ETHEPHON (2-CHLOROETHYLPHOSPHONIC ACID) EFFECTS ON SCENEDESMUS QUADRICAUDA (CHLOROPHYCEAE)1,2

Growth of Scenedesmus quadricauda (Turp.) Bréb. was significantly increased when the cultures were grown in Ethephon 68–241 (2-chloroethylphosphonic acid) at concentrations of 0.001–1.0 μg · ml^?1. At 0.1 μg · ml^?1, Ethephon caused a significant increase in RNA levels on a dry weight basis. Total protein and DNA levels increased but not significantly. These data indicate that ethylene, the decomposition product of Ethephon at physiological pH, has some effect on the metabolism of algae.