Organisation - plants Flashcards
What are the tissues in leaves?
Waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, stomata, guard cells and mesophyll.
What does the waxy cuticle do?
Makes the leaf waterproof.
What does the upper epidermis do?
- Single layer of cells.
- Protects against water loss.
- Transparent to allow light to pass through.
What does the palisade mesophyll do?
-Tightly packed cells.
Lots of chloroplasts to absorb light for photosynthesis.
What does the spongy mesophyll do?
- Spherical cells.
- Lots of air spaces to allow gases to diffuse quickly.
- Large surface area-to-volume ratio to increase gas exchange.
What is the stomata?
Tiny openings on the lower surface of the leaf that allow gases to move into and out of the leaf.
What do guard cells do?
Control the opening and closing of the stomata.
How does the stomata control gas exchange and water loss from leaves?
- Allow the diffusion of carbon dioxide into the plant for photosynthesis.
- Allowing diffusion of oxygen out of the plant.
What is transpiration?
When water is lost through the stomata by evaporation and it pulls water up from the roots through the xylem.
What are transpiration leaves?
The constant movement of water up the plant.
What is the importance of transpiration?
- Provides water cells to keep them turgid.
- Provides water to cells for photosynthesis.
- Transports mineral ions to leaves.
What are the key structures of xylem?
- Thick walls stiffened with lignin.
- Made of dead cells, joined with no end walls between them.
What is translocation?
The movement of dissolved sugars from the leaves to the rest of the plant through the phloem.
What is the importance of translocation?
-Moves dissolved sugars made in the leaves during photosynthesis to other parts of the plants, allowing respiration, growth and glucose storage.
What are the key structures in the phloem?
-Cells have end wall with small holes to allow substances to flow through.
What are the factors affecting transpiration?
Temperature, humidity, wind speed, light intensity.
What effect does temperature have on transpiration and why?
Higher temps increase the rate of transpiration because water evaporates faster in higher temps.
What effect does humidity have on transpiration and why?
Lower humidity increases the rate of transpiration because the drier the air, the steeper the concentration gradient of water molecules between the air and leaf.
What effect does wind speed have on transpiration and why?
More wind increases the rate of transpiration because wind removes the water vapour quickly, maintaining a steeper concentration gradient.
What effect does light intensity have on transpiration and why?
Higher light intensity increases the rate of transpiration because the stomata opens wide to allow more carbon dioxide into the leaf for photosynthesis.
