Grades 6–8 · Organisms
Why can some buried seeds begin growing after a fire?
Some plants leave seeds in soil that stay alive without immediately germinating. This dormant seed bank can persist until a suitable environmental signal arrives. For certain species, changes associated with fire supply that signal.
In the diagramSome seed coats become more permeableDormant exampleAfter a suitable heat cuelimited water entrywater reaches the embryo
In some hard-coated seeds, heat changes the outer covering so water can enter more readily. In other species, compounds from smoke or burned plant material affect germination signals. These are different mechanisms with a similar possible outcome.
After a fire, reduced plant cover may provide more light and space. A seed that germinates then may encounter less competition. It still needs enough water, suitable temperatures and a surviving embryo to establish a seedling.
This adaptation is specific to particular plants and fire conditions. A very intense fire can kill seeds, and repeated fires can arrive before new seeds are produced. The mechanism is a timed response to environmental change, not a general rule that burning always helps plants.
About this explanation
Starting knowledge: Know that a viable seed can remain dormant and that germination requires suitable environmental conditions.
Sources
- National Park Service — Point Reyes Fire and Fuels: Fire-triggered Germination