Warmup 10/26/15 Tell me a story about roots Objective Tonight’s Homework To learn how the roots of plants function pp 310: 1, 2, 3, 4

Notes on Roots If leaves are for chlorophyll, then what are roots for?

Notes on Roots If leaves are for chlorophyll, then what are roots for? Roots serve 4 purposes: - To anchor the plant (not necessarily in soil) - To absorb water and dissolved minerals - Transport absorbed substances where needed - Store food and starches

Notes on Roots Types of Roots There are exceptions, but generally roots come in two basic types:

Notes on Roots Types of Roots There are exceptions, but generally roots come in two basic types: - A taproot system: These plants have one large root. Secondary roots may or may not grow out of it, but the main root is always biggest.

Notes on Roots - A fibrous system: In these plants there is no main root. As the plant grows, it sends more roots out from the base or lengthens the existing roots.

Notes on Roots As a general rule, roots grow out instead of down. A 4-month-old corn plant may have more than 150 meters of roots, barely extending farther than 5 feet down.

Notes on Roots Root Growth Roots have 4 regions that dictate their growth.

Notes on Roots Root Growth Roots have 4 regions that dictate their growth. - The root cap is a thick mass of dead cells. These protect the root as it pushes through hard soil.

Notes on Roots - The meristematic region is the part going through new growth. These cells are rapidly dividing. This is the part of the root that is actually new.

Notes on Roots - The meristematic region is the part going through new growth. These cells are rapidly dividing. This is the part of the root that is actually new. - The elongation region is where the root becomes longer. The cells here are still fairly new and are filling with water, stretching out longer as they go. This pushes the root cap down more.

Notes on Roots - The maturation region is where the cells are finally stable. These cells are able to change and grow into other structures as needed. Small hairs grow from this section. These hairs, called “root hairs” help to grab nutrients the plant would not be able to reach otherwise.

Notes on Roots Root Tissues - Epidermis The one-cell-thick layer that forms the skin of the root.

Notes on Roots Root Tissues - Cortex This is a thick layer that usually stores nutrients for the plant.

Notes on Roots Root Tissues - Endodermis The endodermis is also one layer thick and acts as a barrier, preventing any nutrients from getting through unless they pass through these cells.

Notes on Roots Root Tissues - Pericycle This layer is a vascular tissue that helps with growth. When secondary roots appear, they grow out from this tissue.

Notes on Roots Root Tissues - Pith This is the inner core of the root and is used for water storage, support, and used to be old tissue.

Notes on Roots Secondary Growth At a point, the root can no longer grow any thicker. When a plant reaches this point, it starts to grow new xylem and phloem on the outer edge. This leaves part of the plant exposed. To protect itself, the plant grows cork cells to protect the soft tissue. This gives the root a new outer layer and the root can continue to grow both longer and thicker.

Exit Question What is the difference between a taproot and fibrous root? a) Taproots have reached max growth, fibrous haven’t b) Fibrous roots have reached max growth, taproots haven’t c) A taproot is one main root, fibrous roots have many d) A fibrous root is one main root, taproot is many e) Taproots and fibrous roots are essentially the same f) None of the above