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Hormones (auxins and tropisms)

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Hormones (auxins and tropisms) Plants can respond to gravity, moisture and light. These responses are called tropisms - growth movements caused by auxins or 'plant hormones'. Auxins make some parts of a plant grow faster than others; the result may be that the plant bends towards or away from the stimulus. 1. Etiolation When a plant is left in the dark it puts all its energy into growing up to reach the light and makes very little chlorophyll. ...read more.


It does this because light coming from one side destroys the auxin in a leaf on that side. On the other side auxin makes the leaf grow faster. The result is that the leaves are turned towards the light for photosynthesis. We call this a positive phototropism. Diagram Of positive phototropism Roots grow down into the ground by a - towards gravity. The shoot from a seed underground positive geotropism can grow upwards, away from gravity, by a negative geotropism. ...read more.


You can buy geranium plants from a garden shop which may cost two or three pounds each. It is much cheaper to buy one and take cuttings from it. When your plant is growing nicely, you can cut a piece off it, dip it in rooting powder and then put it in some potting compost. The rooting powder will make it grow strong healthy roots. This is how the garden shop might produce their plants to sell to you. 3. Tropisms Tropisms are responses made by plants to stimuli such as gravity, moisture and light. * Tropisms can be towards a stimulus (positive tropism) * Tropisms can also be away from a stimulus (negative tropism) ...read more.

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