The Effects of Light and Temperature on the Growth and Development of Plants 

Robinson, Minnie L.                 Fenger High School
                                    11220 South Wallace Ave.
                                    Chicago, IL 60628
                                    1-312-821-2830

Objectives

1. To show how visible light constitutes only a small part of the spectrum of radiant 
   energy. 
2. To show how light can be separated into a variety of colors if passed through a 
   prism. 
3. To show that certain colors correspond to different wavelengths of the light 
   present. 
4. To show how certain wavelengths are reflected by plant pigments and others are 
   absorbed. 
5. To show that when plants are grown in different wavelengths and temperature 
   variations,the size,color and the length of their growth processes are affected. 

Equipment and Materials

overhead projector             vermiculite
Early Scarlet Radish Seeds     plant food
two thermometers               water
12 mini peat plant pots        two quart bottles    
two trays or containers        graph paper
labels                         small metric ruler
Polaroid Camera                green and red transparency paper 
12 medium peat plant pots      clear transparency sheets 

Recommended Strategies

Review light waves using a prism. Show how light waves can be separated with a prism. 
Show the different colored light waves. Show how some of the colors can be reflected 
and others can be absorbed. Encourage students to list the size, color, height, 
number of leaves, etc., from plant samples given. 

Using five groups of students, distribute two samples of experimental plant samples 
to each group. Also, distribute data sheets to each group. Students  will observe and 
record observations. Plot the temperature and growth patterns on a graph. 

Procedure for growing radish plants: Obtain 12 mini peat pots. Fill each pot to the 
halfway mark with vermiculite. Plant 10 radish seeds in each pot. Cover them with a 
thin layer of vermiculite. Water them thoroughly, using a diluted solution of plant 
food. Use red and green transparencies to cover two pots with red and two pots with 
green.  Use different shades of green and red transparencies to cover one with red 
and one with green.  Place three uncovered plants with the plants covered with the 
colored transparencies in the sunlight. Observe and record data on a daily basis. 
Place three uncovered pots in a dark room. Observe and record data daily.  Record 
data on the length, size, color, number of leaves and temperature for each 
experimental plant sample. 

Please note: Each experimental plant sample received a normal day without any  
manipulation of temperature. 

After 10 to 15 days of observation and recording data, place two of the plants 
covered with red transparency (plants grown in sunlight) in the darkness. Repeat the 
above procedure using plants covered with green transparency and plants not covered. 
Place two of the plants grown in a dark room in a sunlit environment. Observe and 
record data daily. Record data on the length, size, color, temperature and number of 
leaves for each experimental plant sample. 

Use photographs taken with a polaroid camera to show stages of development. Use 
graphs and charts to plot and make an analysis of the growth processes of plants' 
responses to visible light wavelengths in relationship to the temperature. 

Summary

Plants usually respond to light, touch and temperature.  They respond with leaves, 
flowers and fruit.  Visible light can be separated into different colors. Some colors 
reflect light while others absorb light.  A difference in light wavelengths will 
significantly affect the length, color, germination period, number of leaves, quality 
and quantity of fruit.  Darker shades of green and red transparency sheets produced a 
significant degree of change in plant development compared to lighter shades of red 
and green.  Temperature differences were slight and not controlled.  All plants 
received a normal temperature during the experiment. 

Note: all plants grown in the light received a full day of sunlight.  All plants 
grown in a dark room received a full day of darkness.  All plants were watered at the 
same time using the same amounts of water from the diluted plant food. All data was 
recorded at the same intervals.