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.
