Inhibition of float formation in water hyacinth by gibberellic acid

Abstract

THE water hyacinth (Eichhornia crassipes) is one of the most harmful weeds of tropical and subtropical waterways and lakes. Its reproductive potential is enormous and in favourable conditions it forms dense mats which may cover the surface of a body of water. Such prolific development can obstruct the drainage of farmlands, block hydroelectric installations in dams, hinder navigation and affect fisheries (reviewed in ref. 1). The leaves of free-floating water hyacinths are characterised by a bulbous swelling in a section of the petiole which provides buoyancy. These floats, however, do not develop when the plants are rooted in the soil of muddy shores. In those circumstances the petiole narrows gradually from its base to the leaf blade. We have found that the formation of floats can be inhibited by extremely low concentrations of gibberellic acid (GA₃) in the water. As a consequence of treatment the plants become unstable and partially sink below the surface of the water.