Water Relations of Leaves of `Sonia' Rose Plants Grown in Soilless Greenhouse Conditions
Rose plants (Rosa hybrids cv. Sonia) were grown in rockwool in two heated greenhouses: one with relative humidity (RH) control (RH >70%) provided by high-pressure mist, the other protected against overheating using a movable screen without RH control. Two electrical conductivity (EC) rates were applied: high (EC of drainage water ≈ 3.8 mS·cm-1) and low (EC of drainage water ≈1.8 mS·cm-1). Under these conditions, water deficit in plants was due mainly to climate, and not to EC. The relative water content of sample leaves picked at noon (RWCnoon) was one to two percentage points higher in the greenhouse with RH control and dropped by 6% to 7% in summer. RWCnoon was unaffected by differences in EC. The average elastic modulus (E) and the relative water content threshold for turgor loss (RWC0) were reduced in the greenhouse with RH control. ϵ was increased in the high EC treatment, but RWC0 remained unaffected.