Thursday, April 28

When pests bite, a nightshade plant bleeds ant food

Enlarge (credit: Tobias Lortzing)

Nature is, it’s often said, red in tooth and claw. But sometimes a claw scratches someone’s back in return for a symbiotic scratch of one’s own. Ants provide many examples of such mutually beneficial arrangements. As weird as it sounds, drinking the “blood” of a wounded bittersweet nightshade plant appears to be one of them.

Ants and plants are often good friends (leafcutters aside) because ants prey on insects that munch on the plants. Some plants keep ants on retainer by secreting nectar from special structures (fittingly called “nectaries”) that can be found in various parts of the plant. The acacia tree even goes as far as growing hollow thorns that ants can nest inside when they aren’t dining on the gourmet ant food the tree provides. (Full disclosure: acacias also drug the ants so they can’t live off other food sources. It’s a complicated relationship...) The benefits the tree obtains from its ant security detail apparently outweigh the energetic costs of these lavish gifts.

Something a little more subtle is going on with the bittersweet nightshade plant. A group of researchers led by Tobias Lortzing of the Free University of Berlin noticed that this nightshade bleeds sugary droplets when damaged, rather than quickly closing up its wounds. Seeing ants hit up those droplets for a snack, they wondered whether the plant adapted to call in ant support when herbivores come a-munching.

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