It's the day (and night) of the Triffids! Research reveals that plants use complicated calculations to regulate their energy reserves

Plants make food from sunlight, then use constant calculations to ration food use through the night (AFP)

Putting anyone who has woken up at night to polish off the remaining goodies in their fridge to shame, new research shows that plants use maths to stave off hunger until the morning.

During the night, plants calculate how much food they need to save themselves from starvation almost precisely until dawn.

Plants feed in the day using a process called photosynthesis. This harnesses energy from the sun to convert carbon dioxide into sugars and starch. But once the sun sets, they must depend on a store of starch to make it to the morning.

The research was conducted by the John Innes Centre in Norwich, an independent institution specialising in plant science and microbiology. It suggests that the precision with which plants adjust their use of starch shows they are performing a mathematical calculation. Instead of a level of use set at the onset of darkness, plants continuously compute the food they need during the night.

"This is the first concrete example in biology of such a sophisticated arithmetic calculation," said Professor Martin Howard, a mathematical modeller at the centre.

Experiments have shown that even when night comes unexpectedly and a plant's supply of food is gone, or the amount of starch already stored varies, plants are able to make adjustments to the supply until dawn.

Professor Alison Smith, a metabolic biologist at John Innes, said: "The capacity to perform arithmetic calculation is vital for plant growth and productivity. 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."

Researchers discovered that the size of the starch store and the time until dawn is encoded in the concentrations of two kinds of molecules. Plants use the ratio between the two to make a mathematic division.

Supported by the idea that cells can use proteins to store and process information through a network, this research also has potential outside the botanical world.

It could be used to explain how the migrating stint, a small bird, travels for 5,000km and yet retains, upon arrival, enough fat to last half a day. Similarly, male emperor penguins that incubate eggs in anticipation of the female's return only reach a critical level of hunger depletion when their partner is expected back.