What’s the first image that pops into your head when you hear the word parasite? Most of us probably picture a worm-like organism latching onto a surface, or maybe even a tiny bug jumping from one animal to the next. What most people don’t think of as parasites though, are plants.
The unwelcomed garden guests
Like all types of parasites out there, parasitic plants obtain their required nutrients from a host, which in this case are other neighbouring plants. They have an organ called the haustorium that connects them to the tissues of a host and allows them to extract water and nutrients. This becomes a burden to farmland owners as crops are destroyed by the plants leeching off of them. To help prevent this, scientists have been trying to figure out how these parasitic plants are able to detect a host in the first place.
Finding the root of the problem
As the root of a plant develops, they release hormones called strigolactones that help form a beneficial nutrient-trading relationship with fungi. According to a recent study, however, the seeds of parasitic plants can also detect the presence of strigolactones in the soil, and this acts as their signal to begin germinating and attaching to the host for nutrients. These seeds have more patience than most humans possess, as they can remain dormant in the soil for years until they detect another plant nearby.
So where did this hormone-detecting ability come from? It turns out that it evolved from genes that normally allow seeds to detect forest fires. Many plants are able to recognize compounds from smoke and ash that have leeched into the soil after these fires, and this signals to them that their competition, such as large shady trees and dense forest cover, are likely gone from the area. With less competition for resources, this fire-detecting ability helps seeds determine the optimal time to grow successfully on their own.
Researchers have found that the fire-detecting genes likely duplicated over time, and some of these copies evolved to become strigolactone detectors instead. With this switch, parasitic plants developed the ability to identify and feed off of nearby hosts.
A battle against parasitic plants
While parasite infestations invade farmlands and reduce crop yields every year, developing countries are especially affected by this drawback as they have a heavier dependency on crops. But with the latest breakthroughs in understanding the mechanisms behind parasitic plants, researchers can now develop different ways to combat against them.
So far, one solution includes developing synthetic compounds that would interfere with a parasitic plant's ability to detect strigolactones, and therefore stop it from identifying and attacking nearby hosts. Another solution involves mimicking the strigolactone signal with modified chemicals. By spraying these chemicals over a field before every growing season, parasitic plants would be tricked into growing without the presence of any hosts around, and this would allow farmers to get rid of them without having to lose any crops.
Overall, parasitic plants aren't any less deadly than the typical parasites that first come to mind. With their clever detectors and long lasting patience, these plants may be waiting to strike in our very own backyards.