Lecture 13 - Roots

Major Root Functions

• Anchoring / stabilization in soil

• Water/nutrient uptake through absorption

• Conduction of materials throughout the plant

• Stores absorbed materials

Tap Root System

One prominent main root with several branching roots

Fibrous Root System

Many different roots of equal size arising from stem base

Monocot system

fibrous

Eudicot system

Taproot

RAM produces

The roots!

Growth zones in root

Zone of maturation

Zone of elongation

Zone of division

Zone of maturation

Here, cells differentiate into specific fates

Zone of elongation

Cells elongate

Zone of Cell Division

Where cells divide, including meristem by mitosis

Root cap

Protection of meristematic tissue

Root hair

Ext. of root epidermal cell that increases root absorptive capacity in maturation zone

Quiescent center / QC

relatively inactive area of RAM containing initials

Label root zones

Label root structure

plant root XS label

plant XS root label

root LS label

Eudicot root

X+P form a solid mass in the center of root known as vascular cylinder

Monocot root

Central pith, surrounded by ring of vascular tissue

identify root type

Eudicot

identify root type

Monocot

identify

eudicot root

identify

monocot root

Eudicot root epidermis

• protects root

• root hairs absorb water/dissolved minerals

Eudicot root cortex

• consists of parenchyma cells

• starch storage

Eudicot root vascular tissue

X+P surrounded by pericycle and endodermis

label eudicot root

endodermis

innermost layer of cortex that prevents water/dissolved materials from entering xylem

• contains casparian strip

identify root

monocot

symplastic water movement

water movement through cells / intracellular

apoplastic water movement

movement through porous cell walls or between cells, not through/inside PM

label water movement types

What causes water movement through endodermis?

Casparian strip

casparian strip

Band of waterproof material around radial/transverse cell walls of endodermis, ensures that water only enters xylem by passing through endodermis interior

pericycle

layer of cells just inside root endodermis, outermost layer of vascular tissue

this is where lateral roots emerge

lateral roots

pushes through cortex and epidermis to emerge

forms same meristems, tissues and zones as primary root

Adventitious roots

roots developed from the stem

also known as prop roots

Mycorrhiza

Mutually beneficial association between fungi and root that helps plant absorb minerals

Nodule

Small swelling on root of leguminous plant, nitrogen fixing bacteria (Rhizobium) present