Tissues and Organs - The leaf


The leaf is primarily an organ for photosynthesis. It is also well adapted for gas exchange and many leaves are highly adapted to reduce water loss by transpiration.

The leaf has a large surface area which maximises the absorption of light for photosynthesis. It is thin, and so photosynthesising cells are not far from the leaf surfaces where light absorption and gaseous exchange occur.

  • Upper epidermis - the upper protective layer of the leaf and lack chloroplasts so is not directly involved in photosynthesis. It is covered with a waxy cuticle to provide waterproofing and reduce water loss.
  • Palisade mesophyll - the primary photosynthesising region in the leaf consists of tightly packed cells and occurs immediately beneath the upper epidermis (to maximise harvesting of light energy). It is adapted for maximal light absorption. Each cell has many chloroplasts to maximise photosynthesis
  • Spongy mesophyll - lies immediately beneath the palisade layer. The cells are much more loosely and irregularly arranged, this arrangement…


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