Heavy locks, imposing gates and motion-sensing lights can help to fortify your home and safeguard your belongings against thieves. On the other hand, they can also advertise the fact that you have stuff worth stealing. Extra security can be a double-edged sword.

This is as true for plants defending their tissues as it is for humans defending their homes. Maize plants, like many others, protect themselves with poisons. They pump their roots with highly toxic insecticides called BXDs, which deters hungry mandibles. But these toxins don’t come free. The plant needs energy to act as its own pharmacist, so it distributes the poison to the areas that deserve the greatest fortification – its crown roots.

Maize seedlings grow roots either from the