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VCE Biology Plants Responding to the Environment
- 1. VCE BIOLOGY www.drlakshmisharma.com Dr Lakshmi Sharma NO LIMITS TO LEARNING! BELIEVE & YOU CAN ACHIEVE! Plants Responding to Environment
- 2. RESPONDING TO THE ENVIRONMENT • Plants do not have specific receptors. • Hormonal response to stimuli, slow.
- 3. How do Plants Respond to the Environment? 5 Minutes to Discuss & Answer in Pairs
- 4. How do plants respond to the environment The environmental stimulus causes a sensitive cell to produce a particular hormone
- 5. Stimuli Two types of Stimuli: Chemical Physical Can you explain the difference between these stimuli ?
- 7. Types of Stimuli Geotropism Reaction to gravity
- 8. Types of Stimuli Geotropism Reaction to gravity Phototropism
- 9. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths
- 10. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism
- 11. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods
- 12. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism
- 13. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture (water)
- 14. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism
- 15. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism
- 16. Types of Stimuli Geotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch
- 17. Types of StimuliGeotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch Thermotropism
- 18. Types of StimuliGeotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch Thermotropism Reaction to temperature
- 19. Types of StimuliGeotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch Thermotropism Reaction to temperature Chemotropism
- 20. Types of StimuliGeotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch Thermotropism Reaction to temperature Chemotropism Reaction to chemicals
- 21. Types of StimuliGeotropism Reaction to gravity Phototropism Reaction to light and different wavelengths Photoperiodism Reaction to the length of light and dark periods Hydrotropism Reaction to moisture gradient (water) Thigmotropism Reaction to touch Thermotropism Reaction to temperature Chemotropism Reaction to chemicals 2 categories of stimuli; Chemical & Physical Can you assign?
- 22. SENSING LIGHT Some wavelengths effect plants development Blue wavelength (350-500nm) causes growth the pigment CAROTENE produces a hormone in response Orange-red (620-670nm) induces flowering and stem elongation Far red (710-750nm) inhibit, flowering and stem elongation
- 23. How would different light affect the same plant?
- 24. What do you notice ?
- 25. PHOTOPERIOD (day/night cycle) & FLOWERING Short day plants require long nights to trigger flowering. Late summer, autumn or winter Long day plants. Flower if nights are shorter. During summer or spring Neutral plants unaffected by day length
- 26. PLANT MOVEMENTS Presence and absence of light. At night plants fold up their leaves and flowers. Solar - Leaves twist on their stalk in response to light Nodding & Contraction Pea seedlings move side to side ethylene thickens & bends shoot – push through the soil Sleep Movements
- 27. Rapid Response Carnivorous plants rely on rapid movements to trap prey. Venus Fly Trap Responds to the fly’s touch (stimulus) in specialised leaves, snapping them shut.
- 28. Plants survive harsh winters and droughts by: Seed dormancy Bud dormancy Vernalisation
- 29. Seed Dormancy Triggers: Winter (Cold) Ready to grow in spring Desert plant seeds non-germination until water washes away the seed development inhibitor (ABA) Some Australian native plants need smoke to germinate WA – Wreath Lechenaultia
- 30. BUD DORMANCY Plants become dormant in autumn, ready for winter (due to ABA-env. change) Stimulus: decreasing temperature Response: Nutrients retreat back into stems and roots Loss of chlorophyll in leaves
- 31. VERNALISATION Vernalisation:period of winter cold that stimulates flowering Δ Some seeds need it for germination. e.g. snow gums. Cold Induces flowering in bulbs e.g. Crocuses Biennials – after second year require vernalisation for flowering, e.g.sugar beet
- 32. HOPE YOU ENJOYED THE LESSON ! ANY QUESTIONS ???!
Editor's Notes
- Instead their response to stimuli is hormonal, so it can take a while for the chemical signal to reach its target cells.
- Plants don’t just react to light, they react to the specific wavelengths that make up white light. Blue light, will cause plant growth, they think it triggers the pigment CAROTENE which will produce growth promoting hormones. Orange to red light will switch on flower and stem growth, while far red light will switch off flowering and stem elongation. Enzymes inducing and inhibiting?
- Tested this by growing plants in rooms with only blue light, only green light etc. Green plants will grow slower or not at all under green light because it’s the only wavelength that plants don’t use.
- Tested this by growing plants in rooms with only blue light, only green light etc. Green plants will grow slower or not at all under green light because it’s the only wavelength that plants don’t use.
- we separate the plants into those that flower on short days and those that flower on long days, but its actually the amount of dark hours that the plant is reacting to. But this was figured out long after the plants were named so it stuck. If there is a long night, short day plants will flower, when do we have shorter days? so during winter And if there is a short night, like in summer long day plants will flower Some plants don’t care about the night length and will flower on a different schedule, these are called neutral plants
- Plants react to the presence and absence of light, you saw in one of the video clips last lesson that the plants leaves curled up during the night. Flowers will also fold up, and stomata, the openings in the leaf that allow water and gases in and out will, in most plants shut at night. These are a plants sleep movements. In animals the day/night cycle is called the CIRCADIAN RHYTHM, lots of genes involved with names like “clock” and “time” They all do this by changing the internal fluid pressure of the cells. Stomata have guard cells on either side that act like gates, when there is lots of fluid in these cells they will expand, closing the stomata. When the fluid leaves the cells they will contract and open the stomata again. By controlling which cells are expanding and contracting the plant can open and close its flowers and leaves.
- For the venus fly trap the flys touch is the stimulus that triggers the leaves RAPID RESPONSE this combines the internal fluid pressure and a lot of energy to quickly snap shut the specialised leaves. So if you keep poking it, it will eventually stop reacting as it needs to make more energy.
- Plants have adapted ways to cope with their environments harsh winters or droughts. Some of these involve dormancy, waiting for the right trigger to tell the plant that conditions are or are about to be right for growth. 3 plant survival mechanisms are: Seed dormancy Bud dormancy And vernalisation
- The dormant seed will know conditions are good because of various triggers. Temperature is the main trigger, having been cold for the last three months the seed knows that spring is coming. Desert plants need water so they will only grow after sufficient rainfall, the seed needs water to wash away the abscisic acid which has been stopping the seed from growing. Some seeds grow better after exposure to smoke, bushfires, controlled burning. Pg 274.
- Bud dormancy is when the grown plant is getting ready for winter. So at the moment we can see lots of plants becoming dormant. This is a reaction to the lower temperatures. The leaves loose their chlorophyll, the chemical that makes them green. And the nutrients retreat back into the stem and roots of the plant So the leaves change colour and fall. Which growth hormone is involved in this? Abscisic acid
- Vernalisation is the plants response to temperature, promoting flowering or growth at all stages of the plants life cycle So winter plants will flower. So seeds get ready for germination, this is why wheat is planted in autumn And new seedlings will flower for the first time.