Effects of potassium silicate on the growth of miniature rose 'Pinocchio' grown on rockwool and its cut flower quality

The effects of root and foliar applications of potassium silicate on the growth and quality of hydroponically-grown cut flower miniature rose Rosa hybrida 'Pinocchio' were evaluated. In a hydroponic system that uses rockwool slabs as a growing medium, the growth and quality of plants in four treatments, including the control (untreated), root feeding, foliar spray, and root feeding + foliar spray of a 200 mg (.) L-1 potassium silicate solution, were examined. The treatments were laid out in a randomized block design with four replicates per treatment. Four rooted cuttings per treatment started on rockwool cubes were planted on a rockwool slab on Aug. 7, 2000 and grown for 413 days. The mean flower stem length, mean yield by grade, and total yield were significantly greater in the root feeding treatment than in the others; likewise, fresh and dry weights of roots were significantly heavier. Stem diameter, number of branches, dry matter, and shoot fresh and dry weights significantly increased in the root feeding + foliar spray plot as compared to the control. Stem flexibility, measured as the modulus of elasticity was greatest in the root feeding + foliar spray treatment. Photomicrographs taken with a scanning electron microscope showed the formation of a film of glass on the leaf surface in the foliar spray treatment. From these results, we concluded that the applications of potassium silicate proved to have beneficial effects on the growth and quality of cut flower miniature rose 'Pinocchio' in the rockwool culture system.