Factors Affecting Foliar Absorption of Nutrients by Selected Landscape and Herbaceous Plants

Plants and solution properties affecting the absorption of double-labeled ⁸⁶Rb ³³P-phosphate, pH 7.2, by chrysanthemum leaves were studied. Leaf age did not affect absorption greatly. Optimum concentration for maximum total absorption and efficiency of absorption of both Rb and P without leaf burn was 20-30 mM Rb phosphate. Urea and several structurally related compounds (acetamide, propionamide and Rb acetate) decreased Rb and P absorption due to formation of salt deposits. Of 18 commercially available surfactants tested at 0.1%, only one significantly increased P absorption and all significantly decreased Rb absorption; many were phytotoxic. Of a variety of 20 different herbaceous ornamental and woody landscape species tested for their efficiency of absorption, P absorption ranged from 0.2-39% and Rb absorption ranged from 0.2-42%; surfactants generally increased the absorption of P and Rb for those species with waxy, pubescent or otherwise hard-to-wet leaves.