EPICUTICULAR WAX ON JOHNSONGRASS (SORGHUM-HALEPENSE) LEAVES

Studies were conducted to investigate the uniformity of epicuticular wax deposition on leaf blades of johnsongrass. Johnsongrass leaves grown under drought stress had greatly increased epicuticular wax weights compared to leaves from plants with adequate moisture, but relative humidity (95% vs. 40 +/- 5%) had little effect on wax deposition. Wax weights decreased as leaves matured. Sections of lower leaf surfaces of young johnsongrass leaves tended to have more wax than sections of upper leaf surfaces, but weights were nearly equal on upper vs. lower leaf surfaces of older leaves. The narrow side of asymmetrical johnsongrass leaf blades often had more wax per unit area than the wide side. 'rhe area over the midvein contained more wax per unit area than either the narrow or wide side of the leaf blade. Greatest wax concentrations on individual leaves were over the midvein area near the leaf apex. Leaf blades of johnsongrass had more wax per unit area than leaves of corn or grain sorghum.