Tropisms

Tropisms

What are tropisms?
1. A tropism is growth in response to a stimulus
What are negative and positive tropisms?
1. Positive tropism: A positive tropism is growth towards the stumulis
2. Negtive tropism: A negative tropism is growth away from the stimulus
There are three different types of tropisms
1. Geotopisms: Growth in respons to gravity
2. Phototropism: Growth in response to light
3. Hydrotropism: Growth in response to water
What are auxins?
1. Auxins are a group of hormones that are found in plants
2. They are normally found in the tips of shoots and roots or have diffused therefor being found in over parts of the plant
3. They change the elongation in plant cells controlling the direction of growth
How do auxins make tropisms?
1. Plants will grow in a certain direction according to the position of the light in order for photosythesis to take place
2. Plants have developed a stimulus known as tropisms in order to make sure they grow towards sources of light and water
How are plant hormones used in agriculture?
1. They are used as weedkillers that are not harmful to surrounding plants or animals
2. To produce new plants from cuttings as farmers are able to use 'Hormone Rooting Powder' so cut stems can develop roots and grow into clones of their parent plant
3. Hormones can also be used to ripen fruit or induce flowering when needed and speed up or slow down the growth
4. Some unpollinated plants are treated so they grow fruit without seeds
Experiments to show the effect of tropisms
1. Cress experiment expected outcome: The cress responded to the stimulus reasonable well as the shoots moved towards the light gradually when it was on the left. More auxin was produced on the side with less light shining on and so the plant grew more on that side and bent towards the light. The roots also responded quite well to the gravity and geotropism.

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