THE EFFECT OF LEAF HAIRS OF VERBASCUM THAPSUS ON LEAF ENERGY EXCHANGE

Abstract

Energy budgets were determined for normal and hairless leaves of Verbascum thapsus L. in a wind tunnel. Leaves with the dense hair present were warmer than hairless leaves. This was shown to be due to a thicker boundary layer over normal leaves. Boundary layer resistance to heat and water vapour loss was higher for normal than for hairless leaves, resulting in lower convection and transpiration from normal hair‐covered leaves. Differences in transpiration resistance were correctly predicted by heat transfer theory. The hairs had little effect on radiation absorption by the leaves. Copyright © 1970, Wiley Blackwell. All rights reserved