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Figure 1 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake - Edexcel - GCSE Biology Combined Science - Question 1 - 2020 - Paper 1
Question 1
Figure 1 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake. (a) Water lilies have stomata on the upper surface of the leaves. Explain w... show full transcript
Worked Solution & Example Answer:Figure 1 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake - Edexcel - GCSE Biology Combined Science - Question 1 - 2020 - Paper 1
Step 1
Explain why water lilies have no stomata on the lower surface of the leaves.
Answer
Water lilies have no stomata on the lower surface of their leaves primarily because:
- Gas Exchange: The lower surface of the leaf is submerged in water, which means it is not in contact with air. Consequently, gas exchange (specifically the uptake of carbon dioxide and the release of oxygen) cannot occur effectively.
- Water Entry: The stomata are located on the upper surface to allow the entry of water vapour and gases when conditions permit. This adaptation helps to limit the water loss from transpiration.
Step 2
Step 4
Describe how this sugar is transported from the leaves to the flowers of the water lily.
Answer
The sugar (sucrose) is transported from the leaves to the flowers of the water lily through the following mechanisms:
- In the Phloem: Sucrose is transported in the phloem, which is the vascular tissue responsible for the transport of nutrients.
- Dissolved in Water: It is dissolved in water, allowing it to move easily within the plant's vascular system.
- Translocation: The process of translocation enables the movement of sucrose from areas of high concentration (leaves) to areas of lower concentration (flowers), ensuring efficient delivery to growing tissues.
- Active Transport: Some movement may involve active transport mechanisms to facilitate the uptake of sucrose into the flower cells against a concentration gradient.
Step 5
Explain why this non-indigenous plant now covers the whole surface of the lake.
Answer
The non-indigenous water lily plant has spread to cover the entire surface of the lake due to several factors:
- Favorable Conditions: The conditions in the lake, such as light, temperature, and water quality, are suitable for its growth and photosynthesis.
- Competitive Advantage: It may have outcompeted native plants for resources like light and nutrients, allowing it to thrive.
- Reproduction: The plant likely reproduces rapidly, contributing to its increased coverage.
- Lack of Natural Herbivores: Additionally, the absence of natural herbivores that would typically control its population can allow it to proliferate unrestricted.