Most of the carbohydrates in a corn plant are found in cellulose and related polysaccharides such as pectin and lignin as cell wall components. There are multiple genes involved in the synthesis of these compounds that are composed linking glucose molecules together as cells complete the expansion stage of plant growth. Individual tissues differ in the amount and thickness of the cell walls. Leaf epidermal cells have thicker cell walls than the parenchyma cells within the leaves. The complex components and toughness of the leaf epidermal cell wall allows an initial defense against micro-organisms and insects. Lignin components of these outer cells are especially important because of the difficulty of digestion by insects such as the corn borer (Ostrinia nubilalis).
Parenchyma cells within the leaves have thinner cell walls allowing these living cells to function as main sites of photosynthesis in the leaves and as storage units in the corn stalk. Cells surrounding the phloem and xylem cells of the vascular bundles become thicker as the leaves expand. Much of that comes as the lignin component increases. Xylem cell walls thicken with more lignin as well.
Corn stalks increase in strength as cells forming the outer rind increase in lignin components. Most of the lignification in stalk rind occurs after completion of internode elongation. Lignification strengthens the stalk making it less vulnerable to insect invasion and lodging. The process is not always uniform, being influenced by environment factors such as temperature, water and minerals. Hybrids differ in vulnerability to ‘brittle snap’ in which the plants a few weeks before flowering can break at a node during wind storms. Some aspect of lignification of is related to this problem.
Mature plant stalk strength is related to the combination of cell wall strength of the outer stalk cells and the attachment of the inner parenchyma cells to those rind cells. These form the mechanical strength of a rod versus that of a tube if desiccation of the parenchyma occurs if the plant wilts because of root rot later in the season.
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.