Positive tropism: A positive tropism is
growth towards the stumulis
Negtive tropism: A negative tropism is growth
away from the stimulus
There are three different types of tropisms
Geotopisms: Growth in respons to gravity
Phototropism: Growth in response to light
Hydrotropism: Growth in response to water
What are auxins?
Auxins are a group of hormones that are found in plants
They are normally found in the tips of shoots and roots or
have diffused therefor being found in over parts of the plant
They change the elongation in plant cells controlling the direction of growth
How do auxins make tropisms?
Plants will grow in a certain direction according to the
position of the light in order for photosythesis to take
place
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?
They are used as weedkillers that are not
harmful to surrounding plants or animals
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
Hormones can also be used to ripen fruit or induce flowering
when needed and speed up or slow down the growth
Some unpollinated plants are treated so they grow
fruit without seeds
Experiments to show the effect of tropisms
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.