International Journal of Horticulture, 2025, Vol.15, No.6, 279-289 http://hortherbpublisher.com/index.php/ijh 286 Table 8 Effect of growth hormones on diameter of roots per cutting Treatments Average root diameter per cutting (mm) 30DAP 60DAP 90DAP IBA-7,500 PPM 0.56ab 0.78ab 1.78a IBA-6,500 PPM 0.53ab 0.75abc 1.75a NAA-200 PPM 0.45b 0.67bc 1.17b NAA-400 PPM 0.49b 0.64c 1.14b IBA-400 PPM + NAA-200 PPM 0.62a 0.86a 1.66a Control 0.09a 0.33d 0.60c Mean 0.46 0.67 1.35 CV(%) 17.02 11.61 5.79 SEM(±) 0.039 0.048 0.090 F-test *** *** *** Note: ***Significant at 0.1 % level of significance, **Significant at 1% level of significance, *Significant at 5 % level of significance., DAP: Day After Planting, CV: Coefficient of variance, SEM: standard error mean 4 Discussion The present study demonstrates that auxin-based growth hormones, particularly IBA and NAA, play a crucial role in regulating shoot and root development in dragon fruit cuttings. The effectiveness of these hormones can be attributed to their regulatory role in cell division, elongation, and differentiation, which directly influence adventitious rooting and vegetative growth. Indole-3-butyric acid (IBA) is well known for stimulating root initiation by enhancing the activity of root meristematic cells and increasing carbohydrate mobilization toward rooting sites, while α-naphthaleneacetic acid (NAA) promotes both shoot and root initiation but is generally more effective in stimulating shoot proliferation and lateral root development (Sharma et al., 2020; Karakas et al., 2019). The synergistic use of IBA and NAA, as observed in this study, suggests that their complementary roles—IBA in root primordia development and NAA in enhancing shoot elongation and branching—create a balanced physiological environment for efficient propagation. This synergy may be due to the ability of auxins to act at different stages of root and shoot initiation: IBA acts as a stronger inducer of root initials, whereas NAA enhances the elongation phase and stabilizes lateral root formation. These findings are consistent with recent studies in other horticultural crops where auxins significantly improved vegetative propagation. For instance, Choudhary et al. (2021) reported that IBA treatments enhanced rooting in pomegranate stem cuttings, while Singh et al. (2022) observed synergistic effects of IBA and NAA in guava cuttings. Similar responses have been documented in kiwi (Wang et al., 2021), dragon fruit (Ali et al., 2020), and passion fruit (Silva et al., 2022), where auxin application improved both rooting percentage and root system architecture. Auxins not only initiate root primordia but also influence hormonal crosstalk with cytokinins and ethylene, thereby regulating the balance between root and shoot emergence (Li et al., 2021). This interaction is crucial, as excessive auxin without proper hormonal balance can result in callus formation rather than organized roots. The differences in hormone performance can further be explained by their concentration-dependent effects. High concentrations of IBA enhance root elongation and thickness due to increased lignification, vascular differentiation, and secondary growth of root tissues (Mahajan et al., 2020). In contrast, moderate concentrations of NAA stimulate shoot emergence by promoting apical dominance, strengthening auxin transport, and enhancing the supply of assimilates to emerging shoots (Kumar et al., 2019). These differential responses indicate that optimum concentration and type of auxin are critical for maximizing propagation success. The slower performance of untreated cuttings reflects the natural limitation of auxin biosynthesis in dragon fruit, which may not be sufficient to trigger rapid adventitious root and shoot formation. Moreover, endogenous auxins in cuttings degrade rapidly after detachment from the mother plant, leading to reduced rooting ability. This supports the view of Hussain et al. (2023) that exogenous hormone application compensates for endogenous auxin deficiencies in vegetative propagation systems, thereby standardizing and accelerating the rooting process. Environmental factors, such as temperature, humidity, and light intensity in the
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