Stimulation of adventitious root formation in rose cuttings by laser wounding

authored by

Raul Javier Morales-Orellana

supervised by

Traud Winkelmann

Abstract

Propagation by cuttings is based on the exploitation of plant plasticity, which enables the formation of adventitious roots for the survival of isolated plant parts. This method has been used for the commercial propagation of plant species such as roses. Several strategies have been considered throughout the years to improve rooting percentages using stem cuttings. One of these involves the cultivation of cuttings manually wounded along the stem. The physiological reasons for a root stimulation by additional wounding remained unclear because of the lack of a reliable and reproducible wounding treatment. The main objective of this dissertation was to investigate the effects of wounded tissue by laser on the propagation of single-leaf rose cuttings. The present research was conducted by establishing a tissue-specific laser wounding protocol regarding cutting diameter and energy density. Results showed a stimulating rooting response associated with the exposure of the sclerenchyma layer, particularly when the wound was located below the axillary bud. The induction of wound-induced vascular tissue and adventitious root formation was evaluated by modifying the laser pattern dimension, expressed as the ratio area to perimeter (A/P ratio). Laser-treated cuttings showed a drastic development of new vascular tissue and cambium growth directly in laser- wounded zones, along with an increase in the rooting rate without the addition of exogenous phytohormones. A significant positive correlation was observed between the development of wound-induced phloem growth and rooting percentage. Additionally, rooting percentage was significantly correlated with a growth reduction in the A/P ratio. The study of the biochemical response during the first days of treatment determined that laser treatment of cuttings triggered changes on the stress response (jasmonic and abscisic acid) and a rise in auxin-amino conjugates four days later. A temporal increase in cytokinins (zeatin ribosides) along with a significant increase in root formation was observed specifically when the laser wound was on the leaf-bud side of the cutting. Laser wounds reduced starch content in the wounded sections at the end of the evaluation period, as well as sucrose content, regardless of wound position. The results of this study showed that precise and proper laser wounding, in terms of dimension (perimeter/area), depth, position relative to the leaf and axillary bud, plays a crucial role in stimulating root formation. Laser-wounded tissue triggered remarkable changes in stem morphology and a complex modification in the dynamics of phytohormone profiles and carbohydrate distribution during adventitious root formation. This remarks the potential of laser technology to improve the propagation process via cuttings.

Organisation(s)

Section Reproduction and Development

Type

Doctoral thesis

No. of pages

115

Publication date

08.04.2025

Publication status

Published

Electronic version(s)

https://doi.org/10.15488/18795 (Access: Open)