Miniaturisation – an extreme reduction in size – is an extraordinary phenomenon found throughout the natural world. Although it usually comes with a cost, such as loss of organs. But duckweeds, the smallest flowering plants on the planet, have found a way to get around paying that cost, according to a new study published in the journal Current Biology.
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Miniaturisation is present both in the plant and animal kingdoms, but it’s much better studied and understood in animals. Miniature frogs, for example, experience a reduction of lungs, while tardigrades (an eight-legged segmented micro-animal) lost body segments at some point in their evolution – and so on.
Duckweeds belong to the family Araceae – and while they can measure just a few millimetres across, their relatives include some of the largest herbaceous plants. For example, the giant elephant ear (Alocasia macrorrhizos) can produce leaves up to 2m wide. Meanwhile, Wolffia globosa, a species of duckweed, can be as tiny as 0.1-0.2mm in diameter.
Researchers at University of Nottingham wanted to find out how a complete body plan can be packed into such a tiny space. As it turns out, duckweeds are masters of compression.
Through gene expression analysis and cutting-edge microscopy, the scientists were able to determine that duckweeds retain the same basic building blocks found in the shoots of larger plants – but these structures have been dramatically compressed and fused together.
“While miniaturisation in animals is often associated with the loss of organs or body structures, we have revealed that duckweeds have taken a different route,” said Dr Anthony Bishopp, lead author of the study.
“What surprised us is that, when we looked closely, the basic organisation of the shoot was still there. Rather than throwing away parts of the blueprint, duckweed appears to have compressed and fused its components into an incredibly compact plant. That gives us a new way of thinking about how plants can evolve to become so small.”
Wider use
The finite limits and shrinking availability of agricultural land represent one of the most critical challenges to global food security and environmental stability. As such, research into these tiny plants is advancing rapidly, driven by growing interest in them as a potential source of food (and possible crop for future space missions). Duckweeds are high in protein (30-45 per cent of their dry matter) – according to The Charm of Duckweed website, the plant can produce 3-7 tonnes of proteins per hectare in the EU.
Unlike most of the crops we grow today, which have been shaped by thousands of years of domestication and selective breeding, the potential of duckweed remains largely unexplored.
“Duckweeds are astonishingly small, so it is tempting to think of them as either primitive plants or simply as having lost parts, but this is not the case. Our research adds to growing evidence from across the research community about this plant and will help efforts to turn them into a future crop,” said Dr Alex Ware, co-author of the study.
Read the full findings here.
Top image: Duckweed on a pencil. Credit: University of Nottingham
