Roots structure and function

What makes up the roots. STRUCTURE + FUNCTION

> Epidermis - Thin cuticle for absorption, root hairs increase surface area function: roots Absorb minerals and water >Root hairs - Extension of epidermal cells, short-lived, zone of maturation. Function: Increase absorptive surface area and absorption of water and ions. > Cortex - Storage with prominent amyloplasts, Circulation of atmosphere (gas exchange) with prominent intercellular spaces, Function: Control water flow into the vascular cylinder with endodermis. Cortex Ground tissue system of parenchyma located between the epidermis and vascular cylinder. > Endodermis - Densely packed parenchyma cells with Casparian strips along top, bottom, and side walls made of a waxy hydrophobic substance called suberin. Function Controls water flow into the vascular cylinder. >Pericycle - 1 - several layers of parenchyma cells, can give rise to more layers of pericycle. Gives rise to lateral roots (branch roots), contributes to vascular cambium (layer between xylem and phloem), and gives rise to the cork cambium (AKA phellogen) and periderm >Vascular system: Xylem & Phloem -

Lateral roots

Branch roots. Endogenous (inside origin) formation: lateral roots form deep within the root itself, originate in the pericycle, punch their way through endodermis, cortex, and epidermis.

FUNCTION for the plant:

Functions of the plant root system include: 1. Anchorage and support. 2. Absorption and conduction. 3. Storage. 4. Photosynthesis. 5. Aeration. 6. Movement 7. Reproduction.

Movement

In many bulb- and corm-forming plants, contractile roots pull the plant downward into the soil where the environment is more stable.

Aeration

Plants that grow in stagnant water or other watery places have modified roots called pneumatophores to which oxygen from the air diffuses.

Taproot system

Primary root is long lived: it grows deep and numerous lateral branches form off it. Secondary growth is common. Found in gymnosperms and dicots.

Fibrous root system

Primary root is short lived. Roots form a dense network of: adventitious roots and lateral roots. Shallowly rooted. Strongly binds soil. Secondary growth absent.

Photosynthesis

Some roots are capable of performing photosynthesis, as in the epiphytic orchids.

Absorption and conduction.

The plant root system absorbs water, oxygen and nutrients from the soil in mineral solution, mainly through the root hairs. They are capable of absorbing inorganic nutrients in solution even against concentration gradient. From the root, these are moved upward. Plants with a fibrous root system are more efficient in absorption from shallow sources.

Reproduction

The plant root system also serves as a natural means of perpetuating a species.

Anchorage and support.

The plant root system anchors the plant body to the soil and provides physical support. However, taproot system provides more effective anchorage such that they are more resistant to toppling during storms.

Storage

The root serves as storage organ for water and carbohydrates Fibrous roots generally store less starch than taproots. Some roots are capable of storing large amounts of water; the taproots of some desert plants store more than 70 kg of water