Optical Parameters of Leaves of Seven Weed Species

Absorption coefficient (k), infinite reflectance (R i ), and scattering coefficient (s) were tabulated for five wavelengths and analyzed for statistical differences for seven weed species. The wavelengths were: 0.55 μm, 0.65 μm, 0.85 μm, 1.65 μm, and 2.20 μm. The R i of common lambsquarters ( Chenopodium album L.), johnsongrass Sorghum halepense (L.) Pers., and annual sowthistle ( Sonchus oleraceus L.) leaves at the 0.85-μm wavelength were significantly (p = 0.05) higher than for sunflower ( Helianthus annuus L.), ragweed parthenium ( Parthenium hysterophorus L.), or London rocket ( Sisymbrium irio L.). Annual sowthistle had the largest k value, and Palmer amaranth ( Amaranthus palmeri S. Wats.) had the smallest k value at the 0.65-μm chlorophyll absorption wavelength. In general, johnsongrass, ragweed parthenium, or London rocket had the largest s values among the five wavelengths, whereas annual sowthistle and Palmer amaranth were usually lowest.