Memory Built Into DNA

When a plant survives a drought, it lays down chemical marks on its DNA that prime faster, stronger responses to the next dry spell. Heat stress can also loosen or tighten chromatin — how the DNA is packaged — so stress-response genes become easier to switch on later.

Some of these molecular settings travel into the seeds, giving part of the next generation a head start. Just how durably the marks are passed on is still being worked out.