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A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology - Question 9 - 2018 - Paper 1
Question 9
A student compared the number of stomata on the upper and lower surfaces of a leaf. She completed a leaf peel as shown in Figure 22. The layer of nail varnish shows... show full transcript
Worked Solution & Example Answer:A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology - Question 9 - 2018 - Paper 1
Step 1
Step 2
Explain why the leaf peel rather than the whole leaf was viewed with a microscope.
Answer
The leaf peel is used instead of the whole leaf because it is thin, allowing light to pass through easily. This transparency is crucial for observing the stomata and guard cells effectively under a microscope.
Step 3
Step 4
Describe how stomata open.
Answer
Stomata open when the guard cells take in water. This process occurs by osmosis, where water moves from an area of lower solute concentration to higher solute concentration. As the guard cells swell with water, they become turgid and change shape, causing the stomatal pores to open.
Step 5
Use Figure 24 to help you describe how water and sucrose move through a plant.
Answer
Water moves through the plant primarily via the xylem, which is made up of dead cells that form narrow, hollow tubes. It carries water and mineral ions from the roots to the leaves, driven by the process of transpiration. This movement occurs as water evaporates from the leaves, creating a negative pressure that pulls water upward.
In contrast, sucrose, a sugar produced during photosynthesis, is transported through the phloem. The phloem consists of living cells that have sieve tubes. Sucrose is moved from the leaves to other parts of the plant, including roots and flowers, through a process known as translocation, which can involve active transport.