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How Many Seeds Do Different Types of Fruit Produce?

Difficulty
Time Required Very Short (≤ 1 day)
Prerequisites None
Material Availability Readily available
Cost Very Low (under $20)
Safety Adult supervision required when cutting fruit

Abstract

Do you like your strawberry jelly with or without the seeds? Are you glad to have a seed-free watermelon, or do you enjoy spitting the seeds into the garden? You might not like to find seeds in your fruit, but fruit is the plant's way of dispersing seeds to make new plants. How many seeds can be dispersed for each type of fruit? As they say, in one end and out the other!

Objective

Investigate the productivity of different fruits by counting the number of seeds produced.

Credits

Sara Agee, Ph.D., and Teisha Rowland, Ph.D., Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "How Many Seeds Do Different Types of Fruit Produce?" Science Buddies. Science Buddies, 5 Aug. 2014. Web. 27 Nov. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p019.shtml?from=Blog>

APA Style

Science Buddies Staff. (2014, August 5). How Many Seeds Do Different Types of Fruit Produce?. Retrieved November 27, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_p019.shtml?from=Blog

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Last edit date: 2014-08-05

Introduction

Many plants grow fruit to enclose and protect their seeds, which need to spread out in order to grow more new plants. You can see many different kinds of fruit in Figure 1 below. 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 does not seem like a very good way for a plant to protect its seeds, so why would making tasty fruit be beneficial?

Photographs of fruit whole, cut open, and isolated seeds.
Figure 1. Here you can see many different kinds of fruit, which have been cut open to reveal the seeds inside. Some seeds that have been removed from the fruit are shown on the far right.

When an animal eats fruit, the fleshy part is digested but the seeds are not. Why can this be a good thing for plants? This is the gross part! The seeds pass without harm through the digestive system and are spread out by the animal when the animal poops. The seeds are then deposited farther from the parent plant, along with a little bit of fresh fertilizer, and can grow into a new plant. Spreading out seeds to make new plants grow in areas away from the parent plant is called seed dispersal. Spreading seeds by using animals is only one seed dispersal strategy that plants use. By making fruit that is sweet and tasty, plants can lure animals to eat the fruit and disperse their seeds. Can you think of some other seed dispersal strategies that plants use?

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.

Fruits are divided into three general groups, and each group is defined by how the flower turns into the fruit. The "simple fruits" group makes up most of the fruits we encounter. Cucumbers, melons, and squash are all one type of simple fruit (specifically a type called pepo, which are berries). These fruits all have a hard rind and are softer and watery inside. Do you think they all make a similar number of seeds? Tomatoes, grapes, kiwifruit, oranges, and peppers are all another type of simple fruit (a type called true berries). They have fleshy walls and are very watery inside—think of how watery a ripe tomato is! Another tasty group of simple fruits includes apples and pears (these are known as pomes). We said that there are actually three general fruit groups, with simple fruits being only one of these groups. Aside from simple fruits, the two other general fruit groups are "aggregate fruits," which include raspberries, and "multiple fruits," which include pineapples. Do you think that fruits that belong to the same group will have a similar number of seeds, or do you think that within a group there will be fruits with different numbers of seeds?

How do some of your favorite fruits produce seeds? What strategies do they use? Do they make many seeds, or just a few? In this science project 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 and Concepts

  • Fruit
  • Seed
  • Seed dispersal
  • Productivity
  • Simple fruits

Questions

  • What are some different kinds of fruit that you have encountered? Do you remember what their seeds looked like?
  • Why do you think some fruits might make more seeds than others?
  • What other seed dispersal strategies do plants use?
  • Do you think that fruits that belong to the same group will all have a similar number of seeds, or will there be big differences in the group?

Bibliography

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:

Have an adult help you do further research by visiting the following websites or reading the following books, which give information about fruits:

For help creating graphs, try this website:

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Materials and Equipment

  • Different fruits (at least 5 different types, and at least 3 fruits for each type of fruit). Try to include peppers, tomatoes, apples, and squash or cucumbers. These are all technically considered the "fruits" of their plants.
  • Knife
  • Cutting board
  • Paper towels (one for each type of fruit)
  • Adult helper
  • Lab notebook

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Experimental Procedure

  1. Go to the grocery store and pick out different kinds of fruit. Do not just stick to the traditional fruits, try some unique fruits as well.
    1. Some produce you might think are vegetables are really fruit!
    2. Try to include peppers, tomatoes, apples, and cucumbers or squash. Avoid seedless varieties of fruits.
    3. If you are very sensitive to peppers, use a mild pepper variety, such as a bell pepper.
    4. Tip: Bananas do have seeds, but they are very tiny, appearing as little black spots in the center of a banana slice. You can try to count them, but it is not recommended!
    5. Pick out at least three fruits for each type of fruit.
  2. In your lab notebook, make a list of all of the fruits you have chosen in a data table similar to Table 1 below.
    1. You will be recording the number of seeds, number of fruits counted, and the productivity for each type of fruit.
Type of Fruit Number of Fruits Counted Total Number of Seeds Productivity
(Number of seeds/fruit)
Bell Pepper   
Tomato   
Apple   
Zucchini   
etc...   
Table 1. In your lab notebook, make a data table like this one to record your data in.
  1. Begin to dissect your first fruit. Have an adult carefully use the knife on the cutting board to cut open the fruits.
    1. Peppers and their 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.
  2. Remove the seeds from the fruit and put them on a paper towel.
    1. In the fruit, are the seeds arranged in a certain pattern?
    2. Remember that a "pit" is the same as a seed, and will be found in "stone fruits" like cherries, peaches, nectarines, plums and apricots.
    3. Strawberry seeds are on the outside of the fruit, so pick them off using your fingernail or a toothpick.
    4. If you are dissecting a cucumber or squash, instead of removing the seeds you can try cutting the fruit lengthwise, counting the rows of seeds, and then slicing the fruit the other way to figure out how many seeds are in one row. Multiply these two numbers together to find out the total number of seeds in the fruit.
  3. Repeat steps 3-4 for all of one type of fruit. Keep all of the seeds from one type of fruit on one paper towel.
    1. In your data table, be sure to write down the number of fruits that you used to the collect seeds.
  4. When you are done removing the seeds from one type of fruit, count the total number of seeds on the paper towel. Write the number in your data table.
  5. Repeat steps 3-6 for each type of fruit. Use a new paper towel for each type of fruit.
  6. 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.
    1. To do this calculation, divide the total number of seeds by the number of pieces of fruit that you counted for each variety.
    2. For example, if you counted 20 seeds total in 5 grapes, then the productivity of a single grape would be 4 seeds per fruit.
    3. In your data table, write the productivity for each type of fruit.
  7. Make a graph to show the number of seeds per fruit, or each type of fruit's productivity. You can make a graph by hand or use a website like Create a Graph to make a graph on the computer and print it.
    1. A bar graph works best for this type of science project. Put the number of seeds per fruit on the left side of the graph (Y-axis) and make a bar for each type of fruit. Make the bar go up to the correct number of seeds per fruit. Remember to label each bar of your graph with the correct type of fruit.
  8. Which fruits had the most seeds? Which fruits had the least seeds? Did similar types of fruits produce similar numbers of seeds? Was the number of seeds from the different types of simple fruits all similar, or were there a lot of differences?
    1. How do seeds from different types of fruit look similar or different? In each fruit, were there similar patterns in which the seeds were arranged?
    2. Tip: You may want to re-read the Introduction in the Background tab to help you remember what the different types of fruits are.

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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 seedless fruits. Dissect the fruits and look for seeds. Are these varieties completely 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?
  • Can the appearance of a plant's seed give you clues as to how it is dispersed? Other than being dispersed by animals eating their fruits, plants also disperse seeds using wind, water, or animals in other ways. 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.

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