Response of potted miniature roses (Rosa x hybrida) to reduced water availability during production

The degree of drought tolerance exhibited by a plant is related to its ability to respond to adverse conditions. To determine if it is possible to alter this capacity in potted miniature roses (Rosa x hybrida), plants were produced with reduced water availability during the six weeks prior to flowering. The response of two rose cultivars to a cyclic non lethal water deficit treatment (moderate water deficit with 5 d stress and 5 d recovery) and two long-term steady-state water deficit treatments at 60% (severe water deficit) and 75% (moderate water deficit) water availability, were compared. All plants produced with water deficit were more compact than control plants and the cyclic-grown plants most closely resembled commercially produced plants. Whilst all drought treatments significantly reduced the number of buds at flowering, time to flowering was not influenced by the treatments. Moderately stressed plants maintained leaf numbers but reduced the size of the individual leaves by 20%. In contrast the severely drought stressed plants reduced both leaf number and total leaf area by 40%; consequently individual leaf size was maintained. Total daily water consumption per unit leaf area was reduced only under severe stress. However, all plants grown with reduced water availability significantly reduced dark transpiration rates as a percentage of light transpiration, with the cyclic-grown plants being the most efficient. During recovery the cyclic plants restored stomatal conductance and photosynthesis to rates comparable with control plants. All plants produced with reduced water availability were more efficient in dry-matter production per volume of water consumed as compared with controls. The response of potted miniature roses to steady-state versus cyclic water-deficit treatments is discussed.