Chapter 3 Plant roots

Storage parenchyma

cells of the cortex are thin-walled that can be used by the plant for storage of starch. (taproots can contain a great deal of what?)

elongation zone

cells that are produced by cell division enlarge by taking water into their vacuoles cell expansion propels the root tip through the soil.

Maturation zone

cells that have divided and elongated assume their distinctive roles.

Stele

collective term for all the tissues located inside of the endodermis (pericycles, vascular tissues, and some cases the pith)

Casparian strip

formed around endodermal cells where root hairs form.

Root hairs do what?

greatly increase the absorption potential of the root by several thousand times.

Epidermis

one cell layer thick. root epidermal cells do not have a thick cuticle (would interfere with water uptake)

What is the function of endodermis?

regulate root uptake of dissolved mineral nutrients

Contratile roots

roots contract to pull the shoot underground by expanding to the sides while contracting in length. (protects from fluctuations in air temperature)

Three layers of the cortex

exodermis, the storage parenchyma, and endodermis

Adventitious roots

roots that develop from organs other than the root (near or below the soil surface)

Order of the root structure in a cross section outside in?

Root hair, epidermis, cortex, endodermis, pericycle, xylem, phloem (and in monocots the pith).

Function of roots

1. anchor to provide support 2. absorb water and dissolved mineral nutrients and transport up the shoot. 3. Taproots sometimes used as storage of food reserves.

Where does root growth occur?

At the tips. Also the most active site of absorption.

Mucigel

Contains sugars and other compounds made by the golgi apparatus. This lubricates the pathway through the soil, protects the root from dessication, provides a pathway.

taproots

Developed from the radicle. What kind of roots can explore the soil at great depth to supply plant with water.

Seminal roots form where?

base of the first node in monocots

What is the function of the casparian strip?

blocks movement of water and dissolved minerals through the walls of endodermals cells forcing water and minerals to be taken up.

quiescent center

group of cells between the root cap meritstem and the zone of cell division

Exodermis

layer of suberized cells lying just beneath the epidermis. Function is prevent loss of water that has been absorbed by other parts of the root system to dry soil surrounding mature roots.

Root cap

like a thimble that covers and protects the growing root tip. (can also sense light)

cell division zone

located behind the root cap, source of new cells for root growth.

Pericycle

meristematic tissue one or more cell layers thick that is the origin of branch roots

Fibrous roots

shallow, numerous, and concentrated near the surface of soil (excellent at preventing soil erosion)

Endodermis

walls of these cells are wrapped with a band of suberin and lignin called the casparian strip.