Plastics vs. chemicals as plant growth regulators.

• Position: Botany

To help commercial nurseries keep plants uniform in size, botanists at the University of Florida, Gainesville, are testing colored plastic films that filter out growth-promoting light waves. Sandy Wilson, an assistant professor of environmental horticulture with the Institute of Food and Agricultural Sciences, says the photo-selective plastic film in her current experiment filters out farred light, which is responsible for stem elongation in plants. "When grown in a greenhouse covered with photo-selective film, plants respond to subtle changes in the amount of far-red light they receive" she notes. "The goal is to inhibit stem elongation without sacrificing plant quality."

The horticulture industry prefers uniform plant size because it speeds plant establishment in the field and makes it easier to pack and ship mature plants. Traditionally, chemicals have been used to control plant height, but, because of increasing environmental concerns, researchers are seeking other methods to accomplish this.

Wilson has been testing the new film on subtropical annuals and perennials at the university's Indian River Research and Education Center, Fort Pierce, where she has obtained favorable results. "Most plants grown under the far-red light absorbing film are about 25% shorter...