Prior to pollination corn plants are dependent upon roots to absorb minerals and water to be transferred to the developing above-ground growth. Size and efficiency of roots of each plant are major in supporting the growth. Genetics and environments are major factors in successful leaf and stalk development. Photosynthates produced in the leaves are transported to the roots through living phloem cells to supply energy for growth of the roots and active uptake of minerals. Living cells of root cells, including the root hairs that are active, uptake of mineral ions requires the energy to move them from a lower concentration in the soil to a higher concentration in the root cells.
Water uptake from the soil is moved to the xylem cells, that are essentially non-living tubes, in which the water tension character allows water to be pulled into the root and up to the stem and leaves. As a molecule of water either transpires through leaf stomata or used in new upper cell development, a molecule of water is pulled into the root. Water absorption and transport to above plant parts is a physical process mostly carried out in dead cell tissue but is dependent upon continuation of the tubes.
Mineral transport into roots, and transport of energy for this process, is directed by plant hormones produced in meristems. After pollination, the hormones produced in the seed embryos, direct sugar transport to the developing kernels. As this redirection increases with growth of kernels, transport of energy to the root cells decreases. Water transport system continues but mineral absorption from the soil is reduced. Root expansion stops. One of the functions of the living cells is to ward off potential fungal invaders by actively producing anti-fungal chemicals. As the energy for these cells is reduced, the resistance to microbes also is reduced, increasing vulnerability of xylem being plugged by fungal mycelium.
Now it becomes a race to the finish. Did the plant produce and transport sufficient carbohydrate to root cells before pollination to sustain enough living functions in roots to avoid destruction by fungi?
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.