Monocot RootMonocot Root
Roots anchor the plant, absorb minerals and water, conduct water and nutrients, and store food. Monocots, including grasses, generally have fibrous root system consisting of a mat of threadlike roots that spread out below the soil surface. A single rye grass plant, in a growing season of only four months, produces about 600 km of roots. The fibrous root system not only gives the plant expansive exposure to soil water and minerals, but also anchors the plant tenaciously to the earth.
Most absorbtion of water and minerals occurs near the root tips, where vast numbers of tiny root hairs increase the surface area of the root tremendously. In addition to roots that extend from the base of the shoot, some plants have roots arising above ground from stems or even from leaves. Such roots are said to be adventitious. These roots function as props that help support the stems. An example of this is corn.
The protoderm, the outermost primary meristem, gives rise to the epidermis, a single layer of cells covering the root. Water and minerals that enter the plant from the soil must cross the epidermis. The root hairs enhance this process by greatly increasing the surface area of epidermal cells. The procambium forms a central vascular cylinder called the stele. This is where the xylem and phloem develop. The stele of a monocot generally has a central core of parenchyma cells, often called the pith, which is ringed by vascular tissue with the same alternating pattern of xylem and phloem as in dicots. The ground tissue fills the cortex, the region of the root between the stele and the epidermis. The innermost layer of the cortex is called the endodermis. This forms the boudary between the cortex and stele.The endodermis functions as a selective barrier that regulates the passage of substances from the soil solution into the vascular tissue of the stele.
An established root may sprout lateral roots, called secondary roots, which arise from the outermost layer of the stele. Just inside the endodermis is the pericycle, a layer of cells that may become meristematic and begin dividing again.