TOPIC 7: PLANT ADAPTATIONS Flashcards
Photosynthesis
process where energy from the sun is used to transform CO2 into
carbohydrates (simple sugars) and O2
Chlorophyll (light absorbing pigment) traps light energy → synthesizes ATP →
this energy drives CO2 → O2 + sugars
Where does photosynthesis take place?
takes place in specialized cells (mesophyll cells) in the leaf
rubisco
enzyme that catalyzes part of the photosynthetic reaction
- makes rxn happen after
- more of it= faster rxn
- Respiration:
: in the mitochondria of cells (plant & animal) - carbohydrates are broken down to generate energy (ATP), releasing CO2
Net Photosynthesis
Plants both use and produce CO2 and the difference in the rates of these two processes
is:
Net Photosynthesis = Photosynthesis – Respiration
* (= carbon uptake – carbon loss)
stomata
openings in the leaf thru which CO2 diffuses into the leaf
transpiration
- CO2 enters: atmosphere»_space; leaf
- Water leaves: atmosphere «_space;leaf
What essential resources do plants require?
light, CO2, water, nutrients
Leaf tissue
- photosynthesis (uptake of CO2)
Stem tissue
- structural support (gain access to light)
Root tissue
- water and nutrient uptake from the soil
Compare the adaptations that plants have at the tree top vs tree bottom
- Tree Top (direct sunlight)
- smaller, thicker leaves
→ reduces water loss in direct sunlight - Tree bottom (shade)
- larger, thinner
→ increases photosynthetic rate in shade
Plants are either…..
to low light (shade-tolerant) or high light (shade-intolerant)
Shade-tolerant (low light):
In shade: photosynthesis is limited by availability of light
* lower production of rubisco in leaf tissue (do not expend energy producing high amounts of rubisco)
Lower maximum photosynthetic rate
How do shade tolerant plants compensate?
- higher production of chlorophyll (light absorbing pigment)
- higher leaf surface area
- higher growth of leaves than roots
- increase the photosynthetic surface area to offset the decrease in
photosynthetic rate (due to lower amount of rubisco)
What happens to the plant growth if you put a shade intolerant plant in the shade vs if you put a shade tolerant plant in the sun?
- Shade-intolerant - high growth rates under sunlight, but low rates in shade
- Shade-tolerant - grow similarly under sunlight and shade
- cannot increase growth dramatically in sunlight because limited by rates of
photosynthesis (lower concentration of rubisco)
Mountain Avens
Flowers track the movement if the sun
- Parabolic formation of petals concentrate light to maintain a constant temperature of
25⁰C.
- Keeps sex organs of the plant warm and creates a microhabitat favourable for
pollinators
Mountain Avens
Flowers track the movement if the sun
- Parabolic formation of petals concentrate light to maintain a constant temperature of
25⁰C.
- Keeps sex organs of the plant warm and creates a microhabitat favourable for
pollinators
Plants vs. Temperature
Photosynthesis and respiration respond directly to variations in temperature
* As temperatures rise above 0, rates of both respiration and photosynthesis increase
* A maximum rate of photosynthesis and respiration occur at different points
* Proteins denature and both processes stop eventually
What must a leaf do to maintain optimal levels of photosynthesis?
must exchange excess heat with the
surrounding environment
Heat loss by convection
transfer of heat to a moving fluid body (ie. Wind)
Heat loss by conduction
- Heat moving from a warmer to a cooler body
Heat loss by evaporation
Evaporation causes a loss of heat energy and temperatures drop due to
evaporative cooling
Pubescence
small light-coloured hairs that line a leaf’s surface and reflect
- Less heat obtained from solar radiation
- Also creates a insulative boundary later
