Morphological and Anatomical Characterization of Leaf Burn in Corn Induced from Foliar‐Applied Nitrogen¹

Abstract

Abstract Foliar applied nutrients have been used to overcome nutrient deficiencies on a variety of crops; however, leaf burn is often a problem. Corn ( Zea mays L.) Plants were treated with 120 g N L −1 from urea to study the leaf burn phenomenon. A 4‐ µ L drop applied to the adaxial leaf surface was observed at 2‐h intervals for 8 h. Leaf samples were studied with dissecting, compound, and scanning electron microscopes for changes resulting from the application of foliar applied fertilizer salts. Damage observed under the dissecting microscope after 2 h consisted of a darkening in the epidermal cells. After 8 h, 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 h. Disorganization of mesophyll was observed after 8 h. Scanning electron microscope (SEM) micrographs revealed collapsed and wrinkled epidermal cells with sunken stomates after 2 h. Events associated with visual damage appear to be related to water loss since epidermal and mesophyll cells become desiccated.