The plastic, they hope, could be harnessed for packaging and containers and rot quickly after it is thrown away -- unlike many plastics today, which are derived from petroleum and sometimes take decades to biodegrade.

The scientists, with the US biotechnology giant Monsanto, engineered thale cress and oil-seed rape, manipulating their production of amino acids and fatty acid in order to produce the plastic, which is called PHBV.

So far, production of PHBV amounts to around three percent of the plant's dry weight, but this low figure should be boosted with further effort, they said.

"This was a considerable feat of genetic engineering," Nature Biotechnology said.

"Ultimately, if the enhancements in yield can be achieved, plants could one day become remarkably efficient biological factories, producing oils, plastics and animal feed in one crop."

Researchers have long been interested in plastic production from natural sources.

PHBV can already be produced by bacteria, but the process is costly because it requires the addition of a source of carbon, such as glucose, which first has to be extracted from crops like corn.

As a result, plastics made by a bacterial process are five times more expensive than plastics made by conventional process.

Plants are generally considered a better option than bacteria, because they are already loaded with carbon, drawn from the atmosphere.

However, the result has traditionally been poor, because plant plastic lacks a useful strand called a monomer which makes the substance strong and flexible.

The study is published in the October issue of Nature Biotechnology. Thirteen researchers took part in the project, the study of which was authored by Kenneth Gruys of Monsanto Co.