Plastics vs. chemicals as plant growth regulators - Botany

USA Today (Society for the Advancement of Education), June, 2003

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 than plants grown under clear film, which is used as a control standard to compare effects of the colored film. The results are comparable to plants treated with chemical growth regulators."

The scientists also are testing the polyethylene film to determine if it degrades faster in hot regions. "One of the problems we've encountered has been a short film life," Wilson points out. "The dyes start to degrade after one year, so research is being conducted to increase the stability of the dyes." She says the only other difficulty involves delayed flowering time for certain species. "Because photo-selective film has different effects on certain species, growers may need to group plants accordingly in the greenhouse setting."

In addition to ornamentals, the colored films have been used on food plants such as bell peppers, tomatoes, and watermelons. "The potential applications are extensive and exciting. Once the kinks are worked out, plant growth regulation without chemicals will be the future of the industry," she predicts.