Plant Responese to the Light Penetrating Snow

The spectral irradiance of light penetrating 198 cm of snow was measured with a device employing a photomultiplier tube combined with each of several interference filters. In deep snow, the measured peak in transmission was near 500 nm, but in older, shallower snow the peak shifted to 550 nm. On 2 dates, measurement were made periodically under snow before and after sunrise. There was a spectral shift toward the longer wavelengths with increasing height of the sun above the horizon. Germination of Lactuca sativa cv. Grand Rapids seeds was promoted by a 3—h exposure to the light penetrating 198 cm of snow, and Brassica nigra and Brassica kaber seeds responded similarly to longer exposures under deep snow. Leaf greening, leaf unfolding, and inhibition of shoot elongation were exhibited by Camassia quamash in response to light penetrating the snow, but phototropism was not observed in an experiment designed to detect it.