But what about plants? Their food supply is limited and can be variable from day-to-day (for example, due to cloud cover), season to season, and, from generation to generation (as seeds can root in less than optimal locations). How come plants don't get fat.... or whatever the plant-y equivalent is?
That is to say, how do they regulate their energy? Do they have strong willpower or what? Is their energy regulated by biochemical process? Could it be 'plant maths'?
- During the night, mechanisms inside the leaf measure the size of the starch store. Information about time comes from an internal clock, similar to the human body clock.
The researchers proposed that the process is mediated by the concentrations of two kinds of molecules called "S" for starch and "T" for time. If the S molecules stimulate starch breakdown, 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.
"This is the first concrete example in biology of such a sophisticated arithmetic calculation," said mathematical modeller Prof Martin Howard, of the John Innes Centre.
The scientists think similar mechanisms may operate in animals such as birds to control fat reserves during migration over long distances, or when they are deprived of food when incubating eggs.