Waterway caretakers have complained about it for decades, but no one seemed to know why duckweed, considered the world’s fastest-growing plant, spreads so rapidly in many lakes and ponds. Now, a group of researchers seems to have found the answer, claiming it’s all about the plant’s capability to grow quickly in the dark.
The duckweed family includes 37 species and can be found pretty much all over the world. Also known as Wolffia, the plants float on water, are easy to harvest, and can even grow on wastewater. They range from less than a millimeter to only a few millimeters in size and lack roots, containing only the green stuff 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 a 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 very much like a weed. It grows very fast, especially in water-rich with nutrients such as nitrogen and phosphate.
“A lot of advancement in science has been made thanks to organisms that are really simple, like yeast, bacteria and worms,” Todd Michael, first author of the paper looking at duckweed, said 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 fast growth. The team grew the plants under 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 sunshine. At night, they grow differently or slower. But this wasn’t the case of Wolffia. The researchers found the plant has half the number of 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,” said Michael.
But that’s not its only distinctive feature. The researchers found that the genes usually linked with elements of behavior in plants such as defense mechanisms and root growth aren’t present in duckweed. For Michael, this means the plant has shed the genes it doesn’t need, evolving to focus on uncontrolled and fast growth.
“Data about the Wolffia genome can provide important insight into the interplay between how plants develop their body plan and how they grow,” Joseph Ecker, a coauthor of the paper, said in a statement. “This plant holds promise for becoming a new lab model for studying the central characteristics of plant behavior, including how genes contribute to different biological activities.”
The findings will help scientists to understand how plants make trade-offs between growth and other functions, such as putting down roots and defending themselves from pests, the researchers argued. The findings could help to design 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 different rather than its fast growth. Researchers from Israel argued that mankai, a high-protein form of duckweed, could be the next superfood because it controls blood sugar levels after people eat carbohydrates, according to their findings.