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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‐µL 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.

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Intact shoot apex development of the carnation was studied with a scanning electron microscope using fresh tissue. Reproductive meristems were more resistant to desiccation from the hard vacuum and electron beam than vegetative meristems. Vegetative meristems, however, can be studied if the work is done quickly. Structural changes which occurred in the developing carnation shoot showed that leaf primordia are initiated in a circular whorl. Floral initiation was easily determined by the appearance of a flattened apex and a pentagonal whorl of sepal primordia. Subsequent centripetal initiation of flower parts was easily recognized and identified.