ROOT SYSTEM

ROOT IS AN underground cylindrical part of the plant which develops from radicle and grows vertically downward into the soil.

characteristics

Roots are cylindrical structures. Root is positively geotropic. Buds and leaves are absent. Root is colourless due to absence of

chlorophyll. Root cap is present over the apex.

Third Chapter Plant OrgansSection One Roots

Organ Ones that are formed by many kinds of

tissues , having certain external shape and inside structure and plant body component of carrying out certain physiological function .(review tissue)

vegetative organ (root ,stem ,leaf) Organ reproductive organ(flower ,fruit ,seed)

Tissue The source similar to the function is the same ,

shape structure and the cell group contacting each other closely is called the tissue.

Vegetative organ : Absorb playing , make and supply the body nutriment function of the plant , making the plant body grow , development with. Including the root , stem , leaf.

Reproductive organ :Play a role in breed the later generation and extend ethnicallying. Including the flower , fruit , seed.

absorb function transportation supportion Physiological function breeding preservation assimilation function

Medicinal value

Radix

Ginseng

Radix

Notoginseng

Radix

Astragali

Radix

Ophiopogonis

Part One Forms and Types of Roots

★Forms of Roots★ Root Types1 Main root and lateral root 2 Normal root and adventitious root

Types of Root system

tap root system and fibrous root system

4 Abnormal root storage root fleshy tap root

root tuber prop root aerial root climbing root water root parasitic root

1. Coniform root 2. columniform ～ 3. pelletly ～

4. Spindly root tuber 5. nubby root tuber

1.Prop root 2.aerial root 3.climbing root 4.5.parasitic root

Part Two Inner Structure of Roots Basic Structure of the Root Tip Root cap Region of Division Region of Elongation Region of Maturation

Basic Structure

of the Root Tip

1.Maturation zone

2.Elongation zone

3.Meristematic zone

4.Root cap

Primary Structure Epidermis

exodermis

Cortex cortex parenchyma endodermis casparian dots

passage cell

Primary Structure of Dicotyledon Radicle

1.Epidermis

2.Cortex

3.Endodermis

4.Pericycle

5.Protoxylem

6.Metaxylem

7.Primary phloem

8.Immature metaxylem

Ⅰ.solid view of endodermis cells （ show casparian strip ）

Ⅱ.transverse section view of endodermis cells （ show casparian dots ）1.Cortex cell 2.endodermis 3.casparian strip 4.pericycle

Casparian dots or casprian strip

Passage cell

Vascular cylinder pericycle

primary xylem (diarch , triarch ,

tetrarch,hexarch,polyarch,etc)

primary phloem ☆Definition : Exarch: The order of differentiation and maturation of

primary xylem of root is from the outside to inside, and is known as exarch.

Formation of Lateral Root

Transverse section

of horsebean root

1 、 endodermis

2 、 pericycle

Formation of lateral root

Secondary Structure of Roots

①Origin and Activities of the Vascular Cambium

Cambium secondary phloem

secondary xylem

Ⅰ.radicle （ dot and line show beginning place of cambium ）

Ⅱ.cambium becomes consecutive tissue

Ⅲ.whole cambium make secondary structure

Ⅳ.cambium becomes a ring

1.Primary xylem 2.primary phloem 3.cambium

4. secondary xylem5.secondary phloem

The transverse section of MaDouLing

Ⅰ. （ 1.phellem 2.phellogen 3.cortex 4starch grain 5.secretory cell）

Ⅱ. （ 1.phloem 2.sieve tube gang 3.cambium 4.ray 5.xylem）

Ⅲ. （ 1.xylem 2.ray）

Secondary structure of root

②Origin and Activities of the Cork Cambium Phellogen phellem phelloderm

Periderm and lenticel1.Origination of phellogen 2.epidermis

3.phellogen 4.phellem 5.phelloderm 6.cortex parenchyma7.supplementary cell

Anomalous Structurethe model sketch of root anomalous structure

Ⅰ.shanglu root

Ⅱ.niuxi root

Ⅲ.chuanniuxi root

Ⅳ.heshouwu root

1.Phellem

2.Cortex

3.Phloem

4.Cambium

5.xylem

Symbiosis PhenomenonRoot Nodule and Mycorrhiza