The sugary drops that form on the edges of wounds in a particular plant species have been identified as nectar, which attracts the enemies of leaf-eating pests.

Credit: Tobias Lortzing

Plants usually heal wounds quickly, but injuries to the bittersweet nightshade (Solanum dulcamara) do not close fully and produce a sugary secretion (pictured). Anke Steppuhn at the Free University of Berlin and her collaborators conducted greenhouse experiments and found that the droplets attracted ants that defended the plant against two herbivorous pests: slugs and flea-beetle larvae.

Other plants produce nectar in specialized organs called nectaries, and the nightshade's organ-free way of making it could represent an evolutionary origin for these organs, the authors suggest.

Nature Plants http://dx.doi.org/10.1038/nplants.2016.56 (2016)