University of Isfahan Journal of Plant Biological Sciences 3041-9603 16 2 2024 08 22 The Effect of Exogenous Gibberellic Acid and Naphthalene Acetic Acid on Sex Determination and Yield Components of Cucumber (Cucumis sativus L.) cultivar Supernia F1 The Effect of Exogenous Gibberellic Acid and Naphthalene Acetic Acid on Sex Determination and Yield Components of Cucumber (Cucumis sativus L.) cultivar Supernia F1 55 70 29367 10.22108/ijpb.2025.144089.1393 FA Parissa Jonoubi Plant Sciences Department, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran Masoumeh Arang Plant Sciences Department, Faculty of Biological Sciences, Kharazmi University, Tehran, Iran Journal Article 2025 01 19 To investigate the effects of auxin and gibberellin on the vegetative and reproductive growth of cucumber (Cucumis sativus L. cv. supernia F1), a factorial experiment was conducted using a randomized complete block design with 9 treatments and 3 replications. The treatments included auxin in the form of naphthalene acetic acid (NAA) at concentrations of 0, 50, and 100 mg L-1 and gibberellic acid (GA3) at concentrations of 0, 25, and 50 mg L-1, which were applied as foliar sprays every ten days from the 4- to 6-leaf stage until the end of flowering. The results indicated that treatment T9 (NAA at 100 mg L-1 combined with GA3 at 50 mg L-1) resulted in the lowest number of nodes, shortest internode length, and, consequently, the lowest plant height and leaf number compared to the control. The highest female flowers were observed in treatment T8 (NAA at 100 mg L-1 combined with GA3 at 25 mg L-1) and T9. Although treatment T9 exhibited the shortest height and fewest leaves, it also had the highest number of female flowers. The control plants showed the most significant height, leaf number, and male flower count. The highest fruit yield was obtained in treatment T8. Both treatments, T8 and T9, positively influenced plant yield and the conversion of female flowers into fruits. Therefore, simultaneous application of NAA at 100 mg L-1 and GA3 at 25 or 50 mg L-1 can increase yield in cucumber. Introduction Cucumbers (Cucumis sativus L.) are a globally valuable crop in the Cucurbitaceae family and are essential for nutrition and economic stability. Their improvement in yield and fruit quality is a priority for research. Cucumber sex expression in terms of hermaphroditism, monoecy, gynoecy, and androecy is genotypically and hormonally complex and is influenced by gibberellins (GAs) and auxins. While gibberellins (GAs) and ethylene are known to play roles in sex expression—promoting maleness and femaleness, respectively—auxins are also implicated in this process. Earlier research has found that NAA inhibits male flower formation, and GA3 induces cell division. This research investigates the combined effects of NAA and GA3 on cucumber sex expression. What is the effect of foliar sprays of NAA and GA3 separately and in combination on cucumber's vegetative growth, sex expression, and yield components? This research evaluates these effects on the Cucumis sativus L. Supernia F1 cultivar. The findings are of practical significance for enhanced fruit production in protected conditions. The hypotheses are that NAA increases female flowers, GA3 increases plant height but perhaps at the cost of female flowers, and the NAA/GA3 combination maximizes sex expression for higher yields. Materials and Methods The cucumber (Cucumis sativus L. cv. supernia F1) seeds germinated under greenhouse conditions. The experiment was a randomized, complete block design with nine treatments and three replications. The treatments included NAA at 0, 50, and 100 mg L-1 and GA3 at 0, 25, and 50 mg L-1. Foliar sprays of NAA and GA3 started at growth stages 4-6 and were repeated every ten days until flowering termination with a handheld sprayer in the evenings. The plant growth parameters (plant height, leaf number, node number, internode length) were measured every 7 days, and reproductive growth parameters (female flower number, male flower number, fruit number) were measured every 3 days. The data were analyzed with SPSS software version 26 and compared by Duncan's multiple range test at a level of 5%. Results and Discussion The T9 treatment had the lowest nodes (16.25), shortest internode length (3 cm), lowest height (48.66 cm), and lowest leaves (38.33), and the control exhibited the opposite trend (21.41 nodes, 3.81 cm internode length, 81.50 cm height, 61.08 leaves). T5 treatment (NAA 50 mg L-1+ GA3 25 mg L-1) possessed the maximum stem diameter (8.83 cm), and control possessed the minimum value (6.66 cm). T8 and T9 produced the maximum number of female flowers (14.5) and had a minimum in the control (10). The control had a maximum male flower number (122.26), and T9 had a minimum of 72.30. T8 provided a maximum fruit number (12.66) and fruit set percentage (87.28%), while that of control was 7.16 fruits and 71.94% fruit set. Treatment T9 positively affected fruit yield (12), and its effect was slightly lower than that of T8. The control had a minimum number of fruits, only 7.16 per plant. These findings reveal that hormonal balance is essential for fruit sets and that T8 treatment is the most appropriate combination for a maximum fruit yield under these specific experimental conditions. The results of this research corroborate the "one hormone" hypothesis of sex determination in cucumbers, suggesting that one hormone possesses both male and female cellular receptors, which suppress one sex while enhancing the other. Gibberellins have a dual role in suppressing femaleness and enhancing maleness, while ethylene promotes femaleness and suppresses maleness. There is a balance between stem cell self-renewal and differentiation in floral organ primordia development. Treatment with GA3 suppresses ethylene biosynthesis, consequently suppresses female flower formation and induces male flower formation. GA3 induces proteolysis of CsGAIP, eliminating transcriptional repression of class- B floral homeotic genes and resulting in stamen formation. Auxins positively influence genes that initiate ethylene biosynthesis and enhance female flower formation. Conclusion The use of NAA and GA3 together has been reported to regulate cucumber sex expression, vegetative growth, and production. Optimal concentrations of both hormones can promote female flower formation and improve fruit set and, ultimately, cucumber production. These findings provide insight into the hormonal regulation of sex expression in cucumbers and have implications for maximizing cucumber production in greenhouses. To investigate the effects of auxin and gibberellin on the vegetative and reproductive growth of cucumber (Cucumis sativus L. cv. supernia F1), a factorial experiment was conducted using a randomized complete block design with 9 treatments and 3 replications. The treatments included auxin in the form of naphthalene acetic acid (NAA) at concentrations of 0, 50, and 100 mg L-1 and gibberellic acid (GA3) at concentrations of 0, 25, and 50 mg L-1, which were applied as foliar sprays every ten days from the 4- to 6-leaf stage until the end of flowering. The results indicated that treatment T9 (NAA at 100 mg L-1 combined with GA3 at 50 mg L-1) resulted in the lowest number of nodes, shortest internode length, and, consequently, the lowest plant height and leaf number compared to the control. The highest female flowers were observed in treatment T8 (NAA at 100 mg L-1 combined with GA3 at 25 mg L-1) and T9. Although treatment T9 exhibited the shortest height and fewest leaves, it also had the highest number of female flowers. The control plants showed the most significant height, leaf number, and male flower count. The highest fruit yield was obtained in treatment T8. Both treatments, T8 and T9, positively influenced plant yield and the conversion of female flowers into fruits. Therefore, simultaneous application of NAA at 100 mg L-1 and GA3 at 25 or 50 mg L-1 can increase yield in cucumber. Introduction Cucumbers (Cucumis sativus L.) are a globally valuable crop in the Cucurbitaceae family and are essential for nutrition and economic stability. Their improvement in yield and fruit quality is a priority for research. Cucumber sex expression in terms of hermaphroditism, monoecy, gynoecy, and androecy is genotypically and hormonally complex and is influenced by gibberellins (GAs) and auxins. While gibberellins (GAs) and ethylene are known to play roles in sex expression—promoting maleness and femaleness, respectively—auxins are also implicated in this process. Earlier research has found that NAA inhibits male flower formation, and GA3 induces cell division. This research investigates the combined effects of NAA and GA3 on cucumber sex expression. What is the effect of foliar sprays of NAA and GA3 separately and in combination on cucumber's vegetative growth, sex expression, and yield components? This research evaluates these effects on the Cucumis sativus L. Supernia F1 cultivar. The findings are of practical significance for enhanced fruit production in protected conditions. The hypotheses are that NAA increases female flowers, GA3 increases plant height but perhaps at the cost of female flowers, and the NAA/GA3 combination maximizes sex expression for higher yields. Materials and Methods The cucumber (Cucumis sativus L. cv. supernia F1) seeds germinated under greenhouse conditions. The experiment was a randomized, complete block design with nine treatments and three replications. The treatments included NAA at 0, 50, and 100 mg L-1 and GA3 at 0, 25, and 50 mg L-1. Foliar sprays of NAA and GA3 started at growth stages 4-6 and were repeated every ten days until flowering termination with a handheld sprayer in the evenings. The plant growth parameters (plant height, leaf number, node number, internode length) were measured every 7 days, and reproductive growth parameters (female flower number, male flower number, fruit number) were measured every 3 days. The data were analyzed with SPSS software version 26 and compared by Duncan's multiple range test at a level of 5%. Results and Discussion The T9 treatment had the lowest nodes (16.25), shortest internode length (3 cm), lowest height (48.66 cm), and lowest leaves (38.33), and the control exhibited the opposite trend (21.41 nodes, 3.81 cm internode length, 81.50 cm height, 61.08 leaves). T5 treatment (NAA 50 mg L-1+ GA3 25 mg L-1) possessed the maximum stem diameter (8.83 cm), and control possessed the minimum value (6.66 cm). T8 and T9 produced the maximum number of female flowers (14.5) and had a minimum in the control (10). The control had a maximum male flower number (122.26), and T9 had a minimum of 72.30. T8 provided a maximum fruit number (12.66) and fruit set percentage (87.28%), while that of control was 7.16 fruits and 71.94% fruit set. Treatment T9 positively affected fruit yield (12), and its effect was slightly lower than that of T8. The control had a minimum number of fruits, only 7.16 per plant. These findings reveal that hormonal balance is essential for fruit sets and that T8 treatment is the most appropriate combination for a maximum fruit yield under these specific experimental conditions. The results of this research corroborate the "one hormone" hypothesis of sex determination in cucumbers, suggesting that one hormone possesses both male and female cellular receptors, which suppress one sex while enhancing the other. Gibberellins have a dual role in suppressing femaleness and enhancing maleness, while ethylene promotes femaleness and suppresses maleness. There is a balance between stem cell self-renewal and differentiation in floral organ primordia development. Treatment with GA3 suppresses ethylene biosynthesis, consequently suppresses female flower formation and induces male flower formation. GA3 induces proteolysis of CsGAIP, eliminating transcriptional repression of class- B floral homeotic genes and resulting in stamen formation. Auxins positively influence genes that initiate ethylene biosynthesis and enhance female flower formation. Conclusion The use of NAA and GA3 together has been reported to regulate cucumber sex expression, vegetative growth, and production. Optimal concentrations of both hormones can promote female flower formation and improve fruit set and, ultimately, cucumber production. These findings provide insight into the hormonal regulation of sex expression in cucumbers and have implications for maximizing cucumber production in greenhouses.

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