2017 ASHS Annual Conference

Silicon (Si) is a plant-beneficial element that can alleviate the effects of abiotic and biotic stress. Plants are typically classified as Si accumulators or non-accumulators based on foliar Si concentrations (≥ 1% Si on a dry weight basis for accumulators). Based on this definition, most greenhouse-grown ornamentals are classified as non-accumulators. However, plants that accumulate low foliar Si concentrations may still accumulate high Si concentrations in other tissues, which could have implications for disease management. Additionally, screening cultivars for variability in Si accumulation has not been investigated for many species. Therefore, the objective of this study was to assess cultivar variability in Si accumulation and distribution in petunia, a low Si accumulator. Rooted cuttings of eight cultivars (‘Supertunia Black Cherry’, ‘Supertunia Limoncello’, ‘Supertunia Priscilla’, ‘Supertunia Raspberry Blast’, ‘Supertunia Royal Velvet’, ‘Supertunia Sangria Charm’, ‘Supertunia Vista Silverberry’, and ‘Supertunia White Improved’) were transplanted into 11.5-cm pots filled with a peat-based soilless substrate (LB-2). Greenhouse conditions were maintained at 22 °C day/18 °C night, with a 14 hour photoperiod and supplemental irradiance from high-pressure sodium lamps when ambient irradiance was less than 300 µmol∙m^-2∙s^-1 photosynthetically active radiation. Plants were fertigated as needed with a base nutrient solution of 20N-4.4P-16.6K at a concentration of 150 mg∙L^-1 N. The nutrient solution was amended with either potassium sulfate (0 mM Si) or potassium silicate (2 mM Si) to balance potassium application rates between treatments. Plants were arranged in a completely randomized design, with 10 pots per treatment combination. Petunias were harvested approximately 10 weeks after transplant and separated into roots, stems, leaves, and flowers. Silicon supplementation increased leaf dry mass (5.10 vs. 5.33 g for 0 and 2 mM Si, respectively), but did not affect total dry mass (14.20 vs. 14.14 g for 0 and 2 mM Si, respectively). In plants receiving Si supplementation, mean leaf Si across cultivars ranged between 1248 and 2732 mg∙kg^-1, stem Si ranged between 195 and 654 mg∙kg^-1, flower Si ranged between 253 and 1383 mg∙kg^-1, and root Si ranged between 4018 and 10,457 mg∙kg^-1. The distribution of accumulated Si varied between cultivar, and in Si-supplemented plants, it ranged from 63.5% to 68.2% in leaves, 10.5% to 20.9% in roots, 9.4% to 17.7% in stems, and 1.6% to 9.6% in flowers.