Insight on plant growth offered

CHICAGO – How do flowers know to bend toward the sun, plant shoots to grow up, roots to grow down and strawberry seeds to grow fruit?

Figuring out the chemical and genetic steps that command plant cells to grow or divide in response to light or gravity has remainded a puzzle.

Now scientists are abuzz over a solution reported in Wednesday’s British journal Nature by researchers at Indiana University led by Mark Estelle and by Ottoline Leyser at the University of York, England, working independently. They found that the hormone auxin, released with exposure to the sun or pull of gravity, combines with a protein called TIR1 to activate a plant’s genes.

As the discovery opens a new understanding of how plants grow, it could lead to improved crop yields and, perhaps, strawberries as big as softballs.

Charles Darwin speculated about the existence of a plant growth hormone in his 1880 book “The Power of Movement in Plants.” But even after scientists in the Netherlands discovered auxin (derived from the Greek word auxein, to grow) in the mid-1920s, no one could figure out how exactly it triggered plant growth.

Estelle has tried to solve that for 20 years. He succeeded by studying gene mutations in a plant called Arabidopsis thaliana. Scientists identified the genes in Arabidopsis, related to broccoli, cauliflower and similar plants.

Estelle and others say the new knowledge could make food more abundant and nutritious for people around the world. That possibility is likely to increase concern among opponents of genetically modified foods, who worry that manipulating plant genes may become more widespread.

“Plant growth is a very complicated process,” Estelle said. “We’ve made a big advance in terms of understanding how plants grow, but it’s definitely not the whole story.”