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 abil ity to respond to adverse conditions. To determine if it is possible to alt er this capacity in potted miniature roses (Rosa x hybrida), plants were pr oduced with reduced water availability during the six weeks prior to flower ing. The response of two rose cultivars to a cyclic non lethal water defici t treatment (moderate water deficit with 5 d stress and 5 d recovery) and t wo long-term steady-state water deficit treatments at 60% (severe water def icit) and 75% (moderate water deficit) water availability, were compared. A ll plants produced with water deficit were more compact than control plants and the cyclic-grown plants most closely resembled commercially produced p lants. Whilst all drought treatments significantly reduced the number of bu ds at flowering, time to flowering was not influenced by the treatments. Mo derately stressed plants maintained leaf numbers but reduced the size of th e individual leaves by 20%. In contrast the severely drought stressed plant s reduced both leaf number and total leaf area by 40%; consequently individ ual leaf size was maintained. Total daily water consumption per unit leaf a rea was reduced only under severe stress. However, all plants grown with re duced 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 conduc tance and photosynthesis to rates comparable with control plants. All plant s produced with reduced water availability were more efficient in dry-matte r production per volume of water consumed as compared with controls. The re sponse of potted miniature roses to steady-state versus cyclic water-defici t treatments is discussed.