Abstract

Objective

The goal of this experiment is to investigate how the size and shape of fruits or seeds influence their ability to be dispersed by wind.

Introduction

dry seeds scatter

from my hand into the wind

one clings

as if to say there is in me

something yet to be

— Jeanne Emrich

Dispersal of seeds is important for the continued survival of a plant species. If plants grow too closely together, they compete for light, water, and nutrients. Seed dispersal allows offspring to be spread over a wide area and decreases the competition between offspring.

Seeds are dispersed in several different ways. In flowering plants like apple trees, one or more seeds are housed within a fruit. The fruit is the portion of the apple that we eat. Sweet fruit, like apples, are eaten by animals that disperse the undigested seeds. Some fruits can be carried by water, like the coconut. Burdock fruits have hooks that attach to an animal's furry coat. Dandelion fruits are suspended from feathery "parachutes" that are carried on the wind. The fruit of maple and ash trees have wings that let them float on air.

In this experiment, you will investigate how the size and shape of fruits or seeds influence their ability to be dispersed by wind. You will design your own fruit or seed and measure two important qualities that enhance its ability to disperse in the wind: distance traveled and time aloft.

From "Sailing Seeds: An Experiment in Wind Dispersal," by Steven K. Rice, used with permission.

Terms, Concepts, and Questions to Start Background Research

Terms

• seed
• fruit
• wind dispersal
• water dispersal
• animal dispersal

Concepts

• the relationship between seed shape, mass, size and dispersal method
• the relationship between fruits and seeds

Questions

• What are the advantages and disadvantages of each type of dispersal?
• Is a fruit or a seed more likely to be dispersed by the wind?

Bibliography

• Original Online Lab:
  Sailing Seeds: An Experiment in Wind Dispersal
  http://mcintosh.botany.org/bsa/misc/mcintosh/dispersal.html
• Great Pictures and General Information on Seed Dispersal:
  Blowing in the Wind: Seeds and Fruit Dispersed by Wind
  http://waynesword.palomar.edu/plfeb99.htm
• Video and Pictures of Seed Dispersal:
  http://mbgnet.mobot.org/bioplants/seed.html
• General Plant Information:
  Stern, Kingsley R. 2000. Introductory Plant Biology, 8th ed. McGraw Hill, Dubuque, IA.

Materials and Equipment

• fruit and/or seed examples from sunflowers, dandelions, maple trees, coconuts, apples, peas, nuts
• supplies to construct artificial "fruit" or "seeds" (paper, tape, scissors, glue, pipe cleaners)
• window or large fan
• meter stick or tape measure
• stop watch
• marker
• an assistant
• a video camera (not required, but it may help to analyze the data and enrich your observations)

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Experimental Procedure

1. Investigate different types of fruits and seeds. Take notice of fruit or seed shape and size and research how each is dispersed. Is there a relationship between the structure of the fruits and seeds and how they are dispersed? Record your observations in your lab notebook.
2. Experiment with several sunflower fruits (commonly called "sunflower seeds") by constructing different wind dispersal mechanisms for the fruit. Focus on what shape and size will allow your fruit to travel the farthest and stay aloft for the longest amount of time.
3. After you have made several different models, evaluate each fruit's dispersal characteristics according to the following procedure:
   • Set up the fan on a table blowing horizontally across the room.
   • Establish a standard drop site above the fan and set up a tape measure along the floor beneath the fan.
   • If you are using a video camera, set up the camera to record the complete flight.
   • Each fruit model should be dropped at least four times from the same point above the fan. Experiment with your set-up to find the best height, then use that height consistently for all trials.
   • Record the time aloft and the distance traveled for each trial.
   • Average the time aloft and distance traveled for each fruit.
4. Graph your results.
5. Is there a correlation between maximum time aloft and the distance each fruit traveled?
6. Example Data Table:

   Seed Dispersal Example Data Table
   		Time Aloft (s)	Distance Traveled (cm)	Average Time Aloft (s)	Average Distance Traveled (cm)
   Control #1 (no wings added)	Trial #1
   	Trial #2
   	Trial #3
   	Trial #4
   Model #1	Trial #1
   	Trial #2
   	Trial #3
   	Trial #4
   Model #2	Trial #1
   	Trial #2
   	Trial #3
   	Trial #4

Variations

• Experiment with different masses or shapes or sizes of seeds to determine the best shaped seed for wind dispersal.
• Focus on a different mode of dispersal (water) and conduct an experiment to see what size and shape of fruit or seed is dispersed best by water.

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

Credits

La Né Powers

"Sailing Seeds: An Experiment in Wind Dispersal," Steven K. Rice, Amy Russell, and the Botanical Society of America

Last edit date: 2006-01-17 18:13:34