Natures wonders: calling ant defenders (Introduction)

by David Turell @, Monday, April 25, 2016, 19:00 (1328 days ago) @ David Turell

Bittersweet nightshade puts out a sweet nectar to call ants to its defense:

"Calling pest control. When attacked, bittersweet nightshade plants release sugary secretions from their wounds to summon ants that hit back at the assailants.

"Many plants attract predators of herbivores by secreting nectar from specialised glands called extrafloral nectaries.

"But the nightshade, Solanum dulcamara, is the first plant known to do this without any specialised nectar-making structures.

"Anke Steppuhn and colleagues at the Free University of Berlin, Germany, discovered that sweet droplets ooze out from wounds anywhere on the plant when it gets chewed by herbivores. How exactly they make it is unclear, but it could be as simple as having a few sucrose-transporting proteins in the wounded tissue.

"The fluid isn't sap; it is simpler, consisting mostly of water and sucrose. In greenhouse experiments, the secretions attracted three species of ants to patrol the plants.

"We've now observed that the plant, without any structure for secreting nectar, can use this kind of defence - which means that you do not need an organ,” says Steppuhn.


"Plant biologists had been puzzled by the existence of extrafloral nectaries in a wide variety of plants, which suggested that they had evolved independently many times. This seems less surprising if plants can make nectar without specialised organs: it could be a common first step towards the evolution of nectaries outside flowers.

"Steppuhn thinks that if we look more carefully, we'll find more plants that bleed nectar to attract ants. Apart from leafcutter ants, ants generally don't eat plants. So if they are found on one, it's usually because there are sap-sucking insects there that excrete sugar. “If none of those insects are found, we should search those plants for plant-derived nectar that attracts the ants,” she says."

Comment: More than one way to defend oneself.

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