EFFECT OF CONTINUOUS OR DISCONTINUOUS WATER RESTRICTIONS ON THE ARCHITECTURE OF TWO- AND FIVE-MONTHS-OLD GARDEN ROSE (ROSA HYBRIDA 'RADRAZZ')
One of the main criteria for the visual quality of an ornamental plant such as rose bush is its shape, which should be compact and branched. To control both growth and branching, chemical growth regulators are commonly used. However, they have a negative impact on the environment and new environmental-friendly alternatives must be found. Water restrictions are known to reduce plant growth, but their effects on branching are still poorly understood. Rooted cuttings of rose plants (Rosa hybrida Radrazz) were grown in the greenhouse. Irrigation was managed by tensiometers in order to maintain the water potential of the substrate at a constant level (-8 or -26 kPa in Exp. 1) or to activate irrigation at a given level (-10 or -30 kPa in Exp. 2). Plants were submitted either to continuous water restrictions applied from the appearance of the order 1 axis floral bud until the flowering of order 2 (Exp. 1), or to alternations of dehydration-rehumectation of the substrate (discontinuous water restriction) applied from the emergence of order 2 axes until the flowering of order 4 axes (Exp. 2). Both continuous and discontinuous water restrictions reduced the length and diameter of axes that emerged after the beginning of the water restrictions. These reductions in axis length were due to the reduction of the mean metamer length and/or to the reduction of the metamer number per axis. Water restriction tended to decrease branching. Water restriction therefore led to the production of smaller but not always more compact rose bushes. The use of water restriction as an alternative method to chemical growth regulators to control plant shape still requires a specific technical itinerary to increase branching.
Huché-Thélier, L., Morel, P., Le Coz, E., Sintès, G., Guillemain, G. and Crespel, L. (2013). EFFECT OF CONTINUOUS OR DISCONTINUOUS WATER RESTRICTIONS ON THE ARCHITECTURE OF TWO- AND FIVE-MONTHS-OLD GARDEN ROSE (ROSA HYBRIDA 'RADRAZZ'). Acta Hortic. 990, 363-368
Rosa hybrida, irrigation, plant architecture, height and compactness of plant, growth regulator, ornamental plant