These plates are examples
of the cuticle and stomata of a Douglas-fir needle. The photos
were taken with a scanning electron microscope. Plates 7 &
9 show the waxy cuticle of Douglas-fir needles. Plates 8 &
10 show pairs of specialized epidermal cells, the guard cells,
that surround microscopic pores in all leaves. In plates 8 and
10, the epidermis has been chemically stripped away to reveal
the stoma (plural stomata), the name for the specialized
guard cells and pores. Carbon dioxide (CO2) diffuses into the leaf
or needle through the stomata. Water also diffuses from the plant
to the atmosphere through the stomata. Plants are capable of controlling
water loss by closing the guard cells when drought occurs.
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