How photosynthetic function is reflected in cellular structures
In this transverse slice through a pine needle you can see at least three cell types. Leaves/needles are the major site of photosynthesis in plants. At the outer edge there is a layer of tall, narrow cells closely packed in a single, tight row. These are palisade mesophyll cells that collect the light for photosynthesis and contain lots of chlorophyll. The next type of cells are irregularly shaped cells with more spaces between them called spongy mesophyll. The spaces allow for photosynthetic gas exchange. Last, you can see a circle of round cells that are not green. This is a resin duct. Pine needles contain several resin ducts that transport resin throughout the needle.