Pondweed leaf. Light micrograph (LM) of a pondweed leaf (Elodea sp.). The leaf is toothed with leaf hairs, or trichomes, along its edge. A large central vein (dark green) carries nutrients to and from the leaf. Within the cells a few chloroplasts are visible as tiny green dots. Their colour comes from the photosynthetic pigment chlorophyll they contain, which is vital for the production of nutrients from sunlight. Elodea sp. have their leaves arranged in whorls around the stem. They are widespread water plants, which are native to North and South America. Magnification: x20 at 5x7cm size.