Plant Structure and Transport in Plants — O/L Science

How do I practise Plant Structure and Transport in Plants?

1 question with a worked solution · 5 marks

1. 2018 · Paper II · 5 marks
   Question 3 works from a leaf seen in cross-section under a microscope. It asks you to name the layer holding the most chloroplasts and say why, to state what the stomata do and describe how they open and close, and to explain why a variegated leaf makes starch only in its green parts.
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   (i) The palisade mesophyll layer contains the most chloroplasts — it is near the upper surface and receives the most light for photosynthesis. (ii) Stomata allow gas exchange (CO₂ in, O₂ out) and transpiration. Guard cells swell (fill with water) in light → pore opens; lose water in dark/dry → pore closes. (iii) White regions lack chlorophyll (no chloroplasts) → photosynthesis cannot occur → no starch produced. Only green regions with chloroplasts carry out photosynthesis.
   Source: Department of Examinations, Sri Lanka — G.C.E. O/L Science 2018, Paper II, Question 3 · https://doenets.lk/pastpapers

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