Spectral reflectance changes in greenhouse-grown metal-doped plants

Abstract

Greenhouse-grown Hosta ventrlcosa plants were doped with copper acetate, copper sulfate, zinc acetate, zinc sulfate, cobalt acetate, or nickel sulfate. The metallic compounds were applied to the plant substrate as aqueous solutions or dry powders. Spectral reflectance of the leaves in the region of the electromagnetic spectrum between 0.4 and 0.8 ym was measured over time. Compared to controls, plants with added copper or zinc sulfate exhibited few spectral changes. The addition of zinc acetate, cobalt, or nickel, however, produced increased reflectance between 0.5 and 0.65 ym, a lower reflectance on the near-infrared plateau, and a shift in the long-wavelength edge of the chlorophyll-absorption band centered near 0.68 ym to a shorter wavelength. The first two spectral differences also occur with changing age and water content of leaves. The shift in the edge of the chlorophyll-absorption band, however, has not yet been observed except when anomalous metallic elements are present.