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Hidden: Where are the Seeds in a Pinecone?

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Author: Janice VanCleave

Problem

Where are the seeds in a pinecone?

Materials

  • several sheets of newspaper
  • 2 old washcloths
  • 3 to 5 immature pinecones (small pinecones with tightly closed scales)
  • timer (optional)
  • adult helper

Procedure

  1. Spread out the newspaper on a table.
  2. Wrap a washcloth around each end of one of the pinecones.
  3. Holding a washcloth-covered end in each hand, twist the cone back and forth several times to loosen its scales. NOTE: If it is too difficult to twist the cone, soak all of the cones in water for 2 to 3 hours. Ask an adult for help if it is still too difficult to twist the cone.
  4. Hidden

  5. While holding the base of the cone with the cloth, use the fingers of your other hand to pull out several scales near the tip of the cone.
  6. Look for two seeds on the inside of each scale, as shown. NOTE: If you do not find seeds, repeat steps 2 to 4 with another pinecone.

Results

Two seeds, each attached to a paper-like wing, are found on the inside of the scales of the pinecone.

Why?

The pinecone contains the seeds of a pine tree. Pine trees are conifers, nonflowering plants that reproduce by forming cones. Most conifers are evergreen (having leaves that remain green all through the year) trees with small needle-shaped leaves and two types of cones. One is a small cone, called the pollen cone, which contains pollen and forms in groups at the tip of a branch. The other is a seed cone, which contains seeds and usually forms as a single cone away from the tip of a branch.

In the spring, wind blows pollen grains from the pollen cones to the seed cones. The pollen grains form sperm that fertilize the eggs at the base of the seed cone's scales. Each fertilized egg develops into a plant embryo, which is part of the seed. It can take two or more years for the seeds to develop completely. During the seed development stage, the cone grows larger, and the scales close tightly to protect the seeds.

Hidden

Hidden

Let's Explore

Are seeds found only inside the scales at the tip of the cone? Repeat the experiment, examining scales from tip to base. Science Fair Hint: Pull the scales out far enough to see the seeds, then photograph the cone. Use the photo as part of a project display.

Show Time!

  1. When the seeds have completely developed, the scales of pinecones open slightly and the seeds fall to the ground or are blown by the wind. Low humidity (wetness of the air) causes the cones to dry. Demonstrate the effect that drying has on the opening or closing of the cone scales. Have an adult heat cones to dry them. Line a cake pan with aluminum foil. Place 4 to 6 pinecones in the pan. Half of the cones should have open scales and half should have closed scales. Have an adult put the pan in an oven set to low and bake the cones for 30 minutes. After 30 minutes, have the adult remove the cones from the oven. When the cones have cooled, observe the position of the scales. NOTE: Save the pinecones for the next experiment.
  2. Determine the effect that rain and/or high humidity have on pinecone scales. Place one of the pinecones from the previous experiment in a glass of water. Observe the position of the cone's scales as often as possible for 30 to 45 minutes. Repeat, using the other pinecones. Take photographs of the cones before and after you soak them, and display the photos to represent the results.

Check it Out!

Conifers are gymnosperms, which are nonflowering plants with seeds. Their seeds are uncovered, meaning they are not found inside fruits but in cones. Use a biology text to find out more about the reproduction of gymnosperms. What are male and female gametophytes? What is a sporophyte? Use the information to prepare a display chart representing stages of the life cycle of a gymnosperm, such as a pine tree.

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