Adaptive responses of miniature rose to cultivation modes and abiotic stresses

The miniature rose-bush architecture may be improved by abiotic stresses applied to plants grown under short cultivation mode, which results in their enhanced robustness, branching and blooming capacity. Miniature rose-bushes of the Meikanrou variety, grown in the annual cycle and submitted to vegetative break during winter (“long” cultivation mode, LCM), developed more solid and branched frame with multiple blooms than those grown in an accelerated 4-month cycle, under constant conditions of light and temperature (“short” cultivation mode, SCM). Plants grown under both cultivation modes displayed significant differences in sugars and amino acids content, pH variations of the vascular sap, as well as modified ATPase proton pumping activity. The main biological question to address was whether abiotic stresses (chemical, mechanical and water), applied under SCM conditions might improve horticultural quality by mimicking those of the LCM plants. Notable cyto-histological modifications were observed in stem vascular tissues of the fourth internode under each of the three abiotic stresses. The chemical stress led to increased syringyl/guaiacyl ratio, and thereby, to cell wall strengthening. The mechanical stress displayed the most pronounced decrease of stem length/diameter ratio, favoring the frame robustness. The most pertinent result concerned the controlled water depletion, which not only appeared able to override the reduced branching under SCM conditions, but also further enhanced it to a level similar to that in plants grown under LCM. The application of the chemical, mechanical and water stresses differentially improved branching, stem fortification and blooming capacity of rose-bushes grown under the SCM conditions, thereby providing promising horticultural applications.