“Light Gradients in Shoots Subjected to Unilateral Illumination—Implications for Phototropism”, 1984-07-01 ():
When an organ is subject to unilateral illumination, light entering the organ is attenuated very efficiently and the irradiance at the ‘shaded’ surface is only a small percentage of that at the illuminated surface. The light gradient across the organ is ~exponential, being steepest across the first few cell layers. The penetration of light into an organ was found to be similar with red or blue light and was largely independent of the pigmentation of the organ. Studies of light transmission in organs infiltrated with liquids of different refractive index showed that refraction and reflection were the main factors in establishing the light gradient in organs.
The implications of the measured light gradients are discussed briefly in relation to models of phototropism.