The fastest-growing plant in the world is known as duckweed or Wolffia. It grows on every continent except Antarctica, has no roots, grows in fresh water, and develops a single leaf-stem fusion structure about the size of a pinhead that's called a frond. Researchers are learning more about the rapid growth abilities of the plant by studying its genes, and the work has provided new insight into plant biology. The findings, which have been reported in Genome Biology, may help scientists engineer plants that can increase carbon storage, or trade certain functions like root growth for others like pest defense.
"A lot of advancement in science has been made thanks to organisms that are really simple, like yeast, bacteria, and worms," said the first study author Todd Michael, a research professor in Salk's Plant Molecular and Cellular Biology Laboratory. "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."
Wolffia's reproduction is more like a yeast than a plant; a daughter buds from a mother plant, and it can only take a day for the plant to double in size. These features are leading some researchers to investigate its potential as a source of food; people are already eating it in some parts of Southeast Asia.
In this study, the researchers subjected Wolffia to cycles of light and darkness and then assessed which of the plant's genes were active when. The findings were striking; Wolffia is not like most plants, which perform certain functions based on the time of day - like photosynthesis, which requires sunlight.
"Surprisingly, Wolffia only has half the number of genes that are regulated by light/dark cycles compared to other plants," Michael said. "We think this is why it grows so fast. It doesn't have the regulations that limit when it can grow."
The work also revealed that plant genes that have been linked to root growth and pest defense weren't in Wolffia's genome. "This plant has shed most of the genes that it doesn't need," Michael explained. "It seems to have evolved to focus only on uncontrolled, 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," added Howard Hughes Medical Institute Investigator, study co-author, and Professor Joseph Ecker, who is also director of Salk's Genomic Analysis Laboratory. "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 researchers want to learn more about engineering new plants that are optimized to behave in certain ways, and that research has many applications in agriculture, especially as the threat of climate change looms large.