Plant Structures and their functions Flashcards
Where does photosynthesis take place?
Chloroplast
What is the function of the chlorophyll?
Absorbs light
What type of reaction is photosynthesis?
Endothermic (takes in energy)
What are the three limiting factors in photosynthesis?
Light intensity, the concentration of carbon dioxide and temperature
Function of the waxy cuticle
- Top of the leaf
- Thin layer that prevents water loss
Function of the upper epidermis
- Top of the leaf
- Transparent and allows light to pass through to the palisade layer
Function of the palisade layer
- Packed with palisade leaf cells
- Filled with chloroplast
- Near the top of leaf to get as much light
Function of the spongy mesophyll layer
- Middle of the leaf
- Contains air spaces to increase the rate of diffusion of gases in and out of the cell
Function of the lower epidermis layer
- Bottom of the leaf
- contains alot of stomata
Function of the stomata
- tiny pores on the surface of the leaf
- allows carbon dioxide and oxygen to diffuse directly in and out of the of leaf
Function of the guard cells
- The change size to control the size of the stomata
Function of the root hair cell
- Take in minerals by active transport and water by osmosis
- Gives the plant a large surface area for absorbing water and minerals from the soil
- Large mitochondria from respiration for active transport
Function of the phloem
- Transport food (sugars). This called translocation
Adaptations of the phloem
- Made of living cells in a columns with small pores in the end walls
- Move in both directions
Function of xylem
- Transport water and minerals. This called transpiration
Adaptations of the xylem
- Made of dead cells joined with no cell walls between them
- The walls around are strengthened with lignin
- The move in one direction from roots to leaves
How does transpiration work?
- By evaporation and diffusion
- The water lost is drawn up from the rest of the plant through the xylem vessels
- This is known as the transpiration stream
Light intensity formula
1/(dxd)
Explain light intensity being a limiting factor
- At first light intensity is directly proportional to the rate of photosynthesis until a certain point
- When the line on the graph plateaus light is no longer the limiting factor
Explain carbon dioxide being a limiting factor
- As the carbon dioxide increases the rate of photosynthesis also increases until a certain point
- When the line plateaus carbon dioxide is no longer the limiting factor
Explain temperature being a limiting factor
- If the temperature is too low the enzymes for photosynthesis will work slower
- If it is too hot the enzymes will denature
- This happens around 45 degrees
What are the factors affect transpiration?
- Light intensity
- Temperature
- Air Flow
- Humidity
How can you estimate transpiration rate?
Potometer
How can you investigate the effect of light intensity on the rate of photosynthesis?
- Add sodium hydrogen carbonate to pondweed in water to make sure the pondweed gets enough carbon dioxide
- Attach gas syringe
- Put light sources at a specific distance
- Leave for a certain amount of time
- Repeat with different distances.
What are auxins?
Plant hormones which control growth at the tips of shoots and roots
What do the auxins do?
They dissolve in the solutions of the cell. They then diffuse backwards along the shoots and the roots.
What does auxins do at the roots?
Inhibit growth
What does auxins do at the shoots?
Stimulate growth
What is it called when a plant responds to light?
Phototropism
What side will the auxins accumulate?
They will either go on the shaded side or the lower side.
What are the shoots positively and negatively?
They positively phototropic and negatively gravitropic
What does it mean to be positively phototropic?
Grow towards the light
What does it mean to be positively gravitropic?
Grow towards the gravity
What are the roots positively and negatively?
They are negatively phototropic and negatively gravitropic
What causes plants to grow towards the light?
Auxins accumulate on the shaded side. Therefore the cells on the shaded sides grow faster which causes the plant to bend to the light.
What causes the roots to curve downwards?
If exposed to light the auxins will accumulate on the lower shaded side and in the roots auxins inhibit growth which them causes the upper side to grow faster
What are the 3 uses of auxins?
- To grow plant clones
- To grow plant cuttings
- To kill weeds
How does auxins kill plants?
By adding a lot of auxins it can disrupt the plants growth patterns
What are 3 uses of gibberellin?
- Controlling dormancy
- Inducing Flowering
- Grow larger fruits
How does gibberellin control dormancy?
Induces germination at certain times of the year when plants dont have the right conditions to grow
How does gibberellin induce flowering?
Flowers need certain conditions to grow but gibberellin allows flowers to grow on demand which can allow farmers to grow bigger and more flowers
How does gibberellin help growing larger fruits?
It is useful for seedless fruits that naturally dont grow as seeded fruits. Gibberellin allows the fruits to grow well.
What is the used of the hormone ethene for plants?
Stimulate the ripening of fruits by stimulating a hormone.
