Morphology and Chlorophyll Content of Shade and Sun Leaves of Two Legumes1

The increase in the ratio of leaf area to leaf weight which occurs with shading of legumes was associated with changes in leaf morphology and chlorophyll content. Alfalfa and birdsfoot trefoil had more stomata per cm2 of leaf when grown in the sun than in the shade. Sun leaves of both species were thicker than shade leaves. Number of palisade and mesophyll cells and cell volume appeared greatest in sun leaves, and the palisade layer was more clearly differentiated. Shaded leaves contained more chlorophyll per unit of leaf weight but less per unit of leaf area than sun leaves.