Extrafloral nectaries: how plants attract bodyguards to fight against plant eating insects

Do you think plants only produce nectar in flowers to attract pollinators and to help with pollination? Read on as plants have evolved more uses for nectar than you might expect.

Extrafloral nectaries on a cherry leaf stalk

Many plants (for example cherry (Prunus), willow (Salix) and passionflower (Passiflora)) have nectar-secreting plant glands which develop outside flowers and are not involved in pollination. These glands are called extrafloral nectaries.

Extrafloral nectaries can occur on leaves, plant stalks (petioles), plants stems, fruits and virtually any other above-ground plant part. Extrafloral nectaries can look quite variable in different plant species and can range from single-celled trichomes (plant hairs) to complex cup-like structures.

The nectar produced in extrafloral nectaries is used to attract predatory insects (such as ants or wasps) which will not only drink the nectar but will eat plant-eating insects as well. Thereby the plant recruits its own personal army of bodyguards which are fed with nectar and in return defend the plant against harmful insects.

Extrafloral nectaries are used to attract predatory insects

 
So next time you see a cherry tree have a look for the extrafloral nectaries (located on the leaf stalk and very obvious); maybe you can even see some ants or wasps drinking the nectar.