Abstract

Objective

In this experiment you will investigate the productivity of different fruits by counting the number of seeds produced.

Introduction

Many plants grow fruit to enclose and protect their seeds which need to spread out in order to grow more new plants. But animals love to eat sweet and juicy fruit, so why would a plant put seeds into something that will get eaten? At first this doesn't seem like a very good way for a plant to protect its seeds, why would this be beneficial?

Here you can see many different kinds of fruit, each cut open to reveal the seeds inside. (image from Dr. Renfroe, James Madison University)

Seeds are not actually digested along with the fleshy part of a fruit when it is eaten by an animal. Why can this be a good thing for plants? This is the gross part! The seeds are spread out by the animal after the fruit is digested and the animal poops. The seeds are then deposited, along with a little bit of fresh fertilizer, and can grow into a new plant. This is called seed dispersal, and is only one strategy that plants use to spread out seeds and make more plants.

Fruits and vegetables are good and good for you, which is a good thing for a plant. By making fruit that is sweet and tasty, plants can lure animals to eat the fruit and disperse their seeds. You might think that all fruit-bearing plants would pack as many seeds as possible into each fruit to maximize the number of new seeds that will grow. But in fact, different plants each have different strategies for seed production. Some fruits produce many many seeds, to make sure that some of them will grow even if others fail. Other fruits put all of their resources into producing and protecting one very large seed.

How do some of your favorite fruits produce seeds? What strategies do they use? In this experiment you can measure the productivity of some of your favorite fruit by counting the number of seeds they produce. Which types of fruit will make the most seeds? Are some fruits more productive than others?

Terms, Concepts, and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• fruit
• seed
• dispersal
• productivity

Bibliography

• Renfroe, M.H. and Morgen, Stacey. 1997. "Seeds and Fruit." James Morgan University. [2/15/06]
  http://www.jmu.edu/biology/k12/fruitdev/seed.htm
• Visit the website of "The Great Plant Escape" to help Detective Le Plant solve 6 cases, learn about plants, use the glossary to learn new terms and see pictures of plant parts:
  Stack, Greg, et. al. 2005. "The Great Plant Escape." University of Illinois, Urbana-Champaign. [12/13/05]
  http://www.urbanext.uiuc.edu/gpe/index.html
• Glover, David. 2001. How do Things Grow? Hands-on Experiments That Make Science Fun.. New York, NY: Dorling Kindersly Inc.
• Gibbons, Gail. 1991. From Seed to Plant.. New York, NY: Holiday House.

Materials and Equipment

• many different types of fruit
• knife to cut the fruit (get your parents help!)
• small paper cups
• permanent marker

Experimental Procedure

1. Go to the grocery store and pick out different kinds of fruit. Don't just stick to the traditional fruits, try some unique fruits as well. Some types of fruit you might think are vegetables! Also remember to try peppers, tomatoes, cucumbers and squash.
2. Make a list of all of the fruits you have chosen in a data table. Also include a place to write the number of seeds, number of fruits counted and the productivity of each type of fruit.

   Type of Fruit	Number of Fruits Counted	Total Number of Seeds	Productivity (number of seeds/fruit)
   Apple
   Grape
   Bell Pepper
   etc...

3. Write the name of each type of fruit on a paper cup. You will use the cup to hold the seeds from that fruit. Remember that each cup is only for one type of seed!
4. Begin to dissect your first fruit, removing the seeds and putting them in a paper cup. Do one type of fruit at a time so that the seeds do not mix together. For each type of fruit you should dissect a few fruits and add your seeds together to get a better set of data. Write down the number of fruits that you used to collect seeds in your data table.
5. When you are done removing the seeds, count the number of seeds in the cup and write the number in your data table.
6. Repeat steps 3–5 for each type of fruit. Some fruits might be tricky, so here are some tips:
   • Strawberry seeds are on the outside of the fruit, so pick them off using your fingernail or a toothpick.
   • Bananas do have seeds, but they are very tiny. Look for the tiny black spots on the inside of a banana slice. you can try to count them, but it is not recommended.
   • Pepper seeds are spicy! Do not touch your eyes after handling the seeds. Use a mild pepper variety, like a Bell pepper if you are very sensitive.
   • Avoid trying seedless varieties of grapes, oranges, cucumbers and melons.
   • Remember that a "pit" is the same as a seed, and will be found in "stone fruits" like cherries, peaches, nectarines, plums and apricots.

7. After you have counted the number of seeds inside each type of fruit, you are ready to calculate the productivity for each type of fruit. The productivity of each fruit is measured by the number of seeds per piece of fruit. To do this calculation, divide the total number of seeds by the number of pieces of fruit that you counted for each variety. For example, if you counted 20 seeds total in 5 grapes, then the productivity of a single grape would be 4 seeds per fruit. Write your answers in the data table.
8. Make a graph to show the number of seeds per fruit. A bar graph works best for this type of experiment. Put the number of seeds on the left side of the graph (Y-axis) and draw each bar up to the correct number. Remember to label each bar of your graph with the correct type of fruit.
9. Which fruits had the most seeds? Which fruits had the least seeds? Were there any patterns of seed production that you noticed? Did similar types of fruits produce similar numbers of seeds?

Variations

• Is fruit size related to seed production? You can use a ruler to measure the fruits before you count the seeds to see if larger fruits tend to produce more seeds than smaller fruits. You can also use a scale to weigh each fruit as a different way to measure fruit size.
• Do fruits that take a longer time to grow make more seeds than slower growing fruits? You can find information on the growth of some fruits by looking at seed packets for tomatoes, peppers, squashes and melons. Each packet will tell you how long the fruit will take to germinate (sprout it's seeds) and mature (grow into a plant that will produce fruit for harvest).
• Are seedless fruit varieties really seedless? Buy several different varieties of seedles fruits. Dissect the fruits and look for seeds. Are these varieties completley seedless, or simply have fewer seeds than normal? Can you calculate the decreased productivity of seedless varieties compared to normal varieties by counting the number of seeds per fruit?
• What about other dispersal methods, like wind or water. Can the appearance of the seed give you clues as to how it is dispersed? Look at the morphology of different seeds for evidence of dispersal method, like tufts on dandelion seeds for wind dispersal or hooks on stickers for catching in animal fur.

• For more science project ideas in this area of science, see Plant Biology Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Last edit date: 2008-04-09 12:00:00