Nitric oxide, the chemical at the heart of the drug's success, could work wonders on the food and flower industries, writes Paul Simons

Viagra, the popular drug that helps give men erections, could save plants from even more serious cases of droop. The most startling proof of Viagra's power over plants came from an Israeli scientist, Ya'acov Leshem, at Bar-Ilan University, who was looking at how flowers wither.

He had a hunch that Viagra might work the same magic on plants so he put some into a vase of cut flowers and found they stayed fresh and perky for up to a week longer than usual. Just 2% of the dose needed to treat a bout of male impotence brought a new lease of life to roses, carnations and African daisies.

"The flowers looked much fresher, their colour remained longer, and they were also much more turgid," reported Leshem. No one is suggesting spraying Viagra over plants to stave off wilt: there could be embarrassing side-effects and the cost would be prohibitive, but there might be cheaper and safer alternatives.

When you delve into how Viagra works, you find a remarkably similar chemical story in plants and people. "Plants share the same common denominator as humans - nitric oxide," explains Leshem. This simple, colourless gas has long had a bad reputation for causing traffic pollution, but nitric oxide is now recognised as a powerful hormone in humans. When released from nerve endings, it tells blood vessels to relax and widen to increase blood flow - which is how it gets a phallus erect.

Leshem found that plants naturally give off nitric oxide and, with Ron Wills, from the University of Newcastle in Australia, he fumigated 40 species of flowers, fruit and vegetables with the gas.

"The results were astonishing. Anything from five to 12 hours' treatment with nitric oxide could more than double the shelf life of some species," says Leshem. Strawberries were especially amenable, although thick-skinned fruits such as oranges were untreatable. It also breathed new life into bags of prepared salads, often the saddest items on supermarket shelves.

Nitric oxide could do big things for the food and flower industries. "It is cheap and plentiful, with no identifiable side effects at the very low concentrations we use," Leshem says. However, there is reluctance to using it. Thirty years ago, it was classified as a toxic gas at much higher concentrations. Now we know that plants and animals make their own nitric oxide, attitudes need changing, argues Leshem.

Nitric oxide might also be used to fight crop diseases. "We've discovered that plants use nitric oxide much as animals do, to turn on their immune system," says Daniel Klessig at Rutgers University, New Jersey. Klessig found that at the first hint of infection, a plant launches a nitric oxide attack, telling the cells at the infection site to commit suicide and kill off the invader, then warn the entire plant to defend itself.

The gas also comes to the rescue of plants wilting in drought. Steven Neill, at the University of West England in Bristol, gave plants a whiff of nitric oxide and found they squeezed shut their tiny leaf pores, stopping their water supplies from evaporating. He's now trying out Viagra and expects to boost the nitric oxide effect. "I don't think Viagra will be a panacea for drought plants," he says, "but spraying crops with products that can make nitric oxide might be sensible."

Saving a plant from the droop may not be as sexy as rescuing an erection, but its repercussions could be far more awesome. It has been estimated that 65% of the Earth's water supplies pass through plant stomata at some time. "Global water shortage is going to be a big environmental problem this century, so anything that improves water efficiency in plants is attractive," says Neill. Which just goes to show how Viagra and its nitric oxide buddy give plants a huge lift.