VCE BIOLOGY www.drlakshmisharma.com Dr Lakshmi Sharma NO LIMITS TO LEARNING! BELIEVE & YOU CAN ACHIEVE! Plants Responding to Environment
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VCE BIOLOGY
www.drlakshmisharma.comDr Lakshmi Sharma
NO LIMITS TO LEARNING! BELIEVE & YOU CAN ACHIEVE!
Plants Responding to Environment
RESPONDING TO THE ENVIRONMENT
• Plants do not have specific receptors.
• Hormonal response to stimuli, slow.
How do Plants Respond to the Environment?
5 Minutes to Discuss & Answer in Pairs
How do plants respond to the environment
The environmental stimulus causes a sensitive cell to produce a particular hormone
StimuliTwo types of Stimuli:
ChemicalPhysical
Can you explain the difference between these stimuli ?
Types of Stimuli
Geotropism
Types of Stimuli
Geotropism
Reaction to gravity
Types of Stimuli
Geotropism
Reaction to gravity
Phototropism
Types of Stimuli
Geotropism
Reaction to gravity
Phototropism
Reaction to light and different wavelengths
Types of Stimuli
Geotropism
Reaction to gravity
Phototropism
Reaction to light and different wavelengths
Photoperiodism
Types of Stimuli
Geotropism
Reaction to gravity
Phototropism
Reaction to light and different wavelengths
Photoperiodism
Reaction to the length of light and dark periods
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
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)
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
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
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
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
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
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
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
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 & PhysicalCan you assign?
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
How would different light affect the same plant?
What do you notice ?
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 plantsunaffected by day length
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
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.
Plants survive harsh winters and droughts
by:
Seed dormancy
Bud dormancy
Vernalisation
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
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
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
HOPE YOU ENJOYED THE LESSON !
ANY QUESTIONS ???!
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