How plant roots regenerate their tips to ensure growth

The growth of plants is a fascinating process that – despite all we know about it – scientists are still researching intensively to this day. One thing about plant growth that has puzzled scientists is the process of root cap replacement. The root cap protects the fragile tip of the root as a plant grows, and is replaced every few hours when the old cap is lost and a new one replaces it.

But scientists have wanted to know how the cells at the tip know when to die, and how cells further back know that it’s time to divide and form a new layer? These questions can now be (partially) answered, thanks to new research published in Nature Plants.

Researchers at the University of Oslo and the Institute of Science and Technology Austria (IST Austria) have observed for the first time regular cycles of root tip loss and regrowth in real time. In their work, they uncovered the signal and receptor that coordinate this process.

The researchers discovered the signal and receptor that facilitate communication at the root tip. Cells in the root cap secrete the signal peptide IDL1, which diffuses through the root tip. The peptide IDL attaches to the receptor protein HSL2 on the cells at the root apical meristem, which divide to form a new root cap. Through this, the outer root cap cells are shed and the inner cells that divide to replace them are able to communicate.

Root caps are lost at a rate of about one every 18 hours. “Because root cap loss and replacement is slow, you cannot observe it under a normal microscope set-up,” says Jiri Friml of IST Austria. To compensate for this, his group used a laser scanning microscope flipped on its side, which is a set-up they previously developed and led to them producing the winning video in last year’s “Nikon Small World in Motion Competition.”

With this microscope set-up, they could observe root growth over three days and see the periodicity of root cap peeling and cell death. “Our vertical microscope set-up and automatic tracking allowed us to observe how root caps are lost in natural conditions,” says Friml. “These tools enabled us to see how root cap loss actually happens and how the cells further back divide.”

This discovery not only shows the complexities of the inner working of plants, but it also shows that collaboration and the utilization of ingenuity within science can help us learn more about the world around us.

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By Connor Ertz, Earth.com Staff Writer