Stomatal conductivity and osmotic adjustment during acclimation to multiple cycles of drought stress in potted miniature rose (Rosa × hybrida)

Summary Reduced water availability during the production of potted miniature roses improves water use efficiency, tolerance to subsequent drought stress and improves post-production performance. However, the physiological response of roses to reduced water availability treatments is not well understood. To explain why a change in production treatment can improve drought stress tolerance, two cultivars of potted miniature roses, Apollo Parade and Charming Paradet were produced with reduced water availability. The plants were exposed to repeated stress and recovery cycles from second cut to flowering. Each of the three 14.d stress cycles included 10.d of reduced water availability and 4.d of recovery, where plants were watered as control plants. During production detailed evaluations were taken on water consumption, water use efficiency, soil and leaf water potential, stomatal conductivity and leaf osmotic potential. The greatest responses occurred following the first exposure to drought. This first exposure to drought had a conditioning effect on the plants which improved their tolerance to subsequent exposure to drought. The two cultivars used different mechanisms to respond to drought in that Apollo utilized osmotic adjustment while Charming modified stomatal closure.