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Plant Science Today (PST)

Research Articles

Vol. 13 No. 3 (2026)

Paclobutrazol-induced alterations in vine architecture and vascular tissue organisation in passion fruit (Passiflora edulis Sims)

DOI
https://doi.org/10.14719/pst.15535
Submitted
13 May 2026
Published
23-09-2026 — Updated on 30-09-2026
Versions

Abstract

Passion fruit (Passiflora edulis Sims) is characterised by vigorous vegetative growth and excessive vine elongation, resulting in dense canopy development, reduced light penetration and difficulties in canopy management. Among the various plant growth regulators, paclobutrazol (PBZ), a triazole-based growth retardant, is widely used to suppress excessive vegetative growth by inhibiting gibberellin biosynthesis. However, limited information is available on its effects on vine architecture and vascular tissue organisation in passion fruit. Therefore, the present investigation was undertaken to evaluate the effects of different concentrations of PBZ on vegetative growth regulation and vascular tissue modifications in passion fruit. The experiment was conducted in a randomised block design (RBD) comprising 3 treatments: PBZ at 100 ppm (T1), PBZ at 200 ppm (T2) and an untreated control (T3), with 5 replications. Morphological parameters, including internodal length, shoot diameter, shoot vigour and vine height, were recorded at different growth stages, while stem vascular tissues were examined using scanning electron microscopy (SEM). Quantitative measurements of xylem and phloem tissue areas were obtained from SEM micrographs using ImageJ software. Paclobutrazol treatments significantly (p < 0.05) suppressed vegetative growth compared with the untreated control by reducing vine elongation and internodal length while increasing shoot diameter. The untreated control recorded the greatest internodal lengths of 14.43 and 11.43 cm at weeks 3 and 9 respectively, whereas PBZ-treated plants maintained significantly shorter internodes. Treatment T1 (100 ppm) recorded internodal lengths of 3.33 and 3.36 cm, while T2 (200 ppm) recorded values of 3.53 and 3.32 cm at weeks 3 and 9, respectively. Similarly, PBZ-treated vines exhibited greater shoot thickness than the control, with T1 recording the highest shoot diameter values of 3.36 and 3.75 mm at weeks 3 and 9, respectively. Scanning electron microscopy image analysis using ImageJ software revealed a more compact vascular tissue organisation in PBZ-treated plants. Treatment T2 exhibited lower phloem and xylem tissue areas of 0.176 and 0.504 µm² respectively, compared with the untreated control, which recorded phloem and xylem areas of 0.842 and 2.120 µm² respectively. The reduction in vascular tissue area under PBZ treatments indicated restricted vascular expansion and reduced vegetative vigour. Among the treatments, PBZ at 100 ppm effectively regulated vegetative growth while maintaining greater shoot thickness, whereas PBZ at 200 ppm produced the greatest reduction in vascular tissue area. Overall, PBZ effectively regulated vegetative growth and promoted more compact vine architecture through modifications in vascular tissue organisation, suggesting its potential as a strategy for improving canopy management and supporting sustainable passion fruit production.

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