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Chapter: Biology laboratory Practicals: Biology Activities

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Investigate the Effects of Phototropism

Investigate the Effects of Phototropism
Tropic movement is the directional movement of a plant in response to an external stimulus. Phototropism is the growth of plant shoots towards light.

Movement

Movement is the change in the position of an organism or a part of an organ-ism. There are two types of movement: locomotion and growth curvature. Animals, protoctista, and some bacteria use locomotion to move their whole body from place to place. Plants use growth curvature to respond to stim-uli such as light, gravity and important chemicals needed for growth and survival.

 

These activities are conducted well in small groups over a week.


Investigate the Effects of Phototropism

Tropic movement is the directional movement of a plant in response to an external stimulus. Phototropism is the growth of plant shoots towards light.

Learning Objectives

To carry out experiments to investigate the e ect of phototropism on plants.

Materials

Maize grain, 2 pots or containers, cotton wool, and 2 boxes.

Preparation Procedure

1.           Make a hole in one of the boxes on the side.

2.            Germinate maize grains by placing them into a container with wet soil.

Activity Procedure

1.           Cover the maize seedlings with the two boxes, one with a hole and one without a hole.

2.           Leave the covered plants for about 2-3 days.

3.           Uncover the boxes and observe the direction of the shoot in the two separate plants.

Results and Conclusion

The plant covered by the box with no light source will grow upwards. The plant covered by the box with the hole will grow towards the light.


Figure 6.10: A diagram of a phototropism activity.

Clean Up Procedure

1.           Collect all used materials, cleaning and storing items that will be used later. No special waste disposal is required.

Notes

The investigation shows that plant stems grow towards a light source. This shows that they are positively phototrophic. This tropism enables plant leaves to receive the maximum amount of light for photosynthesis.


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