Corn stalk cells of the rind have thick walls with lignin, hemicellulose and cellulose, all carbon-based compounds formed after carbohydrates were shipped to the stem locations. Rind cells are major barriers to pathogens and insects and contribute to the withstanding of lodging pressures. Hybrids vary in the thickness of the rind with strength measured with special penetration equipment.
Stalk pith tissue is composed of parenchyma cells with thinner walls allowing import of sugar molecules. Cytoplasmic activity in these cell plasmids converts the glucose into starch molecules. This functions as an energy storage for future use in roots and grain, as hormones directs the movement. As grain begins to form, sugars are moved at a steady daily pace. When stresses, such as leaf disease, or hail damage to leaves or cloudy weather reduce photosynthesis, the reserve from the stalk cells is pulled to the grain.
Vascular tissue in the stalk becomes the vehicle for the movement to the grain and root, while the xylem supplies moisture to the stalk cells from the root.
Stalk pith cells connect to the rind cells, essentially a solid rod of the stalk and thereby adding to the stalk total strength. Some have estimated that this is about 33% of the total stalk strength.
Movement of sugars to the grain can result in deprivation of sugar needs for root tissue, resulting in early death of root tissue. This reduces the uptake of water by roots eventually causing the leaves to wilt and the stalk parenchyma cells to collapse. The latter results in pith cells to pull away from the rind, essentially changing the rod structure to a tube. Death of these cells allows the advance of fungi as active cell metabolic resistance is no longer effective. Consequently, the stalk easily lodges. We often refer to these as stalk rot as fungi present are identified. The real problem, however, was the starving of roots.
Photosynthetic stresses combined with the draw of sugars to the grain reduced the available of chemical energy for root cells. Death of the root resulted in wilting of plant and redaction of stalk pith cells. Withdrawal of the pith cells away from the rind cells weakened the strength of the stalk.
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.