The nodal roots of Zea: their development in relation to structural features of the stem

Abstract

The framework of the root system of a mature, field-grown corn plant of variety Seneca Chief consists of about 70 axile roots. One of these is the primary root. The others develop on the stem, a single tier at each of the seven basal nodes. Just over half of these roots grow out at or above ground level from nodes 6 and 7 late in the development of the plant, with those of node 7 entering the soil just before flowering. The mean diameter of the root produced at successively higher nodes increases, as does also the mean number of large metaxylem elements seen in a cross section, so that about 75% of the large xylem conduits between the root system and the stem are in the roots of the two uppermost tiers. Nodal root primordia develop initially in situ from an extensive region of dedifferentiated stem cortex. A sleeve-like extension of the stem encloses the base of each root formed at aerial nodes. At each node the complexity of vascular interconnections results in all of the framework roots being indirectly linked to each other and to the vascular traces from all of the leaves.

Comparative Transcriptome Profiling of Maize Coleoptilar Nodes during Shoot-Borne Root Initiation

“…prior to observable histological differences between the two genotypes), a considerable number of differentially expressed genes were detected. Likely, these genes are associated with the dedifferentiation of cortex cells (Hoppe et al, 1986), an RTCS-dependent process that precedes the first cell divisions in the coleoptilar node. Similar results were obtained in a comparative transcriptome survey of the wild type and the lateral root-deficient mutant rum1 (Woll et al, 2005).…”

“…Similarly, significant differences in global gene expression levels have also been observed in primary roots of different maize inbred lines and hybrids prior to the manifestation of morphological differences between the roots of these genotypes (Hoecker et al, 2008;Paschold et al, 2012). The increasing numbers of differentially expressed genes after the initial cell divisions in the crown root primordia (t2) and shortly before the appearance of the crown roots (t4) correspond to the increasing histological differences in the coleoptilar nodes of the wild type and rtcs that are a result of the cell divisions leading to crown roots in wild-type coleoptilar nodes (Hoppe et al, 1986). A set of 93 genes display RTCS-dependent expression throughout all three stages of early crown root formation in the coleoptilar node.…”

Root Xylem Embolisms and Refilling. Relation to Water Potentials of Soil, Roots, and Leaves, and Osmotic Potentials of Root Xylem Sap1

“…Individual nodal roots of tiers 1 to 4 (terminology of Hoppe et al [1986]) were located within the soil close to the base of the stem by gentle probing with fingers. The soil surrounding an approximately 4-cm-long portion of each root close to its base was removed by hand to minimize disturbance to the root and its short, determinate laterals.…”

Grasses suppress shoot-borne roots to conserve water during drought

“…Later during development, roots borne from the crown initiate and emerge from internal tissues. This important developmental transition represents the beginning of the postembryonic shootborne root system (4, 6, 7), which will come to dominate the architecture of the plant below ground (2,8,9).…”