1 / 29

Unit 2 Biology

Unit 2 Biology. Plant Behaviour. WEEK 3: Plant Behaviour. LEARNING OUTCOMES By the end of this week, you should: Have an understanding of the behavioural adaptations in plants. Recognise the importance of behaviours to the survival of individuals and groups. Plant Behaviour.

asabi
Download Presentation

Unit 2 Biology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 2 Biology Plant Behaviour

  2. WEEK 3: Plant Behaviour LEARNING OUTCOMES By the end of this week, you should: • Have an understanding of the behavioural adaptations in plants. • Recognise the importance of behaviours to the survival of individuals and groups.

  3. Plant Behaviour • Plant growth and development is influenced by internal and external factors • Internal factors – hormones e.g. auxins • External factors – (name 4 examples) Watch the Mythbusters clip “Talking to Plants”

  4. How do plants respond? TROPISMS: • A directional growth response of a plant to an environmental stimulus • e.g. light, water, gravity, touch, day length, water. • Positive tropism: plant growing towardsthe stimulus. • Negative tropism: plant growing away from stimulus.

  5. What does it mean? Gravitropism • Look at the following tropisms and discuss with the person next to you what they might be responses to: Hydrotropism Photoperiodism Chemotropism Phototropism Thigmotropism Galvanotropism Heliotropism

  6. What is happening here? • Which stimulus made these plants grow this way? • How did the plants do it? • Why would they grow this way? • These plants are not necessarily moving in a certain direction, but growing in that direction.

  7. Tropisms • Phototropism: growing towards the light. • Geotropism: responding to gravity • Negative geotropism: a shoot grows upwards. • Positive geotropism: a root grows downwards. • Photoperiodism: responding to changes in day-length.

  8. Plant Hormones - Auxin • Plants have hormones that control their growth and development. • Auxin is produced in the coleoptile (the growing tip of the shoot). • Where present, auxin causes elongation of cells. • When affecting growth in a shoot: • Receptor: tip of shoot • Effector: growing region below tip

  9. Auxins and phototropism • Auxinis deposited on the ‘dark side’ of the growing shoot tip (away from the light source). • Therefore cells on the darker side grow faster. • Uneven growth = bending of tip.

  10. 1 2 3

  11. Draw and label this: Now explain what is happening to the person next to you.

  12. Phototropism experiment

  13. Can you explain this? • The shoot did not bend because the tip was removed and this is where the auxin is produced. • The shoot did not bend because the tip was covered and so was not affected by the light. • The shoot did bend because it was covered by a transparent cap and so the light could affect the tip. • The shoot did bend because auxin is not produced in the base of the shoot. • The shoot did bend because the auxin can diffuse through the gelatin block. • The shoot did not bend because auxin cannot pass through the mica. 2 3 5 6 4 1

  14. What is happening here?

  15. How do plants always grow the right way up?

  16. Geotropism What part of the plant might respond to a positivegeotropism? • Geotropism (also called gravitropism) is a plant response to the Earth's gravitational field. • Roots are positively geotropic because they grow ‘towards gravity’ (down). • Shoots are negatively geotropic because they grow ‘away from gravity’ (up). What part of the plant might respond to a negativegeotropism?

  17. Geotropism What are the advantages of negative geotropism in tall shoots? Negative geotropism is advantageous because: • Leaves and flowers are lifted off the ground. • The plant can better compete for light and CO2. • Flowers brought into good position for wind and insect pollination. • Seed dispersal is more effective.

  18. Geotropism Positive geotropism is advantageous because: • Roots penetrate the soil. • This is the source of water and mineral salts for the plant. • It also anchors the plant. What are the advantages of positive geotropism in roots?

  19. Auxins and Geotropism • When present in a root, auxininhibits elongation – they grow slower. • So it is the upper part of the root that grows faster so the root will bend downwards towards gravity.

  20. What about the shoots? • In a horizontal seedling, auxin accumulates along the lower horizontal part of the shoot causing the cells in that part to grow faster. • Hence, the shoot turns upwards, away from gravity.

  21. EXPERIMENT: Geotropism What is going to happen?

  22. Can you explain this? • What happens to a plant when it falls on its side? • Explain it to the person next to you. • Draw a diagram – include where the auxin works. Extension:

  23. Which tropism?

  24. Other Tropisms • Thigmotropism – response to touch/contact. • Circadian rhythm – like a biological clock, an activity that follows a 24-hour cycle. This movement is called nasticmovement (not influenced by direction of stimulus). • Heliotropism – solar tracking (following the sun). • Photoperiodism – response to periods of light and dark. Flowering is affected by this.

  25. Short or long day plant?

  26. What is going on here?

More Related