Circadian Rhythms of Plants

Scientists have found that the 24-hour circadian rhythms that guide animal behavior also exist in plants. Research at the Agricultural Research Service’s Vegetable Laboratory shows that a biological clock located in the nuclei of plant cells goes off every morning to prepare plants for their various activities, according to an ARS Web site article by David Elstein.

ARS plant physiologist Autar K. Mattoo has found a few reasons why these clocks go off at precise times and has studied a specific enzyme that modifies the protein known as D1, a critical element in the photosynthesis process, the Web site article says.

Binding phosphorous to D1 at a specific threshold provides a plant with a biotiming signal that tells it to adjust its metabolism to face the onset of the day’s brightest light. The plant also puts on “sunscreen” to protect itself from ultraviolet-B radiation damage, according to the article.

Experiments have found that this biological clock almost always goes off a few hours before noon. Concentrations of triazine and urea-type herbicides, such as atrazine and diuron can block the accumulation of phosphorous on D1.

Mattoo and fellow researchers and students were the first scientists to determine the whole life cycle of the D1 protein after 22 years of collaborative research.

For more information, visit http://www.ars.usda.gov/is/pr/2003/030402.htm

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