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Photosynthesis is the process by which green plants trap light energy and use it to make carbohydrates.

When light strikes a leaf:

• some (12 per cent) is reflected
• some (5 per cent) is transmitted through the leaf
• the rest (83 per cent) is absorbed by the pigments within the chloroplasts

Pigments are chemicals found within the chloroplasts which absorb light energy and convert it to chemical energy. The principal pigments are chlorophyll a and b - they mainly absorb light in the red and blue wavelengths of light.

Plants also contain carotenoids (carotene and xanthophyll) which absorb light from other regions of the spectrum, extending the range of wavelengths absorbed and pass the energy on to chlorophyll for photosynthesis.

Investigating photosynthesis pigments

The different photosynthesis pigments in leaves can be investigated using thin layer chromatography. Watch this video to see the correct procedure for carrying out this practical.