One protection from excessive water loss in corn is a waxy layer deposited on the outside of the leaf and stem epidermis cells. This cuticle is composed of waxy polymers that are hydrophobic. Leaves younger plants up to V4 stage tend to have more crystalline forms but older leaves form smother, more flat, smooth formats. Cuticular waxes are manufactured in the cytoplasm of the epidermal cells as a solute in solvents such as alcohols, ethers and fatty acids. The solution move through the cell walls to the surface, allowing the solvent to evaporate and deposit the wax layers.
At least 18 genes, referred to glossy genes have been identified affecting cuticle formation and composition of corn leaves. Various combinations of these genes influence the thickness of wax as well as the nature of the cuticle. Most corn varieties have a crystalline form in the younger leaves although some gene mutations will extend crystalline type of wax beyond these development stages. The change from crystalline wax to the smoother wax apparently is related to the tendency for herbicides (plus surfactants) to be absorbed more in mature leaves than in immature leaves.
Cuticle waxes provide several important functions to the corn plant. Loss of water via evaporation through epidermal cells is greatly reduced. Waxes become the initial barrier for potential pathogens both because of becoming a structure for the pathogen must overcome but also, being hydrophobic, encouraging water runoff. Only a few fungi and bacteria species can manage to overcome this protection. Cuticle waxes also offer protection against UV radiation with its potential mutagenic effects.
Corn plants respond to dry atmosphere by producing more wax on leaf surfaces. Leaves of corn grown in the drier air of Nebraska develop a thicker waxy surface than the same hybrid grown in Ohio.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.