Plant & zo
The science of plants and more
Plants have different strategies to spread their seeds. There are those that use animals, with the seeds traveling in the fur or stomach of the animal. Then there are those that trust the wind to disperse their seeds. A third group of plants spreads them all by themselves. They shoot their seeds as far away as possible. Like the plants of the sorrel family. Which shoot their seeds like a machine gun into the wide world. How they do that? Chinese researchers found out.
First, they analysed how the plant shoot a single seed. Zooming in, the researchers noticed that each seed has its own snug chamber with a single opening. The seed itself is surrounded by a coat. This coat is made up out of two cell types. The cells on the inside can take up easily, and will swell, expanding. While the cells on the outside can’t take up any water or swell. The swelling inside coat cells will put pressure on the outside cells. Priming them.
The nicest thing of it all, is that it hardly cost any energy at all
Then a small tremble, from the wind for example, will be enough to break the outside layer of the coat. This enables the inside coat cells to stretch out completely. Super-fast peeling off the coat, like a banana skin. The coat is pressing against its chamber walls, thereby pressing the seed out, shooting the seed away.
Next, the researchers analysed how the plant managed to shoot one seed after another. This had to do with the way the seeds had arranged themselves, touching top and bottom. This, noticed the researchers, was the key to machine gun like shooting seeds. Every shooting seed gives a small bump against its neighbour. This breaks the outside layer of that neighbour’s coat, shooting it out of its snug chamber, and on its way bumping into its other neighbour. Resulting in a rain of shooting seeds.
The nicest thing of it all, is that it hardly cost any energy at all. Just taking up water is enough to prime the seeds. Then, a small tremble from outside is all it takes to spread the seeds as far as possible.
Li, S., Zhang, Y. and Liu, J. (2020) Seed ejection mechanism in an Oxalis species. Scientific Reports 10,8855 https://doi.org/10.1038/s41598-020-65885-2