Flashes of light show how plants signal distress

Simon Gilroy and his lab discovered how glutamate triggers calcium waves in plants, warning them of danger. They developed special plants that fluoresce in the presence of calcium to observe this process. By inflicting various types of damage, they tracked calcium's spread and identified glutamate as the trigger.

Describe the methods used by the team to test the plants' responses to distress.

What did the scientists identify as the trigger for the waves of calcium?