Leaf Angle: An Adaptive Feature of Sun and Shade Leaves

Ten woody deciduous dicot species, ranging from obligate sun plants to facultative sun/shade plants, were grown in full sun and approximately 17% of full sun. Observations of leaf orientation showed that the leaves of most species are slanted, some to nearly vertical, in full sun and are more nearly horizontal in the shade. Although no preferential orientation for compass direction was observed, these responses may be useful. The sun position should enhance photosynthetic capacity and efficiency and promote leaf cooling during high solar radiation. The shade position should maximize the individual leaf photosynthetic input.