Scanning electron micrograph (coloured green) of the upper surface of a pea leaf, Pisum sativum, with the epidermis (left) stripped off (right) to show the palisade mesophyll layer beneath. The waxy epidermis is studded with open stomata, tiny pores that regulate gaseous exchange between the plant & the atmosphere. The palisade cells are elongated & packed closely together. They contain the chloroplasts, cellular organelles involved in the manufacture of starch from the sun's energy, carbon dioxide & water (photosynthesis). During daylight when photosynthetic activity is high the stoma are open,at night or during a water shortage the pores close. Mag: X 100 (35mm). Original Original is B/W print B 745/46M