DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Pine needle. Light micrograph of a transverse section through a leaf (needle) of a pine tree (Pinus sp.). The leaves are needle-like so they present a large surface area for photosynthesis but prevent too much water loss (transpiration). The epidermis (red, top) is made up of thick walled cells covered with a thick layer of cuticle. The mesophyll (pink) under the epidermis is made up of parenchyma cells with in-folded walls to increase the area of chloroplasts for photosynthesis. Magnification: x230 when printed 10 centimetres wide.
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