Greenhouse Rose Yield and Ion Accumulation Responses to Salt Stress as Modulated by Rootstock Selection

Greenhouse rose (Rosa x spp. L.) production is facing the use of poor-quality irrigation waters and regulatory pressures to recycle runoff and drainage effluents. Two experiments were conducted to evaluate the yield and quality and ion accumulation responses of roses grafted on various rootstocks to increasing salinity stress. In Expt. 1, the scion 'Bridal White' grafted on 'Manetti', R. odorata (Andr.), 'Natal Briar', and 'Dr. Huey' were irrigated over four flowering cycles with complete nutrient solutions supplemented with NaCl at 0, 5, and 30 mm. In Expt. 2, plants of 'Red France' on 'Manetti' and 'Natal Briar' were irrigated over six flowering cycles with complete nutrient solutions supplemented with NaCl + CaCl2 (2:1 m ratio) at 0, 1.5, 3, 6, 12, and 24 mm. Salt concentration increases significantly and negatively affected the biomass, cut flower production, and foliage quality of the roses in both experiments, but the responses were modulated by rootstock selection. 'Manetti' plants in general sustained better absolute and relative biomass and flower yields, accumulated less Na+ and Cl- in its tissues, and showed less toxicity symptoms with increasing salinity than the others. 'Natal Briar' also had similar absolute productivity responses as 'Manetti' but were afflicted by, a significantly different mineral nutrient profile, including higher accumulations and toxicities with Na+ and Cl- that led to lower foliage visual ratings. Conversely, the relative yields of plants on 'Dr. Huey' and R. odorata were similarly reduced by increasing salinity, but the former had lower Na+ and Cl- concentrations in its tissues and better visual scores than the latter, which fared as the worst. A combined analysis of the results suggests that on a productivity basis (biomass and flower yields), greenhouse roses could withstand overall maximum electrical conductivities (i.e., osmotic effects) of applied fertigation solutions of 3.0 +/- 0.5 dS.m(-1). On the other hand, and considering the aesthetic responses (visual scores) of on-plant and harvested foliage (cut flower shoots), greenhouse rose tolerance to applied Na+ and Cl- concentrations (ion-specific effects) could range up to 10 +/- 2 mm.