Involvement of the auxin–cytokinin homeostasis in adventitious root formation of rose cuttings as affected by their nodal position in the stock plant

Abstract

Main conclusion Enhanced levels of indole-3-acetic and raised auxin to cytokinin ratios in the stem base contribute to the positive acropetal gradient in rooting capacity of leafy single-node stem cuttings of rose. Abstract Cuttings excised from different nodal positions in stock plants can differ in subsequent adventitious root formation. We investigated the involvement of the auxin–cytokinin balance in position-affected rooting of Rosa hybrida. Leafy single-node stem cuttings of two rose cultivars were excised from top versus bottom positions. Concentrations of IAA and cytokinins were monitored in the bud region and the stem base during 8 days after planting using chromatography–MS/MS technology. The effects of nodal position and external supply of indole-butyric acid on rooting were analyzed. Most cytokinins increased particularly in the bud region and peaked at day two before the bud break was recorded. IAA increased in both tissues between day one and day eight. Top versus bottom cuttings revealed higher levels of isopentenyladenosine (IPR) in both tissues as well as higher concentrations of IAA and a higher ratio of IAA to cytokinins particularly in the stem base. The dynamic of hormones and correlation analysis indicated that the higher IPR contributed to the enhanced IAA in the bud region which served as auxin source for the auxin homeostasis in the stem base, where IAA determined the auxin–cytokinin balance. Bottom versus top cuttings produced lower numbers and lengths of roots, whereas this deficit was counterbalanced by auxin application. Further considering other studies of rose, it is concluded that cytokinin-, sucrose- and zinc-dependent auxin biosynthesis in the outgrowing buds is an important factor that contributes to the enhanced IAA levels and auxin/cytokinin ratios in the stem base of apical cuttings, promoting root induction.

Biochemical and Physiological Changes during Early Adventitious Root Formation in Chrysanthemum indicum Linné Cuttings

“…The average number of roots, root length, and biomass were higher in the apical segments than in the medium and basal segments. Similar results have been reported for the Rosa hybrid [ 83 ]. In contrast, another report observed no significant difference in rooting rate when the cuttings were collected from different positions along with the donor plants [ 84 ], indicating that the rooting potential of the cutting is significantly affected by the physiological state of the explants used in the experiment.…”

Lighting from Top and Side Enhances Photosynthesis and Plant Performance by Improving Light Usage Efficiency

“…Moreover, the TS lighting resulted in the greatest light efficiency, which further induced well-developed terminal buds and lateral buds, causing higher bio-activities and promoting phytohormone cycles. Meanwhile, the well-developed lateral shoot preferentially receives branch-promoted hormones such as cytokinins transported from the root, thus promoting the quantity and quality of the lateral buds [ 46 , 47 , 48 ]. In addition, according to the nutrition theory that K. Gerber proposed, the well-developed bud cells rapidly grow, vigorously metabolize, and require more nutrients.…”

Side Lighting Enhances Morphophysiology by Inducing More Branching and Flowering in Chrysanthemum Grown in Controlled Environment

“…In addition, it was found that the lateral buds were able to grow when the cytokinin was applied to the inhibited lateral buds, and the apical dominance was relieved. Therefore, an inhibition of the lateral buds occurred, because they did not have enough cytokinins directed toward them [ 61 , 62 , 63 ]. In our study, the chrysanthemum plants grown using the side lighting lacked light from the top and experienced a stunted development of the terminal bud.…”