Roots - Structure & Function Flashcards
What are the 3 main functions of the root?
Anchorage
Water uptake
Mineral uptake
Adapted root example for storage
Storage/perennation Daucus carota
Adapted root example for vegetative reproduction?
Dahlia ‘Bishop of Landaff’ rooted tuber.
Adapted root example for climbing?
Hedera helix ‘Glacier’ Advantitious roots grow from the stem and adhere to a vertical surface enabling plant to cling to the support and climb.
Adapted root example for support?
Prop roots on Zea Mays help to anchor the plants. Adventitious roots grow from the node at the base and spread to help anchor plant. A bit like guy ropes on a circular marquee!
What two types of root system are there?
Tap roots with laterals
and Fibrous roots
What are the four different types of roots?
Tap roots
Lateral roots
Fibrous roots
Adventitious roots
Where does the tap root develop from?
The radicle
What type of roots does a typical dicotyledons have?
Tap root and lateral roots.
What type of roots does a typical monocotyledons have?
Fibrous roots
Describe a tap root?
A primary root that develops from the radicle and becomes the dominant. Extends vertically down through the soil to access water where the soil does not dry out. Plants with a deep tap root don’t transfer well. Eg. Lathyrus odoratus . Some tap roots store food eg. Daucus carota. Only found in dicots!
What are lateral roots?
Extend horizontally from the tap root. Secondary roots grow sideways from the plant. Help to anchor the plant securely in the soil. Branching also increases surface area for water absorption. Only in dicots.
What are fibrous roots?
These grow from the base of the stem. Not developed from the radicle from another part of the plant. Therefore technically a type of adventitious root. No main central root, as the embryonic root dies back when plant is still young. Roots grow downwards and outwards to form a mass of fine roots all same thickness. Explore top soil much more effectively than tap roots, however much shallower rooting. More susceptible to drought. Only on MONOCOTS
Eg. Lolium perenne
Poa annua
Narcissus tete a tete
What are adventitious roots?
These grow from unexpected areas eg. the stem or other plant organ. in monocots the primary roots are short lived, and replaced by adventitious roots. (fibrous roots).
Roots which grow from stolons of Fragaria x ananassa
Prop roots on Zea Mays
Side roots on aerial stems of Hedera Helix glacier
New roots that form on stem cuttings.
What is the endodermis?
The inner most layer of cortex. Closely packed cells. The control point for water and selective mineral uptake.
What is the casparian strip?
A waxy band around the endodermal cell wall which forces water and dissolved minerals to pass across the cell membrane and into the endodermal cell rather than between the cells and through the cell wall.
What is a root hair?
A root hair is one epidermal cell with a protrusion.
It is not a lateral root.
Is is a single specialised epidermal cell.
What are the 12 features of a root?
- Root cap
- Apical Meristem
- Zone of elongation
- Zone of differentiation
- Root hairs
- Epidermis
- Cortex
- Endodermis
- Pericycle
- Phloem
- Xylem
- Vascular cambium. (not present in monocots)
What is the function of the root cap?
Thimble like cup over the root tip. High turn over of cells, as under a lot of pressure to push through the soil but cells constantly replaced.
Protects the growing root tip.
Secretes mucilage to lubricate the root tip and protect it.
Describe the apical meristem and it’s function?
Dome shaped area of meristematic cells with prominent nuclei, constantly dividing.
Function is to produce new cells.
Describe the Zone of elongation and it’s function?
Cells elongate by filling their vacuoles with water. Most elongation of the root takes place here. Cells are undifferentiated. (not specialised).
It’s function is to push the root cap and meristem through the soil. When elongation ends, differentiation begins.
Describe the zone of differentiation and it’s function?
Root hairs are formed here.
Specialised tissues develop - xylem, phloem, cortex, endodermis.
Cells here do not elongate. They differentiate.
Root hairs form for water absorption..
Lateral roots grow from the pericycle.
Xylem cells thicken and die.
Describe a root hair and it’s function?
Root hairs are a single epidermal cell with hair like projections. Water and Mineral absorption by increasing the surface area.
Describe the epidermis and it’s function?
1 cell thick layer dermal cells. Lacks cuticles in roots. Covers all root except cap.
Protects underlying tissue.
Absorbs water and dissolved minerals.