Corn stalk structure is completed by the time of pollination. Leaves are attached at each node, vascular system established to move water and nutrients from the roots to leaves and stalk tissue and to move photosynthesis products, outer cells forming a strong rind tissue to keep the plant upright and pith tissue cells provide a temporary carbohydrate storage tissue.
The most outer epidermis cells of the stalk are green with chloroplasts, although the surrounding leaf sheaths probably limit light penetration. Several rows of cells in from that epidermis form thick walls composed of complex cellulose compounds providing a hard surface to the stalk, especially between the nodes. These cells being difficult to penetrate by pathogens plus the chemical resistance in the living outer epidermal cells inhibit most pathogens from entering the intermodal stalk. The nodal plate, however, is both more vulnerable to fungal penetration and breakage at midseason.
Pith tissue is composed of many, scattered vascular strands composed surrounded by thick-walled cells. Phloem cells within the vascular bundles are living and require carbs to provide energy but the xylem cells are mostly empty tubes. Remainder of pith tissue is composed of relatively large living cells that function to temporarily store carbohydrates that continue to be produced after all leaves are formed. This reservoir becomes especially important as the grain begins to form after pollination and especially when the grain fill rate of about 2% per day occurs 10 days after pollination. This storage allows the plant to provide sugar to the grain even when photosynthesis is reduced on cloudy days or leaf destruction by disease or insects.
Pith tissue also contributes to the strength of the stalk because it is attached to the rind tissue. This essentially makes the stalk a rod and not a tube. This becomes an important aspect of stalk lodging later in the season. After pollination, the corn stalk functions to support the leaves and developing ear as well as a carbohydrate storage unit allowing a steady daily flow to the developing grain.
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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.