Plants that Eat Other Plants: Why Parasitic Plants Attack

Scientists have learned a bit more about parasitic plants, which leech nutrients from a host plant. They've found out how these plants evolved the ability to detect and attack their hosts, which may lead to new techniques to control thieving weeds.

There are thousands of parasitic plants species, but the most burdensome for humans are those that destroy crops. Parasite infestations can reduce crop yields by billions of dollars each year.

"In the simplest terms, these are plants that eat other plants," said David Nelson, co-author of the new study, in a news release. "The seeds of some parasite plants, like witchweed for example, can lie dormant in soil for more than a decade, waiting to grow until they detect the presence of a host. We wanted to understand how the parasites know other plants are nearby so we could develop new ways of combating them."

As plant roots grow, they release hormones called strigolactones into the soil. This is a signal that normally helps fungi form a beneficial connection to the plant, in which they each trade nutrients. The seeds of parasitic plants, though, also possess the ability to sense strigolactones, which prompt them to germinate, attach to the host root and syphon off nutrients.

"It's kind of like root radar," said Nelson. "But the incredible thing is that this strigolactone detection system seems to have evolved from plant genes the normally control a seed's ability to detect fire."

Interestingly, the researchers also found that during the evolution of parasitic plants, the gene that detects smoke in plants and signals when certain plants should grow actually duplicated and some copies switched to become strigolactone detectors. This critical switch is what allows parasites to recognize and attack nearby hosts.

The findings reveal a bit more about parasitic plants and show what steps could be taken in order to create methods in order to deter them.

The findings are published in the journal Science.

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