Rhs year 1 week 4 2011

RHS Level 2 Certificate

Year 1 Week 4

Parts of the Plant

Roots

Learning objectives

1.2 Parts of the plant – an overview1.2.1 State the parts of a typical seed bearing plant and their

respective purposes.1.3 Roots.(1) 1.3.1 Describe how the root system develops from the radicle.1.3.2 Define the meaning of ‘primary’, ‘secondary’, ‘tap’, ‘lateral’,

‘fibrous’, and ‘adventitious’ roots.1.3.3 Describe the external structure of the root tip and the role of

the root cap and root hairs.1.3.4 Describe how the root is adapted in order to perform specific

functions.1.3.5 Root fungi - symbiosis1.3.6 Describe transverse sections of the young dicotyledon root;

these should include the location of the following: epidermis, cortex, xylem, phloem, pith, cambium, vascular bundles, endodermis, pericycle, cuticle.

Parts of a seed bearing plant

Review the parts of a plant Introduction to their function We will look at each in turn over the next few

weeks – to understand how to grow plants effectively it is important to know how they work.

Roots

What do roots do?– Provide support and anchorage for most

plants (not floating aquatics!) Absorb water and nutrients from the soil

(by osmosis) Store food to allow the plant to survive

periods of dormancy – for example carrots (Dacus carota) and parsnips (Pastinaca sativa).

Root structure

Types of Root

Primary rootSecondary rootTap rootFibrous rootLateral rootAdventitious roots

Parts of the Root

Radicle – first root on germination Root cap – protective, disposable cells

covering root tip Root hairs – adapted epidermis cells, absorb

water and nutrients Cortex – packing cells, protect other tissues

and store carbohydrates Pericycle – meristem, produces branching

roots and thickening growth

Parts of the root

Root tip – root apical meristem Epidermis – ‘skin’ or bark of the root Endodermis – layer of cells outside the pericycle that

control entry and exit of water and dissolved nutrients

Xylem – carries water and dissolved nutrients from the roots to the tip of the shoots

Phloem – carries dissolved sugars and carbohydrates etc from the leaves to where they are needed.

Parts of the root – cross section

Parts of the Root

Root cap

Root tip

Root hairs

Root development

Radicle (first root produced at germination) – rapid cell division at root apex meristem, production of root hairs and subsequently branching root development from the pericycle (lateral meristem of the root).

Root branches in turn grow, produce root hairs and further branches.

Root adaptations – adventitious roots

Adventitious roots – develop from leaf nodes or from damage to the stem. Here adventitious roots on a Swiss Cheese Plant (Monstera deliciosa) enable the plant to climb

Root adaptations – food storage

Adapted cortex (parenchyma) cells store carbohydrates. Carrots (Daucus carota) are biennials; food made in the first year is stored for use in the second when the flowers and seed are produced.

Root adaptations – very wet and very dry. Which is which?

Symbiosis – working together.

Nitrogen fixing – bacteria that live in nodules on the roots of legumes (peas, beans, some trees) convert nitrogen gas into compounds that plants can use.

Mycorrhizal fungi – connect to roots (particularly trees) and take carbohydrate and water and give nutrients, especially potassium.

Learning outcomes -review

1.2 Parts of the plant – an overview1.2.1 State the parts of a typical seed bearing plant and their respective

purposes.1.3 Roots.(1) 1.3.1 Describe how the root system develops from the radicle.1.3.2 Define the meaning of ‘primary’, ‘secondary’, ‘tap’, ‘lateral’,

‘fibrous’, and ‘adventitious’ roots.1.3.3 Describe the external structure of the root tip and the role of the

root cap and root hairs.1.3.4 Describe how the root is adapted in order to perform specific

functions.1.3.5 Root fungi - symbiosis1.3.6 Describe transverse sections of the young dicotyledon root; these

should include the location of the following: epidermis, cortex, xylem, phloem, pith, cambium, vascular bundles, endodermis, pericycle, cuticle