Bacteria can 'farm' plants

MONTREAL, May 26 (UPI) -- A group of bacteria uses chemical signals to increase the growth of plants, in effect "farming" the plants for their own advantage, McGill University researchers have discovered.

"We grow plants for our own benefit as farmers and that's what the bacteria are doing," plant science professor Donald Smith told United Press International. "They're making more habitat and a larger food source for themselves by stimulating the plant growth."

The findings may have implications for human agriculture, Smith said, because the chemical signals used by the bacteria also cause increased growth in a wide range of crop plants, from corn to canola and from cotton to cucumbers.

Smith and colleagues made the discovery while studying the symbiotic relationship between soybeans and what are called "nitrogen-fixing" bacteria. The bacteria remove nitrogen from the air for plants to use, and the plants create nodules on their roots in which the bacteria can live.

A young soybean plant releases chemical signals to attract the bacteria, which reply by sending other chemical signals that tell the plant to begin making the nodules. Those bacterial chemicals, called by the unwieldy name lipo-chitooligosaccharides -- or LCOs for short -- also affect the growth of other plants, Smith said.

"It works on quite a range of plants," he told UPI. "We were surprised by that."

Smith said his team has shown applying LCOs to roots, leaves, or seeds of plants caused faster germination, speedier growth, and an increased rate of photosynthesis -- the process by which plants use sunlight to convert carbon dioxide and water into food.

Part of the research is scheduled to be published in September in the Journal of Experimental Botany. Other aspects have been submitted to the journals Planta and Photosynthesis Research, Smith said.

Plant geneticist David Wolyn of the University of Guelph, near Toronto, said Smith's work is a "very interesting finding" that implies some basic similarities across two broad classes of plants -- for instance, the monocotyledons, such as corn, and the dicotyledons, such as soybeans.

The cell division process is central to growth, Wolyn said, and it is possible that the signals causing cell division are so fundamental they are the same in many different types of plants. If so, he said, "it would be logical that applying (LCOs to other plants) would have similar effects in terms of growth and cell division."

Smith said test fields of soybeans, treated with extra doses of LCOs, saw yields increase by 25 per cent. Such a large increase would be unlikely in a farmer's field, he added, but even smaller improvements could be economically important.

He added even small changes -- one or two days -- in the speed with which plants germinate and grow might be valuable, by reducing the time they are vulnerable to diseases and competition from weeds.

(Reported by Michael Smith in Toronto)