Water-lily leaf stem. Light micrograph of a cross- section through the leaf stem (petiole) of a white water-lily (Nymphaea alba). This shows the air canals (empty spaces, blue) in the tissue, which make the water-lily buoyant. This type of air- filled tissue is known as aerenchyma, and also improves respiration and photosynthesis. The air spaces are lined by thick wall cells, called sclereids, that have an irregular shape.
Model release not required. Property release not required.