Orchid petal. Coloured scanning electron micrograph (SEM) of the surface of a petal from a Phalanopsis sp. orchid. Two stomata are seen left and right of centre. These are pores in the petal that can open or close to regulate gaseous exchange and water content within the petal. Phalanopsis orchids are widely used as houseplants for their striking colours and pleasant smell. Magnification: x425 at 6x7cm size.