Polyphenolic Acid Changes in Stem Cuttings of Rosa Cultivars in Relation to Phenological Stage and Rooting Enhancers

Abstract

Biostimulants and rooting enhancers, i.e., auxins, affect many aspects of plant development. The experiment in this paper focused on the response of single-node rose semi-woody cuttings to rhizogenesis-enhancing preparations based on plant extracts in terms of changes in polyphenolic acid content. The shoots were cut at four stages of flowering development: (i) flower buds closed, (ii) open flower, (iii) immediately after petal shedding, (iv) 7–14 days after petal shedding. The experimental material consisted of six old, once-flowering rose cultivars (‘Duchesse d’Angoulême’, ‘Hurdals’, ‘Maiden’s Blush’, ‘Mousseuse Rouge’, Rosa beggeriana ‘Polstjårnan’, R. helenae ‘Semiplena’). The following rooting-enhancers were applied: commercial powder containing (i) 0.4% indolebutyric acid (IBA) or (ii) 0.2% naphthalene acetic acid (NAA) or commercial plant-extract mixtures named in the experiment, i.e., (iii) Seaweed Preparation, (iv) Humic Preparation, and (v) Plant Preparation, and (vi) the control cuttings, which remained untreated. The level of polyphenolic acids was determined before and after rooting. The content of polyphenolic acids had a tendency to decrease during the period of rhizogenesis for all cultivars and all phenological stages. Changes in polyphenolics were affected by all the rooting enhancers, but the contents of these compounds before and after rooting was not found to unambiguously correlate with either the final rooting percentage or quality of cuttings.