Biological Clocks "Wake Up"
Plants By David
Elstein
April 2, 2003
Animal behavior has previously been shown to be shaped by
24-hour circadian rhythms that govern biological processes. Now scientists have
found that these "biological clocks" exist in plants as well. Research at the
Agricultural Research Service's
Vegetable Laboratory in
Beltsville, Md., has shown that a biological clock located in the nuclei of
plant cells goes off every morning to prepare plants for their various
activities.
"Circadian" is a Latin word meaning "about a day." Humans also
have these rhythmic "clocks." Jet lag is an example of a person's biological
clock being out of sync with the actual time of day.
ARS plant physiologist
Autar K. Mattoo has
found a few reasons why these inbuilt clocks go off every day in plants at
precise times. He has spent considerable time specifically studying the one
that controls an enzyme that modifies the protein known as D1, a critical
element in the photosynthesis process.
Binding phosphorus to D1 at a specific threshold provides a
plant with a bio-timing 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 (UV-B) radiation damage.
Experiments were conducted at different times of the year and in
different climates, but the theory that the "alarm" goes off a few hours before
noon almost always proved true. One thing that can block the accumulation of
phosphorus on D1 is the concentration of triazine and urea-type herbicides,
such as atrazine and diuron.
Mattoo worked on this project with researchers and students from
the United States and Israel. As a result of their 22 years of collaborative
research, these scientists were the first to determine the whole life cycle of
the D1 protein.
More
information about Mattoo's research can be found in the April issue of
Agricultural Research magazine.
ARS is the
U.S. Department of Agriculture's chief
scientific research agency. |
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