# Plants do math - here's how they do it

By James Maynard , Jun 23, 2013 08:05 PM EDT
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Plants do complex arithmetic to prevent them from starving through the night, according to a new study. This is the first time ever that such a degree of mathematics has ever been observed in nature without the use of a brain.

When the sun is set, plants can no longer produce sugars to fuel their biological needs. Therefore, they exist on starches, which are long chains of sugar molecules which can be easily broken apart.

What researchers have just recently discovered is that in order to ration their starch supplies through the night, plants perform division. Plants are able to determine how much starch they have in reserve and divide that number by the remaining hours until dawn. Even more remarkably, they can modify their usage throughout the night.

"The calculations are precise so that plants prevent starvation but also make the most efficient use of their food. 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," Alison Smith, a metabolic biologist who worked on the study, said.

A member of the mustard family named Arabidopsis was studied by researchers from the John Innes Centre in Norwich, England. First, they measure the usage of starch reserves by the plants through the night. They found that the plants used up about 95 percent of their stores each night.

When they then altered the length of the night, the plants adapted by changing the rate at which they processed the starch reserves. If darkness arrived early, so that initial reserves were lowered, the plants responded by lowering the rate of consumption. When they shone light in in the middle of the night on the plants, they were able to recalculate their optimum consumption rate.

"This is the first concrete example in a fundamental biological process of such a sophisticated arithmetic calculation," Martin Howard of the John Innes Centre (JIC) said.

Through mathematical modeling, Smith and Howard proposed that the division might be carried out through the concentrations of two unknown molecules. They deemed these "S," whose levels are dependent on starch content, and "T" which would have a time dependent concentration. The "S" molecule would encourage starch consumption, while "T" would inhibit usage. The two acting together could produce a chemical method of calculating the result of S/T.

During daylight hours, starch is created from carbon dioxide energized by radiation from the Sun, and the starch reserves are replenished for the following night.

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