A Morphological And Anatomical Characterization Of Leaf Burn Induced From Foliar Applied Nutrients

Abstract

Foliar applied nutrients have been used to overcome nutrient deficiencies on a variety of crops; however, leaf burn is often a problem. Zea mays plants were treated with 12% N from urea to study the leaf burn phenomenon. A 4 μl drop applied to the adaxial leaf surface was observed at 2 hr. intervals for 8 hrs. Samples were studied with a dissecting, compound, and scanning electron microscope for changes resulting from the application of foliar applied fertilizer salts. Damage, observed under the dissecting microscope after 2 hrs., consisted of a darkening in the epidermal cells. After 8 hrs., the epidermis was desiccated, sunken, and discolored forming a lesion on the leaf surface. Slides of leaf sections showed wrinkling and collapse of epidermal cells at 4, 6, and 8 hrs. Disorganization of mesophyll was observed after 8 hrs. SEM micrographs revealed collapsed and wrinkled epidermal cells with sunken stomates after 2 hrs. Events associated with visual damage appear to be related to water loss since epidermal and mesophyll cells become desiccated.