Fastest-growing plant spreads so quickly because it grows in the dark, study finds
For decades, the speed at which duckweed carpets rivers, ponds and canals has puzzled and irritated the caretakers of Britain's waterways.
The plant is such a pest because it forms a thick growth on the surface of water, choking out other life.
Now, scientists have found out that the world's fastest-growing plant spreads so rapidly because unlike other vegetation, it grows quickly in the dark.
Most plants are light sensitive, meaning they grow in response to sunshine, and often grow differently or more slowly at night.
However, new research from the Salk Institute in San Diego, published in Genome Research, has found that duckweed does not have the gene for photosensitivity switched on in the way other plants do.
Professor Todd Michael, first author of the paper, explained: "Surprisingly, Wolffia only has half the number of genes that are regulated by light/dark cycles compared to other plants,
"We think this is why it grows so fast. It doesn't have the regulations that limit when it can grow."
The ground-breaking genome sequencing project found how plants make trade-offs between growth and other functions, such as putting down roots and defending themselves from pests. This research has implications for designing entirely new plants that are optimised for specific functions, such as increased carbon storage to help address climate change.
The researchers grew duckweed under different light-dark cycles and analysed which genes were switched on. The researchers also found that genes associated with other important elements of behavior in plants, such as defense mechanisms and root growth, are not present.
"This plant has shed most of the genes that it doesn't need," Prof Michael added. "It seems to have evolved to focus only on uncontrolled, fast growth."
Because duckweed grows so quickly, scientists think they could use that feature to grow food for a rapidly increasing global population. The plant itself is already eaten in parts of Southeast Asia, where it's known as khai-nam, which translates as "water eggs."
