This pattern, which the researchers dubbed “orixate” phyllotaxis, is not just a onetime anomaly, as plants from other taxa (like the “red-hot poker” flower Kniphofia uvaria, or the crepe myrtle Lagerstroemia indica) alternate their leaves in the same complicated sequence. Qwert1234 via Wikicommons under CC BY-SA 4.0 japonica shrub, which is native to Japan and other parts of East Asia, grows leaves in an alternating series of four repeating angles: 180 degrees, 90 degrees, 180 degrees again, then 270 degrees.Īn Orixa japonica shrub with the various divergence angles of the leaves visible. While most leaf arrangement patterns keep a constant divergence angle, the O. More than 10 years ago, an idea came to me that some changes in the inhibitory power of each leaf primordium may explain this peculiar pattern.”īotanists use the divergence angles, or angles between consecutive leaves, to define a plant’s phyllotaxis. “But in this special plant, Orixa japonica, the phyllotactic pattern is not symmetric, which is very interesting. “In most plants, phyllotactic patterns have symmetry-spiral symmetry or radial symmetry,” says University of Tokyo plant physiologist Munetaka Sugiyama, senior author of the new study. Their updated model, described in a new study in PLOS Computational Biology, not only reproduces the once-elusive pattern, but it also may describe other, more common arrangements better than previous equations, authors say. A team led by University of Tokyo researchers studying a shrub known as Orixa japonica found that earlier equations couldn’t recreate the plant’s unusual structure, so they decided to rethink the model itself. However, certain leaf arrangements continue to stump popular models for plant growth, including the Douady and Couder equations (known as DC1 and DC2) that have dominated since the 1990s. Common alternate types are distichous phyllotaxis (bamboo) and Fibonacci spiral phyllotaxis (the succulent spiral aloe), and common whorled types are decussate phyllotaxis (basil or mint) and tricussate phyllotaxis ( Nerium oleander, sometimes known as dogbane). Leaf arrangement with one leaf per node is called alternate phyllotaxis, whereas arrangement with two or more leaves per node is called whorled phyllotaxis. ![]() The current consensus is that the movements of the growth hormone auxin and the proteins that transport it throughout a plant are responsible for such patterns. The ever-fascinating Fibonacci sequence, for example, shows up in everything from sunflower seed arrangements to nautilus shells to pine cones. Based on the idea that already existing leaves have an inhibitory influence on new ones, giving off a signal to prevent others from growing nearby, scientists have created models that can successfully recreate many of nature’s common designs. One assumption that has been central to the study of phyllotaxis, or leaf patterns, is that leaves protect their personal space. In fact, these patterns are consistent enough that cold, hard math can predict organic growth fairly well. Take a closer look, though, and you’ll find that a few curiously regular patterns pop up all over the natural world, from the balanced symmetry of bamboo shoots to the mesmerizing spirals of succulents. ![]() ![]() To the untrained eye, plants may appear to grow rather impulsively, popping out leaves at random to create one big green jumble.
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