Effect of different levels of ethephon on growth, sex expression, yield and quality of pumpkin (Cucurbita maxima L.) under summer temperature conditions

Introduction

Pumpkin (Cucurbita maxima L) is a monoecious plant. Pumpkin 2n = 40, is native to warmtemperate regions of South America. Plants are large, usually viney and branched, with branched tendrils & foliage is stiffly hairy. Botanically, pumpkin is an annual, monoecious, tendril-bearing vine with a vigorous growth habit. The plant produces large, lobed leaves and extensive root systems that enable efficient nutrient uptake. Being monoecious, it bears staminate and pistillate flowers separately on the same plant, with male flowers usually appearing 7 to 10 days earlier and in greater numbers than female flowers. This skewed sex ratio, often ranging from 10:1 to 25:1, is one of the primary physiological constraints limiting fruit set and yield. Pollination is entomophilous and largely dependent on honeybees and other wild pollinators. The fruits are variable in size, shape, and skin colour, ranging from round to oblong and from green to orange at maturity. The fruit flesh is typically deep yellow to orange due to high β-carotene content. Plant growth regulators, particularly ethylene-releasing compounds like ethephon (2chloroethylphosphonic acid), have been shown to influence sex expression by promoting pistillate flowers and suppressing staminate ones. This study aimed to evaluate the optimal concentration and stage of Ethephon application to improve growth, flowering behavior, yield, and quality of pumpkin under summer conditions. Ethephon, an ethylene-releasing chemical, promotes the development of pistillate flowers while delaying staminate flowers in monoecious cucurbits. Ethephon-treated pumpkin produced a significantly higher number of female flowers (4) compared to without treatment (2.5) (Li et al. 2021) Ethephon, 2-chloroethylphosphonic acid, is a synthetic plant growth regulator that releases ethylene upon metabolism within plant tissues [12] .

International Journal of Advanced Biochemistry Research 2026; SP-10(7): 646-654

Once absorbed, ethephon breaks down at cellular pH to liberate ethylene, phosphate, and chloride ions. The released ethylene mimics the physiological action of endogenous ethylene and influences multiple developmental processes including seedling growth, apical dominance, senescence, and sex expression. Thus this study aimed to study the effect of different levels of Ethephon at 2 and 4 leaves stage.

Materials and Methods

The experiment was conducted from March to June 2025 at the Vegetable Research Farm, SHUATS, Prayagraj. The soil was sandy loam with neutral pH. The local variety Sadabahar was used. The experiment followed a Randomized Block Design with 11 treatments and 3 replications. Standard cultural practices (FYM 25 t/ha, recommended NPK, irrigation, weeding) were followed. Observations on growth (vine length, leaves, nodes), flowering (days to first male/female flower, sex ratio), yield (fruit weight, yield/plant, yield/ha), quality (TSS, vitamin C, acidity, shelf life), and economics were recorded. Data were statistically analyzed using ANOVA.

Treatments

Observations Recorded A. Growth Parameters Days to seed germination

Recorded as the number of days taken from sowing to the emergence of the first seedling (radicle emergence) under each treatment.

No. of leaves

The number of fully expanded leaves per plant was recorded at specific intervals (or at last harvest) by counting on randomly selected plants. The mean number of leaves was calculated and expressed as leaves per plant.

No. of Nodes/plant at Last Harvest

Number of nodes on the main vine or stem was counted at the final harvest stage on randomly selected plants.

The total length of the vine from the base to the tip was measured using a measuring tape or scale at the final harvest and expressed in meters.

Plant spread was measured in two directions (east-west and north-south) using a measuring scale. The average of both directions was calculated and expressed in meters. or total fruit weight per plant/plot was recorded using a digital balance and expressed in kilograms.  Fruit diameter (cm): Measured using a vernier caliper or measuring scale across the widest part of the fruit.  Fruit thickness (cm): Measured as the thickness of the fruit (flesh or overall) using a measuring instrument.

B. Flowering Parameters

D. Quality Parameters:

 Total Soluble Solid (TSS °Brix): Determined using a hand refractometer and expressed in °Brix.  Moisture content (%): Determined by oven-drying method (weight loss on drying) and expressed as percentage.  Fibre content (%): Estimated using standard laboratory procedures for crude fibre analysis.  Estimation of Acidity (%): The acidity was determined using the standard titration method, as outlined by Ranganna (1986) [20] . The acidity was calculated and expressed as a percentage of citric acid equivalent using the following formula:

Estimation of Vitamin C (Ascorbic Acid)

Vitamin C content was estimated by the 2,6-dichlorophenol indophenol dye titration method as described by A.O.A.C. (2000). The ascorbic acid content was expressed as mg per 100 g pulp using the following formula:

The shelf life of fruits was assessed by storing harvested fruits at room temperature and tracking the number of days until they were no longer acceptable for consumption due to spoilage.

F. Insect Pest and Disease Incidence

The incidence of major insect pests and diseases was recorded at weekly intervals starting from 20 days after sowing until final harvest.

Result and Discussion

Growth Parameters Days to Seed germination

The results pertaining on days to germinate of pumpkin are presented in Table 1. It was evident from analysis that days to germinate in plant was influenced by sowing time, temperature & depth of seed sown. There was nonsignificant difference present among the germination interval of the seeds. It was found that T4-Ethephon @150ppm had taken minimum days to germinate (7.50 days).

The number of days to germination is an important character. Which indicate earliness or lateness of the crop in general. Better germination in this hybrid may be due to genetic potential or having the better permeability of seed coat to water and hence earlier initiation of germination. The early and late germination help in the occurrence of early/late flush of crop which is advantageous for market to fetch the higher price. The view was supported by Kumar R. et al. (2019) in bottle gourd [9] .

No. of leaves

The results pertaining to number of leaves at last harvest of pumpkin (Kohra) are presented in Table 1. It was evident from the analysis that the number of leaves at last harvest was significantly influenced by the application of different concentrations of Ethephon. The F-test was found to be significant. Among the different treatments, the maximum number of leaves (35.6) at last harvest was recorded with T₁₀ -Ethephon @350 ppm, followed by T₉ -Ethephon @300 ppm (35.0) and T₈ -Ethephon@ 250 ppm (34.5). The minimum number of leaves was recorded in T₃ -Ethephon@ 250 ppm (30.6), which was statistically at par with the control (T₀ -Water spray, 30.8).

The number of leaves at last harvest is an important growth character which directly contributes to the photosynthetic capacity and overall vigor of the plant. The significant improvement in leaf number due to higher concentrations of Ethephon (especially 300 and 350 ppm) may be attributed to the role of ethylene in regulating vegetative growth, delaying senescence and enhancing cell division and expansion in leaves. These findings agree with earlier workers who reported significant enhancement in leaf number through plant growth regulators in cucurbitaceous crops. Similar results were recorded by Kumar R et al. (2019) [9] .

No. of Nodes/Plant at Last Harvest

The results pertaining to number of nodes per plant at last harvest of pumpkin (Kohra) are presented in Table 1. It was evident from the analysis that the number of nodes per plant at last harvest (100 DAS) was not significantly influenced by the application of different concentrations of Ethephon as the F-test was found to be non-significant (NS).

Although non-significant, the maximum number of nodes per plant (29.7) was recorded with T₆-Ethephon @150 ppm, which was closely followed by the control (T₀ Water spray-29.1). The minimum number of nodes (23.3) was observed in T₃-Ethephon @250 ppm. All the treatments were statistically at par with each other. Even though the effect was non-significant in the present study, the slight numerical increase in node number at lower concentration of Ethephon (150 ppm) indicates a possible mild promontory effect of ethylene on vegetative node production during early to mid-growth stages. These findings are in line with the observations of earlier researchers who reported variable response of Ethephon on nodal development in cucurbitaceous crops depending upon concentration and stage of application documented by Kumar, P., Singh, A. K., & Kumar, S. (2007).

The results pertaining to vine length at last harvest of Pumpkin (Kohra) are presented in Table 1. 2. It was evident from the analysis that the vine length at last harvest (100 DAS) was not significantly influenced by the application of different concentrations of Ethephon as the F-test was found to be non-significant (NS). Although the differences were statistically non-significant, the maximum vine length (3.5 m) was recorded with T₁₀ -Ethephon @350 ppm, followed by T₀ (Control -Water spray) and T₂ & T₇ (both 3.4 m). The minimum vine length (3.1 m) was observed in T₁ -Ethephon @150 ppm. Most of the treatments remained statistically at par with each other. These results are in conformity with the findings of earlier researchers who reported that Ethephon application had either non-significant or mild promontory effects on vine length in cucurbitaceous crops depending upon concentration, variety, and environmental conditions. The similar results were recorded by Sivappa (2003) [26,1,3,8] .

The data regarding plant spread at the last harvest of Pumpkin (Kohra) are presented in Table 1. Statistical analysis revealed that the application of different concentrations of Ethephon did not significantly affect plant spread at 80 DAS, as the F-test was non-significant. However, the maximum plant spread (6.46 m) was recorded in T₅ -Ethephon @350 ppm, followed by T₆ (Ethephon@150 ppm) at 6.00m. [22,16] .

No. of days to First Male Flower Emergence

The data pertaining to the number of days to first male flower emergence of pumpkin (Kohra) are presented in Table 4.2.2. Statistical analysis revealed that the application of different concentrations of Ethephon significantly affected the days to first male flower emergence, as the Ftest was significant.

The earliest first male flower emergence (27.6 days) was recorded in the control (water spray). Among the Ethephon treatments, the earliest was observed in T₂ (Ethephon @ 200 ppm) at 34.0 days, while the maximum delay was recorded in T₅ (Ethephon @ 350 ppm) at 39.5 days. Overall, most Ethephon treatments delayed the appearance of the first male flower compared to the control. These findings are in agreement with earlier reports suggesting that Ethephon application can modify flowering patterns in Pumpkin and other cucurbits, often delaying male flower anthesis at higher concentrations. Similar observations were documented by Sakthinathan and Swaminathan (2017) in Pumpkin [22] .

No. of days to First Female Flower Emergence

The data regarding the number of days to first female flower emergence of pumpkin (Kohra) are presented in [22,8,29] .

50% Flower Emergence

The data on 50% flower emergence of pumpkin (Kohra) are presented in Table 4 [40,18,19] .

No. of Female Flowers

The data regarding the number of female flowers per plant at 80 days after sowing (DAS) in pumpkin (Kohra) are presented in Table 4.2.5. Statistical analysis revealed a significant effect of Ethephon concentrations on the number of female flowers, as the F-test was significant.

The maximum number of female flowers (5.6) was recorded in T₉ (Ethephon @300 ppm) and T₁₀ (Ethephon @350 ppm), followed by T₁ and T₅ (5. [21,4,30] .

No. of Male Flowers

The data on the number of male flowers per plant at 80 DAS in pumpkin (Kohra) are presented in Table 4.2.6. Statistical analysis showed that Ethephon treatments significantly influenced the number of male flowers, as the F-test was significant.

The control (water spray) produced the highest number of male flowers (55.3), whereas all Ethephon treatments recorded substantially lower values ranging between 22.5 and 26.0. Among the treatments, T₄ (Ethephon @300 ppm) recorded the lowest number of male flowers (22.5). These results corroborate earlier reports highlighting the ability of ethephon to shift sex expression towards femaleness in cucurbits.Similar trends were observed by Singh et al. (2017) in pumpkin, Meena et al. (2022) in watermelon, and Chaudhary and Sharma (2014) in bitter gourd [13,2] .

Sex Expression (Male: Female Ratio)

The data on sex expression in terms of male to female (M:F) flower ratio of pumpkin (Kohra) are presented in Table 4.2.7. Statistical analysis revealed that application of different concentrations of Ethephon significantly influenced the sex ratio, as the F-test was significant. The control treatment recorded the highest male to female ratio (15.36). Among the Ethephon treatments, the lowest (most desirable) sex ratio of 4.90 was observed in T₅ (Ethephon @350 ppm), followed by T₄ (Ethephon @300 ppm) at 6.81. In contrast, T₈ (Ethephon @250 ppm) showed the highest ratio (15.95) [31,32,33] .

Yield Parameters Days to First Fruit Set

The data concerning the first fruit set of pumpkin (Kohra) are presented in [15, 34] .

Days to First Harvest

The data on days to first harvest of pumpkin (Kohra) are presented in Table 3 [35] .

The data on fruit diameter, fruit weight, and fruit thickness of pumpkin (Kohra) are presented in Table 4.3.3. Statistical analysis showed that different concentrations of Ethephon did not significantly affect fruit diameter, fruit weight, or fruit thickness, as the F-test was non-significant for all three parameters. Numerically, the maximum fruit weight (9.33 kg) was recorded in T₆ (Ethephon @150 ppm), followed by T₁₀ (9.02 kg). The highest fruit diameter (15.71 cm) was observed in T₇ (Ethephon @ 200 ppm), while the thickest fruit (4.85 cm) was found in T₉ (Ethephon @ 300 ppm). Physical fruit parameters such as diameter, weight, and thickness are important quality traits that determine market acceptability and consumer preference. Although non- [36,37,38] .

The data regarding total soluble solids (TSS), Vitamin-C content, and Acidity of Pumpkin (Kohra) are presented in Table 4.1. Statistical analysis revealed that Ethephon treatments significantly influenced TSS, while vitamin-C and acidity remained non-significant. The highest TSS (4.42°Brix) was recorded in T₈ (Ethephon @250 ppm), followed by T₉ (4.40°Brix). The maximum Vitamin-C content (11.00 mg/100 g) was observed in T₅ (Ethephon @350 ppm). [39,40,41] .

Moisture content, Fibre Content & Shelf life

The data on moisture content, fibre content, and shelf life of pumpkin (Kohra) are presented in [14,35] .

Conclusion

From the present investigation it is concluded that treatment T10-Ethephon @350 ppm (4 leaf stage) performed best in terms of vine length of 3.5 m, and number of leaves 36. However, the highest number of nodes per plant (30) was recorded in treatment T6-Ethephon @150 ppm (4 leaf stage).The highest yield was found in Treatment T4-Ethephon @300 ppm (2 leaf stage) with 8.4 t/ha. In terms of quality, treatment T6-Ethephon @150 ppm (4 leaf stage) had the highest value of Vitamin-C (11.0 mg/100 g), however TSS was highest in T8-Ethephon @250 ppm (4 leaf stage) (4.42 °Brix). Economically, T4-Ethephon @300 ppm (2 leaf stage) recorded the highest Gross Return, Net Return and Benefit-Cost Ratio of 2.58. Thus, application of Ethephon @300 ppm at 2 leaf stage can be recommended for achieving higher yield and better economic returns in Pumpkin (Cucurbita maxima).

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