Topic 6 - Plant Structures and Their Functions Flashcards
How do plants generate food?
Via photosynthesis
Is photosynthesis an exothermic or endothermic reaction?
Endothermic, as it takes in energy (heat energy from the sun)
In what plant structure does photosynthesis happen?
Chloroplasts
What is the balanced symbol equation for photosynthesis?
6CO2 + 6H2O + Light Energy + Chlorophyll = C6H12O6 + 6O2
Describe a method to test the effect of light intensity on the rate of photosynthesis:
- Put pondweed in a beaker with water and sodium hydrogencarbonate
- Connect gas syringe to the top of beaker through a cork
- Set a light source at a set distance away
- Measure the distance moved by the gas syringe due to oxygen bubbles
- Repeat for different distances
- Plot a graph for the results
What are the three limiting factors for photosynthesis?
- Light Intensity
- Carbon Dioxide
- Temperature
What is the inverse square law?
As the distance increases, the light intensity decreases by a factor of x squared
Describe the three graphs for limiting factors of photosynthesis:
- Light Intensity: Linear, then flat
- Carbon Dioxide: Linear, then flat
- Temperature: A curve around 37°C
How does light intensity affect the rate of photosynthesis?
It is needed for photosynthesis, so if it is lower, then the rate will be slower
How does carbon dioxide affect the rate of photosynthesis?
It is a reactant of photosynthesis, so if it is lower, then the rate will be slower
How does temperature affect the rate of photosynthesis?
At low temperatures, the enzymes do not have the activation energy, but at high temperatures, they become denatured
What do root hairs do?
Take in minerals and water, generally by active transport
What do phloem tubes transport?
Food
What do xylem tubes transport?
Water (UP)
What is transpiration?
The loss of water from a plant
What causes transpiration to happen?
Evaporation and diffusion
What are stomata needed for?
Gas exchange
How do guard cells affect whether stomata are open or closed?
If the guard cells are turgid, the stoma is open
If the guard cells are flaccid, the stoma is closed
What environmental factors affect transpiration rate?
- Light Intensity
- Temperature
- Air Flow
Give examples of how leaves are adapted for photosynthesis and gas exchange:
- Leaves are broad
- Palisade layer has lots of chloroplasts
- Waxy Cuticle
- Upper epidermis is transparent to allow light through
- Air spaces above the stomata
What are auxins?
Plant growth hormones that control growth at the tips of shoots and roots
Finish the sentence: Shoots are positively ___ and negatively ___
Phototropic
Gravitropic
Finish the sentence: Roots are positively ___ and negatively ___
Gravitropic
Phototropic
What are commercial uses of plant hormones?
- Selective weedkillers
- Growing from cuttings
- Controlling ripening
- Controlling flowering
- Producing seedless fruit
- Controlling seed germination
What is the plant hormone that controls ripening?
Ethene, as it causes the fruit to ripen
Why do stores use ethene for their produce?
Because it ensures that the fruit becomes ripe whilst on the shelves, and ensures that they can sell that fruit all year round, depsite it only being grown for 2 months a year!
