Response of Selected Garden Roses to Drought Stress

A greenhouse study was conducted to evaluate the response of four garden roses (Rosa x hybrid L.), 'RADrazz, 'Belinda's Dream', 'Old Blush', and 'Marie Pavie', to drought stress. Plants grown in containers were subjected to two watering treatments, well-irrigated [water as needed: approximate to 35% substrate moisture content (SMC) at re-watering] and cyclic drought stress (withholding irrigation until plants exhibit incipient wilting: approximate to 10% SMC, then re-watering to field capacity for subsequent dry down). Shoot growth and flower number were reduced in the drought treatment compared with the well-irrigated plants in all cultivars with least reduction in 'RADrazz'. Drought stress reduced root growth in 'Belinda's Dream' and 'Marie Pavie', whereas there was no difference in root growth in 'RADrazz' and 'Old Blush'. Decreased SMC induced reduction in net photosynthetic rate (P-n), stomatal conductance (g(S)), transpiration rate (E), and midday leaf water potential (psi). Leaf water use efficiency (WUE) increased as SMC decreased in all cultivars. However, the relationship between these physiological parameters and SMC differed among the cultivars. At SMC between 10% and 20%, 'RADrazz' had higher P-II, g(S), E, and WUE compared with the other three cultivars. Therefore, 'RADrazz' was the most drought-tolerant during container production among the cultivars investigated. With lower gas exchange rates and greater reduction in flower number at low SMC, 'Marie Pavie' was less drought-tolerant compared with the other three cultivars.