2. How does photosynthesis differ between 'sun' and 'shade' plants or leaves?


Plants are usually adapted to growth in direct sunlight or shaded conditions. Similar differences are observed among the leaves of large trees; those leaves that develop under the shade of other leaves are anatomically and metabolically different from those that grow on exposed canopy surfaces.

Shade-type leaves typically are thinner, have more surface area, and contain more chlorophyll than those of sun leaves. As a result, shade-leaves (curve B) often are more efficient in harvesting sunlight at low light levels; remember, the slope of the line observed under low light conditions is a measure of photosynthetic efficiency. However, sun-leaves (curve A) display a higher light saturation point and maximum rate of photosynthesis. Why do these differences make sense?


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Copyright (C) 1998, Steven R. Spilatro, spilatrs@marietta.edu. All rights reserved