 5 Average years (2023–2024) of cotton economic analysis.
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Principal component analysis (PCA), Biplot, and pearson correlation analysis

The applied treatment of bio-stimulant in the cotton plants under various induced terminal flowering and fruit’s formation drought stress obtained a significantly positive interaction in the observed growth, development, physiological, anti-oxidant contents, fiber quality parameters during both years (2023, 2024) of trials (Table 6). Graphical interaction described the distinct direction in the observed parameters after moringa bio-stimulant application under terminal flowering and fruit’s formation drought stress shown in Fig. 4.

Table 6 Pearson correlation interaction in the observed attributes after Bio-stimulant application in cotton crop under reproductive drought stress.
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Fig. 4
figure 4

Principal component analysis (PCA) Biplot after applied Bio-stimulants spray in cotton crop at reproductive drought stress. Plant population (PP), Plant height (PH), Harvested boll plant−1 (HB), Boll weight (BW), Cotton yield (CY), Specific leaf weight (SLW), Relative water contents (RWC), Relative cell injury (RCI), Relative membrane permeability (RMP), Total soluble proteins (TSP), Superoxide dismutase (SOD), Peroxidase (POD), Catalase (CAT), Total phenolic contents (TPC), Fiber length (FL), Fiber strength (FS), Fiber uniformity (FU), Staple length (SL). Biplot for foliar mentioned the groups having treatments i.e., Hydro (Tap water), Moringa leaf extract (MLE30), Seaweed extract (SWE), Nitro-phenolates (NP). Biplot for drought mentioned the groups having treatments i.e., Control, Flowering Drought, Fruit’s formation Drought.

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Analysis of variance (ANOVA) showed significant differences between the observed attributes after applied project treatments using RCBD factorial design under p-test (Table 7).

Table 7 Two-way ANOVA table under applied project treatments observations using factorial RCBD design at p test.
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Discussion

In this project study, the application of moringa bio-stimulant triggered the plant performance in the way of increasing trend of cotton growth-related attributes like LAI, SLAD, and CGR during the various intervals of days after sowing under applied flowering drought and fruit’s formation drought. It has been observed that this might be due to the availability of essential nutrients and “Zeatin” growth-promoting hormones in moringa extract as compared to other bio-stimulants (seaweed, nitro-phenolates, hydro) for boosting the plant drought tolerance for better photosynthesis activities38. A significant result in leaf-related growth traits played an important role as a promoting component for achieving the cotton yield in this study. Moringa foliar spray increased the production of photo-assimilates and transportation in the plant leaves under terminal drought stress conditions39. Moringa bio-stimulant acted as a catalyst to ensure a better connection between the source and sink during the photosynthesis process under normal conditions, as well as terminal reproductive drought stress40. The difference in the efficiency of growth attributes of plants treated with moringa bio-stimulant compared to others may be due to providing a suitable platform for utilizing natural input resources41. The applied moringa foliar spray obtained higher values in LAI, SLAD, and CGR in the plants might be due to enhanced photosynthetic activities, cell division, and cell enlargement, respectively, for the exploitation of resources and higher consumption of solar radiation during the flowering drought and fruit’s formation drought42.

The applied terminal reproductive drought stress triggered the release of potential anti-oxidant contents against reactive oxygen species (ROS) after bio-stimulant application in cotton plants. Foliar spray of moringa bio-stimulant in cotton plants, noted with maximum production of TSP, SOD, POD, CAT, and TPC, may be performed as protective anti-oxidant defensive reagents, helping in diminishing the ROS molecules, including hydrogen peroxide, hydroxyl radical, superoxide anion radical during flowering drought and fruit’s formation drought43. Cotton plants grown in the applied terminal reproductive drought stress resulted in greater anti-oxidant values compared to control conditions might be due to the use of moringa bio-stimulant, boosting the plant tolerance as compared to seaweed, nitro-phenolates, and hydro foliar spray during both years of the project study44. Moringa foliar spray triggered higher anti-oxidant production in the plants might be due to the presence of Zeatin hormones for tolerance against terminal reproductive drought stress conditions during both years 2023 and 20242.

Terminal drought stress impaired the physiological behavior of cotton plants might be due to the loss of turgor pressure45. However, moringa bio-stimulant compensated for its damaging impact by increasing the specific leaf weight and relative water contents might be due to minimum evapotranspiration loss in the plant’s leaves planted under flowering and fruit’s formation drought stress conditions46. Cotton plants noted with less relative cell injury after the application of moringa treatments might be triggered by increasing the tolerance behavior to face the induced terminal reproductive drought stress conditions33. Observations proved the relative cell injury may be due to the genetic characteristics in the cotton plants and depicted minimum relative cell injury after moringa foliar spray under the unfavorable environment of terminal reproductive drought stress conditions in this experimental study47. The increasing trend in relative membrane permeability treated with moringa bio-stimulant may lead to the alteration in the potential induced drought stress and maintain the stability in the cotton plants under flowering drought and fruit’s formation drought48.

A significantly higher plant population was observed in the control condition, followed by flowering drought and fruit’s formation drought, respectively. This may be due to effective management of the distance between plants and rows in the cotton field to ensure better performance during morphological growth and development processes49. The height of cotton plants that can be observed as a genetic trait and maximum values noted after the moringa treatment may be due to Zeatin hormones, which maintained node formation and shortened the nodal distance to produce healthy bolls’ formation50. Harvesting boll’s plant−1 is the final response of the cotton plant, observing maximum treated with foliar spray of moringa bio-stimulant might be due to the synchronized formation of primary and secondary branches under control conditions, as well as terminal reproductive drought stress10. Observations proved that moringa application enhanced the cotton boll’s weight might be due to improved efficient absorption of nutrients and their transport from vegetative stages to reproductive boll development stage under unfavorable conditions of flowering drought and fruit’s formation drought stress during both years of experiments14. Seed cotton yield is the final stage of the reproductive stage, and its outcome indicates the combined results of cotton plants, which were observed to be greater in the moringa-treated plants, might be due to the better utilization of natural resources and mitigating the reproductive drought stress by the potential anti-oxidant defense system and better physiological attributes during both years of this project study31.

Cotton fiber quality is a standard, built-in characteristic that can be improved to some extent by inducing exogenous applications of bio-stimulants51. Fiber-related attributes were reduced in the applied terminal reproductive drought stress, but moringa foliar spray significantly enhanced fiber fineness, fiber strength, fiber uniformity, and staple length, which may be due to providing favorable conditions for achieving better maturity during the phenological growth stages of the cotton crop during the flowering drought, followed by fruit’s formation drought after the control condition52.

The project study showed that the adaptation of moringa to bio-stimulants can be effective due to cost-effectiveness in terms of inputs and higher net income compared to seaweed, nitro-phenolates, hydro treatments under control, followed by terminal reproductive droughty stress conditions13. The higher cost-benefit ratio of foliar spray application of moringa bio-stimulant was found to be a highly cost-effective, sustainable, and environmentally friendly approach to enable cotton cultivation under induced drought stress flowering and fruit’s formation conditions in arid and semi-arid regions of the world53.

Conclusion

The finding of this project study is recommended that two foliar spray of moringa bio-stimulant (MLE30) at principal growth stages of flowering (code 60) and fruit’s formation (code 70) could be effective in achieving higher seed cotton yields cotton productivity, fiber quality and net income by upgrading the anti-oxidant status and mitigating relative water contents, relative cell injury, relative membrane permeability under unfavorable environmental drought conditions.