The transmission of light and total radiation by leaves

Abstract

Diffuse light transmitted through leaves was measured by photoelectric methods for total and colour transmission. Tropaeolum major and Syringa vulgaris leaves transmitted 38% of the energy from mixed sunlight and skylight; Tropaeolum transmitted 56-68% in the near infra-red, 35-44% in the visible region beyond 700 m/*, 7-13% of the entire red, 4-10% of the green, less than 0.5% of the blue. The darker Syringa leaves, with the same total transmission, transmitted about half as much in the short-wave region. The results explain the large percentage of red in forest light; but the relatively greater sensitivity of the eye to green causes the leaf to appear green when held up to the light.