Duckweed is the fastest growing plant in the world. Now we know why

Waterway caregivers have complained about this for decades, but no one seemed to know why duckweed, considered the fastest growing plant in the world, is spreading so rapidly in many lakes and ponds. Now, a group of researchers seem to have found the answer, claiming it is about the plant’s ability to grow rapidly in the dark.

Image credit: Flickr / Liu Tao.

The duckweed family includes 37 species and is found almost all over the world. Also known as Wolffia, the plants float on water, are easy to harvest, and can even grow on sewage. They range from less than a millimeter to just a few millimeters in size and lack roots that contain only the green things you see floating frond.

Some strains of the plant have very high protein levels, which is why researchers have described them as more nutritious than salad (yes, you can eat it). As its name implies, duckweed is eaten by ducks, as well as other animals, and even humans – but it acts much like a weed. It grows very quickly, especially in water-rich foods such as nitrogen and phosphate.

“A lot of progress in science has been made thanks to really simple organisms, such as yeast, bacteria and worms,” said Todd Michael, first author of the paper looking at duckweed, in a statement. “The idea here is that we can use an absolutely minimal plant like Wolffia to understand the fundamental workings of what makes a plant a plant.”

Working with a group of researchers from the Salk Institute in California, Michael focused on the characteristics in Wolffia’s genome that could explain its rapid growth. The team grew the plants in light / dark cycles to establish which genes were active at different times of the day. The results were surprising.

Most plants are light-sensitive, which means they grow especially in the morning in response to sunlight. At night they grow differently or more slowly. But this was not the case with Wolffia. The researchers found that the plant has half of the genes that are regulated by light / dark cycles compared to other plants – so it can grow more at night. “It doesn’t have the regulations that limit when it can grow,” Michael said.

But that’s not its only distinguishing feature. The researchers found that the genes usually linked with elements of behavior in plants such as defense mechanisms and root growth are not present in duckweed. For Michael, this means that the plant has shed the genes it doesn’t need, evolving to focus on unbridled and rapid growth.

“Data on Wolffia’s genome can provide important insights into the interaction between how plants develop their body plan and how they grow,” said Joseph Ecker, co-author of the journal. “This plant promises to become a new laboratory model for studying the central characteristics of plant behavior, including how genes contribute to different biological activities.”

The findings will help scientists understand how plants make trade-offs between growth and other functions, such as removing roots and defending themselves against pests, the researchers argued. The findings could help project new plants that are optimized for specific functions, such as increased carbon storage to help address climate change.

Previous studies have looked at duckweed but focused on something else instead of its rapid growth. Researchers in Israel have argued that mankai, a high-protein form of duckweed, could be the next superfood, as it controls blood sugar levels after people eat carbohydrates, according to their findings.

The study was published in the journal Genome Research.