Humans do math or at least some humans can do so.
New research shows that to prevent starvation at night,
plants perform accurate arithmetic division. The calculation allows them to use up their
starch reserves at a constant rate so that they run out almost precisely at dawn.
Plants feed themselves during the day by
using energy from the sun to convert carbon dioxide into sugars and starch.
Once the sun has set, they must depend on a store of starch to prevent
starvation.
In research to be published shortly in the open access
journal eLife, Professors Martin Howard and Alison Smith, scientists at the
John Innes Centre show that plants make precise adjustments to their rate of
starch consumption. These adjustments
ensure that the starch store lasts until dawn even if the night comes
unexpectedly early or the size of the starch store varies.
Starch is a carbohydrate consisting of a large number of
glucose units joined by glycosidic bonds. This polysaccharide is produced by
all green plants as an energy store. It is the most common carbohydrate in the
human diet and is contained in large amounts in such staple foods as potatoes,
wheat, maize (corn), rice, and cassava.
In photosynthesis, plants use light energy to produce
glucose from carbon dioxide. The glucose
is stored mainly in the form of starch granules, in plastids such as
chloroplasts and especially amyloplasts. Toward the end of the growing season,
starch accumulates in twigs of trees near the buds. Fruit, seeds, rhizomes, and tubers store
starch to prepare for the next growing season.
The John Innes Centre scientists show that to adjust their
starch consumption so precisely they must be performing a mathematical
calculation — arithmetic division.
"The capacity to perform arithmetic calculation is
vital for plant growth and productivity," said metabolic biologist
Professor Alison Smith. "Understanding how plants continue to grow in the
dark could help unlock new ways to boost crop yield."
During the night, mechanisms inside the leaf measure the
size of the starch store and estimate the length of time until dawn.
Information about time comes from an internal clock, similar to our own body
clock. The size of the starch store is then divided by the length of time until
dawn to set the correct rate of starch consumption, so that, by dawn, around
95% of starch is used up.
"If the starch store is used too fast, plants will
starve and stop growing during the night. If the store is used too slowly, some
of it will be wasted," according to Prof Smith.
The scientists used mathematical modelling to investigate
how such a division calculation can be carried out inside a plant. They
proposed that information about the size of the starch store and the time until
dawn is encoded in the concentrations of two kinds of molecules (called S for
starch and T for time).If the S molecules stimulate starch consumption, while the T molecules prevent this from happening, then the rate of starch consumption is set by the ratio of S molecules to T molecules, in other words S divided by T - so the plants are doing maths!!
plants growing and doing maths
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