December 15, 2016
6 min read
Unlocking the Secrets of the Pinecone
By Science Buddies & Megan Arnett
Key concepts
Biology
Plant science
Temperature
Data
Introduction
Depending on where you live, this time of year the ground might be covered in snow, ice and, most importantly, pinecones! We see pinecones everywhere during the winter—in wreaths, on trees and in our yards. But did you know that pinecones have a vital job? They keep pine tree seeds safe, and protect them from the freezing temperatures during the winter! To protect their seeds, pinecones can close their “scales” tightly, keeping out cold temperatures, winds, ice and even animals that might eat their precious cargo.
In this activity we will observe how pinecones respond to different temperatures by mimicking changes in weather, all from our own kitchens! As an added bonus, after this activity your pinecones will be ready to be added to your house as a holiday decoration or as a reminder of the plants of the season.
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Background
Did you know that pinecones can stay on pine trees for more than 10 years before falling to the ground? During that time seeds for new pine trees grow under the scales of the pinecones. The scales protect the seeds from bad weather—and hungry animals. Eventually, however, the seeds need to be released so that they can grow into new trees. To make sure they have the best chance of finding fertile soil and growing into trees, the pinecone scales stay tightly closed when the weather is inhospitable to new seed growth—that is, when it’s very cold and damp outside. In contrast, when the weather is hot and dry, the seeds will have an easier time finding good soil for growing into trees. In these conditions the pinecone scales will open, allowing seeds to escape and drift away to find new ground to grow into new trees!
As you will observe in this activity, after pinecones fall from the tree they can still open and close; we will test the conditions that cause this—all from home!
Materials
At least three pinecones collected from outside
An oven
A large clear glass jar or bowl, large enough to hold about a cup of water
A measuring tape
Cold water
A timer
Tin foil
A piece of paper
Pencil or pen
A baking tray
A spoon or fork
Permanent marker
An adult helper
Ice (optional)
Preparation
With the help of an adult, preheat the oven to 250 degrees Fahrenheit.
Cover your baking tray with tinfoil.
Fill up the glass jar with cold water (including a few pieces of ice if available).
Use your permanent marker to label your pinecones. On the first one write the letter “A.” On the second pinecone write “B” and on the third write “C.”
On your paper, make three rows. Label the rows A, B and C. Draw six columns. Label the columns “Initial Length,” “Initial Circumference,” “Cold Water Length,” “Cold Water Circumference,” “Final Length” and “Final Circumference.”
Procedure
Use your measuring tape to measure the length of each each pinecone. For each pinecone, write down the length in the column Initial Length. For all measurements in this activity, use centimeters (cm).
Use your measuring tape to measure the circumference of each pinecone at its widest point. For each pinecone, write down the circumference in the column Initial Circumference.
Place pinecone A on the foil-covered baking tray. With the help of an adult, put the tray in the 250-degree F oven.
With the help of an adult, check the pinecone every 10 minutes to make sure it doesn't burn. Are the pinecones changing in any way as they get warmer? What do you notice about them as they get hot?
While pinecone A heats up, place pinecone B in the cold water. Use your spoon to hold it underwater. Keep it there for two minutes. What do you notice about the pinecone in the water? Does it sink or float? Why do you think this is true? Do you notice any changes as the pinecone sits under the cold water?
Remove the pinecone from the cold water.
Use your measuring tape to measure the length of pinecone B. Write down the length in the column Cold Water Length.
Use your measuring tape to again measure the circumference of pinecone B at the widest point. Write down its circumference in the column Cold Water Circumference. Compare the length and circumference of pinecone B in each column. Did its length or circumference change after you put it in cold water? If so, what kind of changes did you notice? Did it get larger or smaller? Do you notice any other changes about the pinecone? Does it look different? In what way?
After pinecone A has been in the oven for 45 minutes, with the help of an adult, remove it from the oven. Allow it to cool until you can handle it comfortably.
Use your measuring tape to measure the length of pinecones A, B and C. Write down their lengths in the column Final Length.
Use your measuring tape to measure the circumference of pinecones A, B and C at their widest points. For each pinecone, write down their circumferences in the column Final Circumference.
Compare the length and circumference of the pinecones for each column. If you like, you can use math to measure the changes using a few simple equations (and use the same equations to look for changes in length, by substituting length for circumference):
Initial Circumference of Pinecone A
Hot Circumference of Pinecone A
Change caused by heat on Pinecone A
Final Circumference of Pinecone A
Initial Circumference of Pinecone B
Cold Circumference of Pinecone B
Change caused by cold on Pinecone B
Final Circumference of Pinecone B
Initial Circumference of Pinecone C
Change caused by control conditions (air) on Pinecone C
Final Circumference of Pinecone C
Using the data collected, determine which pinecone had the biggest change from the initial length and circumference. Notice which pinecone had the smallest change. Why do you think some pinecones changed more or less than others? Do you notice any other changes in the pinecones? Do they look different? In what way?
Extra: After pinecone A is out of the oven, try putting it into the cold water. Remove it after several minutes and measure its length and circumference again. How does cold water affect the size and shape of the pinecones?
Extra: Try the reverse. Take pinecone B from the cold water and place it into the oven to heat up. What kind of impact does the heat have on the chilled pinecone? Is it similar to or different from the pinecone A, which was never in cold water?
Extra: Try lowering the temperature of the oven to 150 degrees F and testing the effect on the size and shape of another pinecone. Does it get larger than the one in the 250-degree F oven—or smaller? Why do you think this happens?
Extra: After taking the pinecones out of the oven and measuring, put them in the freezer overnight. When you take them out in the morning, measure their lengths and circumferences again, and compare them with the final measurements. Did the pinecones get larger or smaller? What other changes do you observe?
Observations and results
In this activity you observed and recorded the effect of different temperature and conditions on the size and appearance of pinecones. You might have noticed that placing pinecone B in the cold water caused its circumference to decrease. In response to cold and damp conditions, pinecone scales close tightly, making a natural shell to protect the seeds inside.
After taking pinecone A out of the oven you measured all of the pinecones to get their final measurements. When you compared the initial measurement of pinecone A, you should have observed that its circumference increased after being in the hot oven. The increase in the circumferences of the pinecones results from the scales of the pinecones opening up in response to the warmth of the oven. The pinecones think it's a warm summer day, and are ready to release their seeds!
More to exploreHow Plants Survive the Cold (or Not), from How Plants Work
Pinecone Opening in Warm Air, Time-Lapse Video, from Youtube
Pinecone Closing in Water, Time-Lapse Video, from Youtube
Science Activity for All Ages!, from Science Buddies
This activity brought to you in partnership with Science Buddies
