So-called deepwater rice varieties have a special ability: when the going gets tough, the rice gets growing. The stems elongate rapidly as the paddy floods, keeping the top of the plant above the water, even to flooding depths of 10 feet or more. The elongated, hollow stems act as a snorkel of sorts, allowing gas exchange between the plant tissues and the atmosphere.

This kind of rice is useful in areas where the flooding of paddies is difficult to control. But deepwater varieties don’t yield as much rice as high-yield varieties.

Now Yoko Hattori of Nagoya University in Japan and colleagues have determined the genetic basis of this fast-growing ability. Deepwater rice, they report in Nature, has two genes, which they named SNORKEL1 and SNORKEL2, that get kicked into high gear when the plant is under water.

Ordinarily, ethylene, a gas produced by the plant that acts as a hormone, diffuses out of the plant tissues into the air. But ethylene diffuses much more slowly through water, so when the plant is submerged, the gas accumulates in the plant. The researchers found that this accumulation induces the expression of the genes, resulting in increased production of another hormone, gibberillin, that causes the rapid elongation of the stem.

The researchers suggest that now it may be possible to breed the rapid-elongation trait into high-yield rice varieties. This would enable farmers to produce more rice in areas with frequent and unpredictable flooding.

Published: August 21, 2009 NY Times