Key plant hormone regulated by internal clock: study

By Christopher Doering

WASHINGTON (Reuters) - Scientists may be able to better understand how plants respond to changes and environmental stresses, now that researchers have discovered a link between a plant's internal time-keeper, called a circadian clock, and a hormone that is key to its survival.

Researchers at the University of California-Davis found that a plant's sensitivity to the hormone auxin varied depending on the time of day, with the plant most susceptible at night.

Auxin is vital to a plant's longevity. It helps regulate a plant's growth and development, all the while aiding responses to changes in light, gravity, and water. It also assists the plant in producing fruit and dropping leaves.

The study determined the circadian clock regulates genes that oversee the production, transportation and activation of auxin in the plant.

Michael Covington, lead author of the study, said while only 10 percent of a plant's overall genome is regulated by a circadian clock, a quarter of auxin genes are guided by the clock, which is a 24-hour cycle of physiological processes.

"You already have the clock regulating a lot of different processes, but then you have it regulating auxin, which is essential to the survival of the plant, and bringing the two together is really impressive," Covington said in an interview.

In short, combining the two could allow a farmer to pick when processes happen at the best time of the day to produce a desired outcome such as enhanced growth of the plant.

Almost all living creatures follow circadian clocks, also called circadian rhythms, and plants use them to anticipate daily changes in light and temperature.