Photosynthesis and Plant Nutrition

Practice past-paper questions

Practise O/L exam questions on Photosynthesis and Plant Nutrition with worked solutions

1. 2023 · Paper II · 6 marks
   A student placed a green leaf in the dark for 48 hours (destarched). It was then illuminated for 6 hours. The leaf was tested for starch using iodine solution. (i) What result would you expect and why? (ii) Write the word equation for photosynthesis. (iii) Name TWO factors that limit the rate of photosynthesis in a plant kept indoors.
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   (i) The iodine solution turns BLUE-BLACK where starch is present — expected in the illuminated leaf because the plant performed photosynthesis during the 6 hours of light, producing and storing starch. (ii) Carbon dioxide + Water → (light energy) → Glucose + Oxygen (iii) Low light intensity; low carbon dioxide concentration (temperature could also be limiting if indoor temp is low).
   Source: NIE O/L Science 2023 Paper II Q4

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