Should I stay or should I go?

Flowering plants use subtle chemical cues to simultaneously attract and reject visitors, ensuring the best fertilization results, Ian Baldwin and colleagues report in Science.

Plants, for the most part immobile, have had to evolve tricky ways to get others to do their fertilizing dirty work. Flowers, with their bright colours and fresh scents, have had a key role in attracting insects and birds to spread pollen between flowers. Unfortunately, however, these visitors aren’t always there to help -- nectar thieves, for instance, hinder plant procreation by using up valuable plant resources without providing anything in return. So how can plants ensure that visitors come to their flowers (where they can pick up pollen), but then not stay too long (they need to visit other plants too for fertilization to succeed, after all) or hog the nectar?

To examine this question, Ian Baldwin and colleagues manipulated production of benzyl acetone, a floral attractant, and nicotine, a repellent, in Nicotiana attenuata, a tobacco plant. In the absence of benzyl acetone, pollinators such as hummingbirds, visited the flowers much less frequently. In the absence of nicotine, however, nectar thieves, such as moths and carpenter bees, were observed feeding on the flowers more frequently. Moreover, when the plants produced both the attractant and the repellent, as they do in the wild, they produced the most seeds – in other words, had the highest fertilization success.

Using a mix of attracting and rejecting signals, plants seem to have mastered the subtle art of seduction. Whether this explains why it’s best not to call too soon after a first date is still unclear.