Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science


Guide Index

Big Picture

City of Gold

Ways of the Wild

Mr. Cele's Garden

Fighting Malaria

The First People

Viewer Challenge
in the classroom
TEACHING GUIDES


SCIENCE SAFARI TEACHING GUIDE:
Mr. Cele's Garden


Africans have always relied on traditional medicines - even now they use a mix of old and new. Traditional healers once gathered the wild plants they needed to make healing remedies. But today they are often gathered by traders and many of the wild plants and trees are in danger of dying out due to the increasing demand. Botanists have become alarmed and are working with traditional healers like Mr. Cele to cultivate plants and save them from extinction.

Curriculum Links
Activity: Improving the Odds
Extensions


CURRICULUM LINKS

BIOLOGY

botany
taxonomy

EARTH SCIENCE

ecosystems

GENERAL SCIENCE

classification
plants

HEALTH

alternative medicines
herbs

LIFE SCIENCE

disease
medicine
plants


ACTIVITY: IMPROVING THE ODDS

As botanists and gardeners know, many factors play a role in plant growth. A supply of water and appropriate temperatures trigger an internal mechanism that causes a plant to begin to put down roots. The roots seek nutrients and the plant pushes toward the light with a stem and tiny energy-grabbing seed leaves.

OBJECTIVE

Investigate factors affecting seed germination and graph the results.

MATERIALS

  • mustard seeds (located in the spice section of grocery stores)
  • paper towels
  • 4 petri dishes
  • 4 small zipper-type plastic bags
  • small magnifying glass
  • 60-watt bulb power source
  • thermometer
  • boxes
  • ice chest ice
  • source of refrigeration
  • water

PROCEDURE

I. GERMINATION RATE

Work with a partner or in small groups.

  1. Cut four layers of paper towel to fit in each petri dish.
  2. Select 200 mustard seeds and divide them into groups of exactly 50 each. Use an index card to help separate and count seeds.
  3. For each dish, place two circles of paper towel in the bottom and spread 50 seeds evenly on top. Place two more paper towel circles on top of the seeds.
  4. Label the plastic bags 1, 2, 3, 4 and add your group name.
  5. Carefully saturate, but don't drench, the paper towels with water. Place each dish in a labeled plastic bag and seal.

II. PLACE EACH OF THE FOUR PACKAGES IN A DIFFERENT ENVIRONMENT

  1. Place the first in a closed box on the counter or desktop in the classroom. Measure and record the air temperature inside the box.
  2. Place the second in a closed box about two inches from a 60-watt bulb that is left on during the day (or in a warm spot in the room). Measure and record the air temperature in the box after the bulb has been on for 15 minutes.
  3. Place the third in an ice chest that contains a small amount of ice. Measure and record the air temperature inside the chest after it has been closed for 15 minutes.
  4. Place the fourth in a box to be placed in a refrigerator. Measure and record the air temperature inside the refrigerator.

III. OBSERVATIONS AND MEASUREMENTS

On a daily basis for the next three to four days:

  1. CAREFULLY open the packages and record the number of seeds that have germinated (split the seed coat) and sketch what you observe. Use the magnifying glass to provide details. Graph the results.
  2. Measure and record the temperatures of the different environments so you can compute an average daily temperature for each environment.
  3. At the end of the experiment record your observations for the entire experiment and address the following questions:
  • What percentage of seeds germinated in each collection?
  • Based on your results, what is the optimum environment for germination?


EXTENSIONS

  • How are botanists seen on Frontiers bringing back nearly extinct plant species?
  • Mustard plants belong to the family of crucifers. Find out what other plants belong to this family.
  • Some crucifers are being used in cancer research. Can you find examples of other herbs and plants being used as medicine?
  • Look up theWisconsin Fast Plants Program on the Web and locate where species of Brassicas grow in the world. Plot the sites on a map.









 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.