What is the advantage of having a higher density of stomata on the bottom side of the leaf for most plants? (3 marks)
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What is the advantage of having a higher density of stomata on the bottom side of the leaf for most plants? (3 marks)
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→ Stomata are the pores that appear on the leaf and are responsible for transpiration, i.e. the diffusion of water vapour out of the cell.
→ By having stomata on the underside of the leaf, water won’t be caught on top of the leaf when transpiration occurs.
→ Having stomata pointing down also increases the effectiveness of transpiration by the assistance of gravity.
→ Stomata are the pores that appear on the leaf and are responsible for transpiration, i.e. the diffusion of water vapour out of the cell.
→ By having stomata on the underside of the leaf, water won’t be caught on top of the leaf when transpiration occurs.
→ Having stomata pointing down also increases the effectiveness of transpiration by the assistance of gravity.
The current theory to explain the movement of materials within the phloem of a living plant involves the following steps:
Which of the following is the correct order of these steps?
\(D\)
By Elimination
→ Sugars are created in photosynthetic cells but are required in all cells. Phloem are the series of cells which allow the transport of sugars in plants, and therefore the steps must start with 3 and end with 2 (Eliminate B and C).
→ The current theory states that the movement of materials is driven by osmotic pressure, and therefore osmosis must occur before materials are able to move (Eliminate A).
\(=>D\)
What is the most suitable title for this diagram?
\(B\)
By Elimination
→ The structure shown is one cell thick, and therefore must be phloem, not xylem (Eliminate A and D).
→ The section shown is a longitudinal, not transverse, as a transverse section would show only one cell as it would be viewed from the top or bottom (Eliminate C).
\(\Rightarrow B\)
Ringbarking is the removal of a thin strip of bark from the entire circumference of a tree.
The tree will initially survive, but the roots will eventually die because ringbarking stops
\(D\)
→ Ringbarking removes a large portion, or even all, of the living part of the tree. This will eventually kill the roots as the transport of sugar from the leaves to the roots will be disrupted or ceased completely.
\(\Rightarrow D\)
The diagram shows a vascular bundle from a flowering plant.
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a.
b. → Leaves wilt when they lose water.
→ As xylem tissue is responsible for water transport from roots to leaves, plants with the mutation will wilt easier as the xylem vessels are more likely to collapse with thinner walls.
a.
b. → Leaves wilt when they lose water.
→ As xylem tissue is responsible for water transport from roots to leaves, plants with the mutation will wilt easier as the xylem vessels are more likely to collapse with thinner walls.
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a.
b. → Sugars produced in the leaves are transported into the phloem by active transport.
→ Water from the xylem then follows into the phloem by osmosis, which increases the pressure.
→ This creates a pressure gradient in the phloem allowing the sugar to move up or down the plant.
→ At the ‘sink’, sugars are then removed via active transport to required locations.
b. Transport of sugars through a plant
→ Sugars produced in the leaves are transported into the phloem by active transport.
→ Water from the xylem then follows by osmosis, which increases the pressure in the phloem.
→ This creates a pressure gradient in the phloem allowing the sugar to move up or down the plant.
→ At the sink, sugars are removed actively.