Monocot and Eudicot/Dicot Roots
Roots (below ground) The first structure to appear when a seed germinates and is called the radicle in the embryo. The function of the root system is to absorb water and nutrients from the soil for the growing plant, as well as providing a stable anchor.
Water is absorbed by a process called OSMOSIS (Note: Root cells are usually hypertonic to soil, so water will enter the cells passively by osmosis.) The walls of root cells are very thin and have a large surface area. The depth of the root depends on the moisture content of the soil.
Two main types of roots:
Taproots are long and thick and have secondary roots emerging from that root. Dicots have taproots. Fibrous roots are many roots of about the same size, each with secondary roots. Monocots have fibrous roots.
Another type of root called the Adventitious roots are when the roots emerge from other tissues like the stem and leaves, and prop up the plant in support. Tuberous roots are a lateral root that is specialized to store carbohydrates. Example: yams, cassava
General Structure Each root has a meristemic area near its tip to allow for growth. Meristem - where cell division takes place (growth) - where new cells are made At the tip of each root is a cluster of cells forming the root cap; these cells produce a mucus-like substance which lubricates the movement of the root through the soil. Root hairs increase surface area of the epidermis increasing absorption of nutrients and water.
Some definitions: copy definitions you need
Xylem – a series of pipes running through the roots, stems and leaves carrying water through plant Phloem – carries food and dissolved materials through plant Vascular Cylinder – central portion of a root that contains the xylem and phloem
Monocot Roots fibrous roots (many branched roots of equal size)
Examples: grasses, grains, corn Cross Section - separate strands of xylem and phloem alternate around a pith-like region
Monocot root epidermis Vascular Cylinder cortex phloem xylem
pith/parenchyma endodermis (Casparian strip)
Note the xylem and phloem in these differently stained monocot roots.
Eudicot Roots tap roots (1 large main root and smaller lateral roots)
Examples: carrots, beets, beans, dandelions, most trees Cross Section xylem is irregular and a solid strand phloem is arranged in separate strands
Eudicot root Vascular Cylinder epidermis cortex phloem xylem
NO pith/parenchyma endodermis
Note the xylem and phloem in these differently stained dicot roots.
More Definitions: Epidermis - provides protection and regulates water movement - epidermal cells can elongate and form root hairs which increase the surface area for water absorption
Cortex - the innermost layer of cortex cells is called the endodermis
- the endodermal cells are coated with a waxy layer called the casparian strip (this prevents water from moving in the spaces between the endodermal cells)
Home Fun: Pg. 516 #3-5 Pg. 518 # 1,4,5,6
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