Light Filtration by Foliar Canopies: Significance for Light-Controlled Weed Seed Germination

Abstract

Light from sunlight, incandescent, and fluorescent sources was filtered through fresh tobacco ( Nicotiana tabaccum L.), corn ( Zea mays L.), and soybean ( Glycine max (L.) Merrill) leaves. The spectral quality of the leaf-filtered light showed that much more of the incident red energy was absorbed than the far-red. The effect of the leaf-filtered light on the phytochrome-controlled germination of six weed species was generally to inhibit germination of seeds given a stimulatory pre-irradiation of red light from a standard source. Germination of seeds with no pre-irradiation was either not promoted or promoted to various degrees. Unfiltered light, at intensities equivalent to those under the leaf filters, caused no comparable effects. These results indicate an effect of altered spectral quality of the leaf-filtered light on the ratio of inactive/active phytochrome (P r /P fr ) in the underlying seeds. We suggest that such phenomena could influence the germination of weed seeds in the field.