By Mark Kinver
Science and environment reporter, BBC News
There are an estimated 400,000 species of land plants on the planet
An international team of scientists has agreed on a standard "DNA barcode" for plants that will allow botanists to identify species quickly and easily.
They hope the agreement will lead to the formation of a global plant DNA library, which can be shared by the scientific community.
The barcodes are expected to have a number of uses, including identifying illegal trade in endangered species.
The findings appear in the Proceedings of the National Academy of Sciences.
"Identification is important," said lead author Dr Peter Hollingsworth, head of genetics and conservation at the Royal Botanic Garden, Edinburgh, Scotland.
"It is the link between a given plant and the accumulated information available for that species.
"It is not possible to know whether a plant is common or rare, poisonous or edible, being traded legally or illegally, unless it can be identified."
Co-author Robyn Cowan, a conservation geneticist at Royal Botanic Gardens, Kew, said the development would allow larger areas to be surveyed more quickly.
The "barcode" will allow plants to be identified from tiny fragment
"We are short of botanists and their expertise in a lot of places around the world," she told BBC News.
"This is one way that we will be able to increase our information and understanding of biodiversity and where things are growing around the world."
Samples could now be sent back to laboratories to be processed and identified, she explained, cutting out the need for a specialist botanist to be on location.
Ms Cowan said the new method would also help to put the necessary conservation measures in place quickly, to save endangered species.
"And there are also more applied uses; in forensics, for example," she said.
"We have also done a little bit of preliminary work on Chinese herbal medicines. We have been checking that people are getting what they should be getting in terms of medication and active ingredients.
"One thing that is really good about this process is that you can identify plants from different life stages or just fragments of plants.
"For example, if you are looking at trade in endangered species and you have things that are not flowering, or are just seedlings, it can be incredibly difficult to positively identify the plants."
Ms Cowan explained why it had been more of a challenge to find a suitable DNA barcode for plants than for animals, which had been in use since 2003.
"The DNA in land plants behaves, in some ways, quite differently to DNA in animals, so we were not able to use the same [marker]," she said.
"We had to search for the best solution because a barcode needs certain characteristics.
Barcodes will be used to catalogue the world's 100,000 tree species
"It needs to be technologically easy to deal with; it needs to be readily obtainable from degraded material (very old samples or fragments); and it needs to be variable enough between species to be able to separate them but not too variable within species."
The team assessed seven potential "barcodes", testing them on a common set of samples. Eventually, they chose two regions of DNA to form the plant barcode."
"The conclusion we have come to will give us a good basic barcode to use."
The four-year project was carried out by the Consortium for the Barcode of Life (CBOL) Plant Working Group, which consists of 52 scientists from 10 nations.
David Schindel, executive secretary of CBOL, applauded the breakthrough: "The selection of standard barcode regions has been a slow and difficult process because of the complex nature of plant genetics."
Dr Schindel added that the development would "enable plant barcoding to accelerate rapidly".
One use will be to build a DNA database for the world's 100,000 tree species, many of which are deemed to be of either conservational or economic importance.