They discovered how the world's smallest plants reduced their size without losing structures

Gene expression analysis showed that the frond combines leaf tissue at its ends with stem tissue in its central zone. (Illustrative image Infobae)Miniaturization is a phenomenon that runs through the kingdoms of nature: there are tiny frogs that lose part of their lungs, and tardigrades—microscopic eight-legged animals—that gave up body segments over the course of evolution. In the plant world, however, the process had barely been studied with modern tools. The question had persisted for decades: when a plant becomes extraordinarily small, does it lose organs the way animals do, or does it find another path? Duckweeds offer an extreme case. They belong to the family Araceae, the same one that groups together some of the largest herbaceous plants on the planet, such as the giant elephant ear, whose leaves can reach two meters wide. At the other extreme, the species Wolffia globosa measures barely between 0.1 and 0.2 millimeters in diameter. It is the smallest flowering plant in the world, a green disc that floats on the surface of the water and whose internal architecture was, until now, an enigma. A team from the University of Nottingham managed to decipher how these plants pack a complete body into such a reduced space, a finding that, in addition to transforming the understanding of plant biology, opens concrete paths for the food of the future, including long-range space missions. According to a study published in the journal Current Biology, the researchers carried out gene expression analyses—that is, measuring which genes are active in each tissue—along with state-of-the-art microscopy. The results revealed that duckweeds retain the same components found in the shoots of larger plants, but compressed and fused so drastically that they become almost unrecognizable from the outside. The species Wolffia globosa measures between 0.1 and 0.2 millimeters in diameter and is the smallest flowering plant on the planet. (Illustrative image Infobae) The body of a duckweed is called a frond, a flat green structure that for a long time generated debate among botanists: is it a leaf, a flattened stem, or a combination of both? To solve the mystery, the team compared two species of duckweed with water lettuce and taro, close relatives whose stems and leaves are easier to distinguish. The scientists separated the different parts of each plant and analyzed which genes were active in each one. The broad zones of the frond showed patterns similar to those of leaves, while a small central region resembled stem tissue. The tiny green disc seemed, then, to house more than one type of plant structure. Since gene activity alone was not enough to settle the question (different parts of a plant can use similar genes because they perform similar functions), the team turned to three-dimensional microscopy. Within the species Lemna minor they found a previously undescribed network, located near the center of the frond. That mesh contained material that strengthens cell walls and extended from the root zone toward the developing young plants. The researchers propose that this network marks the boundary of a very short stem, surrounded and wrapped by leaf tissue. "What surprised us is that, when we looked closely, the basic organization was still there. Instead of discarding parts of the blueprint, the duckweed appears to have compressed and fused its components into an incredibly compact plant," said Anthony Bishopp, lead researcher of the work and a member of the School of Biosciences at the University of Nottingham, according to the press release. The scientists identified through three-dimensional microscopy an internal network that delimits a very short stem wrapped by leaf tissue in Lemna minor. (Illustrative image Infobae) To understand how these plants remain so small, the team examined 131 individual fronds of Lemna minor at different stages of development. With a chemical marker capable of identifying cells preparing to divide, they verified that, in the early stages, division activity was distributed across much of the young frond. Over time, that activity became concentrated near the base, a pattern that matches the known development of leaves in conventional plants and that reinforced the identification of much of the frond as leaf tissue. In the final stage, the main body of the frond showed practically no cell division. The fronds then reached between two and four millimeters. This limited period of cell multiplication could be one of the mechanisms that keep the plant's size reduced, although the study clarifies that this is a possible explanation, not a proven cause: the team did not evaluate whether extending that period would produce larger specimens. Even when the mature frond stops generating new cells in its main body, the offspring continue their development around the mother plant. The researchers observed up to five young specimens clustered in the central zone, housed in protected cavities: some were just beginning to form, while others were already quite advanced. Their arrangement recalls that of the shoots waiting to grow from the stem of a larger plant, which reinforces the idea that, despite their unusual appearance, duckweeds retain a familiar mode of growth. The researchers are evaluating the potential of duckweeds as a protein source for human consumption and for space missions. (Illustrative image Infobae) The finding is not limited to the realm of evolutionary biology. Research on duckweeds is advancing rapidly because they spark growing interest as a source of food and protein. According to the University of Nottingham press release, they are also being studied as a possible crop for future space missions. Unlike most current crops, shaped by thousands of years of domestication and selective breeding, the potential of these plants remains largely unexplored. Understanding the organization of their body provides an essential framework for knowing how they grow, develop, and function, and, ultimately, how their yield could be improved. "Duckweeds are astonishingly small, so it is tempting to think of them as primitive plants or ones that simply lost parts, but that is not the case. Our research adds to the growing body of evidence from the scientific community about this plant and will contribute to efforts to turn it into a crop of the future," said Alex Ware, co-author of the study and researcher at the University of Nottingham, according to the press release. The work focused on the species with roots. Their smaller relatives, such as those of the genus Wolffia, also lack roots and the tissues that transport water and nutrients, which indicates that they underwent additional changes that this research did not address directly.