Initial nodal roots, growing from the first nodes of stem in the crown area tend to grow laterally before turning downwards. Each branch of each lateral nodal root has its own root tip. Nodal roots are formed near to stem vascular system of the stem, even in the crown, allowing efficient transport of minerals and water into the stem, through the xylem and then further to the expanding leaves. Photosynthesis products are moved through the phloem into the vascular system of the roots to allow expansion of the nodal roots.
Temperature influences the metabolism rate in the root tissue and thus affects the growth rate of the nodal roots. Although water movement into the root tissue and movement up the plant is mostly influenced by other physical factors such as outside relative humidity, transport of nutrients such as glucose from leaves to roots in phloem is slower if temperatures are reduced. Auxins influencing the root tip expansion are produced in leaf tips, moved through phloem and therefore are slower to reach root tips if temperatures drop.
Genetics influence the pattern of nodal root growth, some hybrids with more lateral roots than others. It is common for corn hybrids to develop roots from 6 underground and 3 above ground nodes during the life of the corn plant. Genetics and environments influence the actual number. Soil types and depth, organic distribution in soil and water distribution all become factors in determining the most efficient nodal growth pattern appropriate for a field. A change in any of these factors may favor a different set of genetics the next 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.