Effects of growth regulators on physiology of sesame (Sesamum indicum L.)

Introduction

Sesame (Sesamum indicum L.) dubbed the "Queen of oilseed crops, it is widely recognized as til, gingeli, sim and is the most ancient significant oilseed crop of the tropics. It is thought that sesame likely originated in Africa and It is classified in the order Tubiflorae and family Pedaliaceae, serving as a significant oilseed crop grown in both tropical and temperate regions globally for its high-grade oil (Chung et al., 2003) [5] . Sesame (Sesamum indicum L.) is known for its significant nutritional benefits, therapeutic qualities, and various industrial uses and it acts as a significant source of edible oil, nutritious nourishment, and conventional medicine (Pathak et al., 2014) [11] . India leads in sesame cultivation area globally, covering 15.31 lakh hectares with an annual production of 8.29 lakh tonnes and average productivity of 541 kg ha⁻¹. In Maharashtra, sesame is cultivated across 0.36 lakh hectares, with an annual production of 0.13 lakh tonnes and average productivity of 373 kg ha⁻¹ (Department of Agriculture & Farmers Welfare, GOI (2025) GA₃ is an occurring plant hormone that significantly influences cell elongation and overall plant growth (Taiz et al., 2015) [15] . Many studies have proved its role in improving plant development and crop yield. Its success depends on the right dosage at the right time and at the right environmental conditions (Thuc et al., 2021) [16] . Some studies have shown that Naphthalene acetic acid (NAA) had stimulating effect on various oil seeds including sesame (Govindan et al., 2000) [8] . It controls physiological processes such as cell elongation, cell division, rooting, fruit setting and prevention of flower and fruit drop (Rademacher, 2015; Basuchaudhuri, 2016) [4,13] . Salicylic Acid (SA) is also involved in the regulation of physiological processes and has been investigated for its potential to improve crop performance under abiotic stress conditions (Yousefzadeh Najafabadi et al., 2017) [17] . Although individual growth regulator effects are documented, comparative research on the influence of NAA, GA₃, and SA on the physiological characteristics, growth dynamics, yield attributes, and oil content of sesame is limited. Therefore, this investigation was conducted to systematically evaluate how targeted foliar application of individual growth regulators influences the morphophysiological growth, yield attributes, and oil content of sesame variety AKT 64.

Material and Methods

The field experiment was conducted during Kharif of 2025 at the Department of agricultural botany research farm of Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra, India. The sesame variety AKT 64, characterized by its early maturity and high yield potential, was utilized. Sowing was done manually in a Randomized Block Design (RBD) with three replications on June 23, 2025, using a seed rate of 2.5 kg ha⁻¹ by maintaining a plant spacing of 30 cm × 10 cm. The foliar treatments applied at 30, 45, and 60 days after sowing (DAS): T₁: Control; T₂: NAA @ 50 ppm; T₃: NAA @ 100 ppm; T₄: NAA @ 200 ppm; T₅: GA₃ @ 50 ppm; T₆: GA₃ @ 100 ppm; T₇: GA₃ @ 200 ppm; T₈: Salicylic Acid @ 200 ppm; T₉: Salicylic Acid @ 500 ppm; and T₁₀: Salicylic Acid @ 1000 ppm, were evaluated under the study Standard. Cultural and plant protection practices were maintained throughout the crop growth period to keep the field weeds and pest free. Five representative plants were randomly selected and tagged in each net plot (3.00 m × 1.50 m) to record morphological observations viz., days to 50% flowering and plant height, number of branches per plant, leaf area, leaf area index, at 25, 40, 55, and 70 DAS. At harvest, five plants were randomly selected and tagged from each net plot to record yield attributes: number of capsules plant -1 , number of seeds capsule -1 , seed yield plant -1 (g), 1000-seed weight (g), and harvest index (%). All recorded data were subjected to statistical Analysis of Variance (ANOVA) for RBD as outlined by Panse and Sukhatme (1954) [12] , and Critical Differences (CD) at a 5% probability level were computed.

Results and Discussion

Morphological Growth Parameters

Foliar application of different growth regulators significantly increased plant height, number of branches, leaf area and leaf area index from 40 DAS onwards over the control. At 25 DAS, treatment differences were nonsignificant, reflecting the vegetative baseline before foliar applications.

Plant Height

Significantly highest plant height was recorded under treatment T₆ (GA₃ @ 100 ppm) at 40, 55, and 70 DAS, reaching 104.60 cm at 70 DAS (Table 1). This represented an increase of 13.8% over the control (T₁, 91.89 cm).

Treatment T₆ was statistically at par with T₇ (GA₃ @ 200 ppm, 103.83 cm) and T₄ (NAA @ 200 ppm, 103.31 cm).

The increase in plant height may be attributed to the beneficial role of GA₃ in promoting cell division and cell elongation, which enhances internodal growth and overall vegetative development of sesame Sonia et al., (2024) [14] ; Abdelaal et al., (2025).

Number of Branches Plant⁻¹

The number of branches plant⁻¹ at harvest ranged from 3.16 to 6.92 (Table 1). Significantly highest branch count was observed in treatment T₆ (GA₃ @ 100 ppm, (6.92), which was at par with T₇ (GA₃ @ 200 ppm, 6.38) and superior to all other treatments. The increase in number of branches may be attributed to the beneficial role of GA₃ in promoting cell division and elongation, which enhances vegetative growth and facilitates the development of lateral branches Angel et al., (2022) [3] .

Days to 50% Flowering

Foliar application of growth regulators significantly hastened reproductive transition (Table 1). Earliest flowering was recorded in treatment T₇ (GA₃ @ 200 ppm, (39.33 days), followed by T₅ (GA₃ @ 50 ppm, (39.67 days) and T₆ (GA₃ @ 100 ppm, (40.33 days), compared to the control, T₁ (44.00 days). The earlier flowering observed under GA₃ treatments in the present investigation may therefore be attributed to the stimulatory effect of gibberellic acid on reproductive development and phenological advancement of sesame Sonia et al., (2024) [14] . [1,9] . [3] .

Yield and Yield Attributes

Yield and yield attributes of sesame were significantly influenced by the foliar application of NAA, GA₃ and SA (Table 4). The highest number of capsules plant⁻¹ (47.40) was recorded under treatment T₆ (GA₃ @ 100 ppm), which represents a 39.9% increase over the control (33.84). However, T₆ was found statistically at par with treatments T₇ (44.80 capsules), T₄ (42.67 capsules) and T₅ (41.37 capsules).

Similarly, the number of seeds capsule⁻¹ was maximized under treatment T₆ (68.23), which was superior to the control (53.74) and statistically at par with T₇ (67.86), T₄ (66.21), T₅ (64.15), T₃ (62.00) and T₂ (59.98). The 1000seed weight ranged from 2.32 g in the control to 3.34 g under T₆, showing a significant improvement with GA₃ application. Treatment T₆ recorded the highest 1000-seed weight, followed by T₇ (3.21 g), T₅ (3.09 g) and T₄ (3.01 g). Economic seed yield plant⁻¹, which integrates all growth and reproductive processes, was significantly highest under treatment T₆ (7.23 g plant⁻¹), followed by T₇ (6.54 g plant⁻¹).

This performance represents a 77.6% increase in seed yield over the untreated control (4.07 g plant⁻¹). The harvest index also reflected this partitioning efficiency, peaking at 29.23% under T₆ compared to 20.40% in the control.

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