When a pollen grain lands on the female reproductive organ of a compatible plant, it forms a pollen tube that grows through this complex structure to deposit male gametes in the ovary. Prado and colleagues report on p. 2707 that nitric oxide (NO) is an important negative regulator of pollen tube growth. Working in vitro with pollen from Easter lilies (Lilium longiflorum), they show that above a critical concentration, an external point source of NO causes transient inhibition of pollen tube growth followed by reorientation of the direction of growth. The researchers provide pharmacological evidence that this response is mediated through a cGMP pathway. Finally, they identify peroxisomes, which are normally excluded from the pollen tube tip, as the organelles that synthesise NO and suggest that endogenous NO production correlates with the regulation of pollen tube growth.