The ‘transpiration stream’ has an important role in the transport of water and minerals up, into and out of plant leaves - Leaving Cert Biology - Question c - 2021
Question c
The ‘transpiration stream’ has an important role in the transport of water and minerals up, into and out of plant leaves. The water and minerals move through special... show full transcript
Worked Solution & Example Answer:The ‘transpiration stream’ has an important role in the transport of water and minerals up, into and out of plant leaves - Leaving Cert Biology - Question c - 2021
Step 1
Which of the three plants would you expect to show the lowest rate of transpiration? Explain your answer.
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Answer
I would expect Plant B to show the lowest rate of transpiration. This expectation is based on the stomatal density, which indicates the number of stomata per unit area on the leaves. Plant B has the lowest number of stomata (28 per mm²) compared to the other plants, which suggests that it has a reduced ability to lose water through transpiration.
Step 2
Indicate two other ways plants use to control transpiration.
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Answer
Waxy cuticle on the leaves helps to reduce water loss by creating a barrier.
Stomata can open and close in response to environmental conditions, thus regulating gas exchange and transpiration rates.
Step 3
Give two structural differences between xylem and phloem.
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Answer
Xylem contains pits and phloem does not.
Phloem has companion cells and xylem does not.
Step 4
Draw and label a longitudinal section (L.S.) of a xylem vessel.
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Answer
In the diagram, a xylem vessel consists of continuous tubes that are lignified for strength. The vessel has pits that allow water movement between adjacent vessels and a wall composed of lignin.
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