(
Pine trees have weird leaves (their needles), and their cones are actually a weird way for them to hold and disperse their seeds. Other plants use seed pods (like peas) or fruits (like…okay, I’m not going to insult your intelligence; you know what fruit is) but pine trees use their cones. You may notice, walking by pine trees in different weather, that sometimes the cones are closed, and sometimes they are open. Today’s experiment will be to figure out why that is, and what sorts of things affect how pine cones open and close.
Materials
- 3-5 pine cones
- A big bowl
- Water
- An oven
- A cookie sheet
- Oven mitts
- An adult
Process
- Gather up your pine cones. You can do this on a hike in the woods or, if you’re more of an indoorsy type, you can buy some at a craft store.
- Observe your pine cones. Are they closed and squeezed tight, or are they open?
- Either way, the first part of our experiment is to put the pine cones into a big bowl full of water.
- Observe your pine cones every few minutes for half an hour to an hour. What happens to open pine cones? What happens to closed pine cones?
- After a long soak, all of your cones should be closed. But how can we make them open again?
- For part two, get your adult to help you. Preheat the oven to 200 degrees. Put your pine cones on your cookie sheet and put them in the oven for half an hour. What happens to them when they come out?
- What do you think is going on here? What are the differences between the water and the oven? How can you make them open and close at your whim?
Summary
Since pine cones are seed holders, the way they open and close has to do with either holding onto or releasing seeds into the environment to sprout. When you put your cones into the water, they closed, and they did it pretty quickly. But then when you put them in the oven for a while, they opened back up again. The big differences are that the water is cold and wet and the oven is warm and dry.
When pine cone scales (that’s what each piece is called) are open, it allows seeds to be pollinated and fly away from the tree to hit the ground elsewhere and hopefully sprout. When they are closed, that can’t happen. Pine cones hold onto their seeds in cold, wet weather because in that environment, seeds are more likely to fall right down next to the tree and sprout there, where they can’t get a lot of sunlight or nutrients because the parent tree is already using them. In warm, dry weather, though, the seeds are more likely to get caught in the wind and fly far away to a place where they might have more access to sunlight and soil nutrients. So pine cones opening and closing is kind of a way for the tree to make sure its children have a good, long life.
