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a) The diagram shows a celery stem in some red dye - Edexcel - GCSE Biology - Question 4 - 2017 - Paper 1
Question 4
a) The diagram shows a celery stem in some red dye. The red dye moves up the celery stem. A student used five sets of this apparatus to study the rate of transpirat... show full transcript
Worked Solution & Example Answer:a) The diagram shows a celery stem in some red dye - Edexcel - GCSE Biology - Question 4 - 2017 - Paper 1
Step 1
Suggest how these five sets of apparatus could be used to measure the effect of light intensity on the rate of transpiration.
Answer
To investigate the effect of light intensity on transpiration, the student can set up five different arrangements of the apparatus with varying distances of a light source. Each arrangement will allow the red dye to move through the celery stem under different light intensities. The student should ensure that all other factors, such as temperature and humidity, are kept constant to ensure a fair test.
Step 2
Explain why the rate of transpiration decreases between 25°C and 30°C.
Answer
At higher temperatures, specifically between 25°C and 30°C, the rate of transpiration decreases potentially because the plant starts to lose water more rapidly than it can absorb from the soil. This can occur due to the closing of stomata to prevent excessive water loss, leading to decreased transpiration rates.
Step 3
Complete the sentence by putting a cross (X) in the box next to your answer.
Answer
The percentage increase in the rate of transpiration between 10°C and 15°C is 100%. This is calculated as follows:
Increase in transpiration = 8 - 4 = 4 arbitrary units. Percentage increase = ( rac{4}{4} \times 100 = 100%)
Step 4
Explain one way in which root hair cells absorb mineral ions from the soil.
Answer
Root hair cells absorb mineral ions through active transport. This process requires energy, allowing the cells to take in ions from a lower concentration in the soil to a higher concentration inside the cells, effectively enhancing nutrient uptake.
Step 5
Explain how water moves from root hair cells, across the root and into the stem.
Answer
Water moves from root hair cells via osmosis, moving along a concentration gradient through the root cortex to the central cylinder (stele). Once in the stele, water travels through the xylem vessels to reach the stem and the rest of the plant.