It has been known for some time that the plant hormone abscisic acid is activated in plants under drought conditions by closing the stomata or leaf pores. Steve Neill at the University of the West of England-Bristol, United Kingdom, has discovered that the hormone acts by encouraging the cells that surround the stomata to manufacture nitric oxide that in turn triggers the closure of the stomata. The exact same result is obtained using Viagra. In humans the ‘extra’ dose of nitric oxide relaxes the muscles of blood vessels. The discovery could allow plant breeders to engineer drought resistant plants and the chemical industry could create sprays that stimulate plants to shut down their stomata during periods of drought. Plant Physiology Vol 128, P13.