Investigation of two possible modes of action of the inert dye aquashade^® on hydrilla

Abstract

The response of the submersed plant Hydrilla verticillata (Royle) in well water solutions of the inert dye Aquashade^® was measured. Growth rate was measured as increase in wet weight following two weeks in a phytotron room at 125 μE/m²/sec. It was found that plants treated with 3 ppm Aquashade^® grew 30.8% ± 9.9% compared to plants without Aquashade^® which grew 62.0% ± 18%. The two mechanisms of action which were investigated were shading and photodynamic action. A plot of percent growth versus concentration of Aquashade^® showed an exponential decrease owing to shading. Available data indicate that the effect of shading is the major, if not exclusive, mode of action affecting the growth of hydrilla.

Key words:

• Hydrilla verticllata
• physiological response
• Aquashade^®
• photodynamic action
• shading