Rhs year 1 week 4 2011
Transcript of Rhs year 1 week 4 2011
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RHS Level 2 Certificate
Year 1 Week 4
Parts of the Plant
Roots
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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.
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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.
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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).
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Root structure
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Types of Root
Primary rootSecondary rootTap rootFibrous rootLateral rootAdventitious roots
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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
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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.
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Parts of the root – cross section
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Parts of the Root
Root cap
Root tip
Root hairs
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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.
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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
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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.
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Root adaptations – very wet and very dry. Which is which?
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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.
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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