In pine trees photosynthesis takes place in the pines, where the chlorophyll is concentrated. As the tree ages it loses foliage and relies more on concentrated stores of energy. For both of these reasons photosynthesis gradually declines as each tree ages. In contrast, the life-cycle of most grasses, which are either annuals or short-lived perennials, is much shorter and accordingly they have high concentrations of chlorophyll to facilitate high energy capture and rapid growth.
