Comparison of Adaxial and Abaxial Surface Reflectance Under Different Nitrogen Level

A field experiment was conducted in 1999 to investigate differences of adaxial and abaxial surface reflectance of rice leaves under 5 levels of nitrogen fertilization. Reflectances from the abaxial surfaces were greater than that from the adaxial surfaces in the visible and near infrared region at tillering, booting and flowering stage. The absolute difference (mostly below 2%) between the two surfaces was not considerably influenced by nitrogen availability and growth stage in the visible region, but the magnitude of differences in the near infrared region decreased with the growth stage. Reflectance data from the abaxial surfaces were related to leaf chlorophyll and nitrogen concentrations as strongly as that from the adaxial surfaces, but the data from the adaxial surfaces were more sensitive in response to variation in leaf chlorophyll or N concentrations. The greater reflectance from the abaxial surface may be attributed to the convex shape and the more intensely arranged epidermis cells on the surface.