Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/12/2008
Publication Date: 6/1/2008
Citation: Burnett, S.E., Zhang, D., Stack, L.B., He, Z. 2008. Effects of Phosphorus on Morphology and Foliar Nutrient Concentrations of Hydroponically Grown Scaevola aemula R. Br. ‘Whirlwind Blue’. HortScience. 43(3):902-905. Interpretive Summary: Fan flower is a popular plant for use in hanging baskets and is thus commercially important for many greenhouse growers. As fan flower may develop P toxicity symptoms at lower applied P rates than many species, it is becoming increasingly important to provide growers with specific, accurate recommendations for P concentrations for this horticultural crop. The primary objective of this research was to determine how fan flower morphology is impacted by various P concentrations under a constant pH. We observed that fan flowers fertilized with P concentrations above 20 mg P per liter exhibited some symptoms of phosphorus toxicity. Plants grown in 40-60 mg P per liter had minimal to no chlorosis, but did exhibit reduced shoot and root growth. Leaf chlorosis was observed in plants grown in 60-80 mg P per liter. We concluded that due to rapid accumulation of P in fan flower foliage and subsequent reductions in flower number and shoot elongation, fan flower should be fertilized with no more than 20 mg P per liter.
Technical Abstract: In commercial greenhouses, fan flower ‘Whirlwind Blue’ (Scaevola aemula R. Br.) plants appear sensitive to phosphorus rates typically applied to other floricultural crops. In order to quantify this response, fan flower plants were grown in Hoagland solutions containing 0, 20, 40, 60, or 80 mg P/L. Plants fertilized with either the highest (80 mg P/L) or lowest (0 mg P/L) P concentrations had significantly shorter stems and smaller shoot dry masses and leaf areas than plants fertilized with 20-60 mg P/L. Low or high P concentrations negatively impacted flower development; fan flower fertilized with 0, 60, or 80 mg P/L had fewer flowering branches and flowers compared to plants fertilized with 20-40 mg P/L. Plants receiving no P had longer roots than those receiving any P and had greater root dry mass than plants receiving all other P concentrations except 20 mg P/L. Foliar nutrient analysis indicated that although P treatments significantly impacted foliar concentrations of at least some essential macro- and micronutrients, all essential elements were within or near recommended ranges except P. Foliar P concentrations exceeded 1% in fan flower that received even the lowest concentration of supplemental P, but leaf chlorosis was only observed in plants grown in 60-80 mg P/L solution. Due to rapid accumulation of P in fan flower foliage and subsequent reductions in flower number and shoot elongation, fan flower should be fertilized with no more than 20 mg P/L.