How Plants 'Clot' After Being Wounded

Tiny blockades

Plasmodesmal Channels

Plasmodesmal Channels

The purple dots in this image are deposits of callose, a substance that plants can use to seal off a wounded part of the plant from the healthy part.University of Delaware

Next time you stop and smell the flowers, consider this: how do plants handle injuries? It's not like they can retreat from a dangerous situation. So what do they do to survive in an inhospitable world?

A paper published today in Nature Plants has at least part of the answer. It turns out that when plants are injured, they can form a barrier kind of like a blood clot, keeping the healthy part of the plant safe by isolating the injured part. The isolation helps in an infection by preventing germs from spreading, but it also helps with mechanical injuries, so that a plant doesn't continue to pour resources like water and nutrients into a doomed cell.

Plasmodesmata are channels within a plant's structure that connect neighboring cells to each other.

"Plants do not have cells that move freely like humans do because plant cells are kind of glued together. So they have to have a different way to communicate and that's these channels," Weier Cui, one of two authors on the paper said.

The researchers found that when a plant was wounded, a material called callose acts as a barrier in those channels, building a wall that few nutrients or signals can pass through. Callose is also used when the plant is infected, walling off the infected part and preventing dangerous microbes or viruses from spreading too far in the organism. Cui and co-author Jung-Youn Lee found that the presence or absence of callose within the plasmodesmata is regulated by two different enzymes, one in response to infection, and one that responded to mechanical stressors, like a tear or puncture.

In both cases, the callose cuts off the injured or infected cell from the rest of the plant, creating a quarantine zone. While the quarantined part of the plant fends for itself, the rest of the plant has a fighting chance.