MSU Researcher Says Too Much Light May Not be Good for Short-Day Plants
3/3/08
Contact: Sara Long
517-432-1555, ext. 170
EAST LANSING, Mich. -- Greenhouse growers have experienced declining profit margins over the past decade, a situation that has only grown worse with rapidly rising fuel prices. This “perfect storm” has stranded growers in the unenviable position of figuring out how to do more with less.
But now, thanks to research conducted by Ryan Warner, Michigan State University (MSU) assistant professor of horticulture, greenhouse producers may soon be able to reduce their energy bills. Warner’s findings showed that adjusting light levels and day length can reduce by as much as 30 to 40 percent the length of time that plants spend in the greenhouse before flowering.
“The two largest costs associated with producing greenhouse crops are labor and heat, both of which are directly related to the amount of time the crop spends in the greenhouse,” Warner said. “Being able to control the flowering process will enable growers to reduce the time needed for production. By manipulating the amount of day length that plants are exposed to, growers will be able to start growing their spring bedding plant crops later in the season, when outside temperatures are higher.”
Warner noted this will reduce the amount of fuel required for greenhouse heating.
“The earlier that growers need to start growing plants in the winter to make sure plants are at the right maturity stage for early spring planting, the more resources they have to use for heating and light and the greater the expense,” he said.
Michigan is a prominent player in the U.S. greenhouse industry. In 2005, the value of the state’s floriculture industry topped $384 million, and Michigan ranked second in the country in bedding plant production. Warner’s research could contribute to reducing annual energy costs for greenhouse operators, ultimately improving their bottom lines.
Warner’s research used photoperiod manipulation -- changing the amount of time that plants are exposed to light -- to induce several varieties of annual and herbaceous perennial bedding plants to flower earlier in the season, thus reducing the amount of time that plants would need to remain in the greenhouse.
“One of the advantages that greenhouse growers have over those who grow crops outside of a greenhouse environment is that they can manipulate the environment by controlling day length and temperature,” Warner said.
In Michigan, sunlight levels are very low during the winter and early spring. To compensate for low light levels, growers expose most young plants, or “plugs,” to 14 to 18 hours of artificial lighting per day.
Many spring bedding plants, however, are short-day plants. Warner’s research found that growers could reduce the time to flowering by five weeks by exposing these plants to nine-hour light periods after the first true leaf unfolded. In addition, he found that some long-day plants, such as petunia and black-eyed Susan, flower much earlier if exposed to longer periods of light at a young age.
Even though greenhouse growers could grow their plants on a tighter schedule if they were able to maximize crop production efficiency, Warner warned that plants will not reach their full size if the flowering process is induced too early.
“We learned that we can reduce flowering time by 30 to 40 percent, but this can be a negative result in some cases because the plants will flower too early, when they are too small,” he said. “The goal is to reduce production time without reducing quality.”
Warner received funding from Project GREEEN (Generating Research and Extension to meet Economic and Environmental Needs), Michigan’s plant agriculture initiative at MSU, to conduct his research.
“Project GREEEN is a critical initiative,” he said. “It allows researchers to conduct this type of applied research that can develop practical, useful information that can be immediately applied to the greenhouse industry.”
Founded in 1997, Project GREEEN is a cooperative effort between plant-based commodities and businesses together with the Michigan Agricultural Experiment Station, MSU Extension and the Michigan Department of Agriculture to advance Michigan’s economy through its plant-based agriculture. Its mission is to develop research and educational programs in response to industry needs, ensure and improve food safety, and protect and preserve the quality of the environment.
To learn more about Michigan’s plant agriculture initiative at MSU, visit www.greeen.msu.edu.
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