Wounded plants: How they coordinate their healing

Arabidopsis thaliana
Arabidopsis thaliana. Credit: Wikipedia.

When we cut our fingers, blood rushes out of the wound to close it. However, the vegetable we just wanted to slice and dice, would have reacted completely differently to this injury. Scientists at the Institute of Science and Technology Austria (IST Austria) investigated how plant cells heal wounds. In their results, published in PNAS on June 15, the researchers discovered that the hormone auxin and pressure changes are crucial to regeneration.

All suffer injuries. Animals and humans have movable cells, specialized in finding, approaching, and healing . Plant cells, however, are immobile and can't encapsulate the damage. Instead, adjacent cells multiply or grow to fill the injury. In this precision process, each unique cell decides whether it will stretch or divide to fill the wound. Even though scientists study regeneration in since the mid-19th century, the cell's 'reasons' for either choice remained unclear.

Now, scientists in the group of Professor Jiří Friml from the Institute of Science and Technology Austria (IST Austria) discovered that the hormone auxin and pressure guide the plant's way of regenerating.

"It is incredibly fascinating how robust and flexible plant regeneration is, considering how static those organisms are," says Lukas Hoermayer, a leading scientist in this study.

To investigate wound healing, the scientists injured a thale cress root with a laser. They then tracked cells during regeneration with a microscope. The scientists found that the hormone auxin, which is essential in and development, also plays a vital role in wound healing. It builds up in those cells directly touching the wound and facilitates the plant's response to injury.

The scientists used live microscopy to track the thale cress root while healing. When they interfered with the auxin amount, either no cells or too many cells responded to the wound, sometimes leading to tumorous swelling of the root. Credit: Lukas Hoermayer / IST Austria

When the scientists artificially changed the auxin amounts, either no cells or too many cells responded to the wound. This uncoordinated process, sometimes even led to tumorous swelling of the root.

"Only the precise coordination of many cells throughout the whole tissue yields a defined and localized wound response," explains Lukas Hoermayer.

To investigate wound healing, the scientists injured a thale cress root with a laser. They observed extreme pressure changes in the tissue at the moment of wounding. Credit: Lukas Hoermayer / IST Austria

Furthermore, the team recorded a pressure change within the plant, caused by the collapsing of the wound. When the scientists reduced the cellular pressure before cutting the plant, the pressure difference vanished, and the regeneration was weakened.

By observing plant regeneration and modifying it with chemical treatments, the scientists identified auxin concentration and as governing processes. Their results advance the understanding of how roots manage to heal wounds and hence survive in sandy soil or the presence of root-attacking herbivores.


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More information: Lukas Hoermayer el al., "Wounding-induced changes in cellular pressure and localized auxin signalling spatially coordinate restorative divisions in roots," PNAS (2020). www.pnas.org/cgi/doi/10.1073/pnas.2003346117
Citation: Wounded plants: How they coordinate their healing (2020, June 15) retrieved 4 July 2020 from https://phys.org/news/2020-06-wounded.html
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