The importance of anatomical structure of roots for physiological processes

Besides the characteristics of the species, the inner structure of the root is influenced by the place and time of origin during the growth period. From the root tip up to the base of a particular root the zones of cell division, cell elongation, formation of root hairs and those zones of the root branching by different aging processes can be distinguished. The root tip which is covered by a root cap and mucilage is protected against evaporation and water contact. From the end of the root cap the cells are exposed. The cells can elongate by water uptake or shrink by water loss. All processes of geotropic growth take place there. Some differences are illustrated using the example of Zea mays plants. Seedling roots, roots emerging from several nodes of the shoot as well as lateral roots of different orders will be compared. The distances from the tip and from the base of the root are also very important. Distinctive features as root diameter, the size of the stele and of the cortex, the relation of cortex and stele, the number and width of the xylem vessels, the size of cells, special thickenings, stage of lignification as well as symptoms of maturation are observed.