B11: Plant Hormones and Response Flashcards
What is phototropism?
A plants response to light
What is geotropism
A plants response to gravity
Where is auxin produced?
In the tips of plant shoots and roots
Which part of the shoot is more sensitive to light?
The upper or lower part?
The upper part
How do shoots use auxin to grow towards light?
Auxin is produced in the tips of the shoots, light causes auxin to concentrate on the darker side of the shoot tip. Auxin now spreads down the shoot, so cells on the darker side grow faster than the cells on the lighter side, causing the shoot to grow towards the light.
What is the effect of Auxin in the shoots?
Auxin triggers growth in the shoots
How does Auxin affect the roots of a plant?
Auxin is produced in the root, but gravity causes auxin to concentrate on the lower side. As auxin inhibits growth in the roots, the lower side now grows more slowly than the upper side, causing the roots to grow towards the force of gravity.
What does Auxin do in roots
It inhibits growth
How are Giberellins useful for plants?
They are important in starting seed germination
How is Ethene important for plants?
They are important in controlling cell division and the ripening of fruit
Describe the 3 main uses of Auxins
- Weedkillers in gardens
- Rooting powders
- Promoting growth in tissue culture
Describe uses of Giberellins
- Can be used to end seed dormancy (force a seed to germinate early)
- Trigger plants to flower
- Make fruits grow larger
Describe the use of Ethene in the food industry
Foods (e.g. bananas) are usually harvested before they’re ripe, and are then transported long distances and stored.
- Ethene is used to trigger the bananas to ripen just before they’re sold
What is a tropism?
The response of a plant to a specific stimulus
Explain the results for the “Plant response to light intensity” practical
The height of the seedlings are similar for full and partial sunlight, as chlorophyll is very efficient at absorbing light energy, so plants don’t need full sunlight to grow. Plants grow towards the light due to phototropism. The seedlings in the dark have grown the tallest as seeds usually germinate underground, and grow rapidly to reach the light. Keeping seedlings in the dark causes them to grow rapidly to reach light. Also, the leaves left in the dark are small and yellow as a result of using up all energy stores, and can’t carry out photosynthesis in the dark
