Outline Definition characteristics of a root Why are roots
important? Contributors to Root Growth Parts of a Root Regions of
Root Anatomy of the root Differences between dicot and monocot
roots Types of roots Modifications of root Functions of roots
Task
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Definition Plant morphology: The study of the forms and
structures, especially their external form. The study of forms and
features of different plant organs such as roots, leaves, flowers,
seeds and fruits Physiology: the branch of biology concerned with
the vital functions of plants such as nutrition, respiration,
reproduction, etc.
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What are the characteristics of a root? The descending portion
of the axis of the plants Is not normally green Does not commonly
bear buds except in Batatas. Ends in and protected by root cap.
Bears unicellular hairs Lateral roots always develop from an inner
layer pericycle - Endogenous
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Why are roots important? Roots may make up over half of the
body of a plant. They anchor the plant to the ground From the soil
they absorb water and minerals the plant needs
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Contributors to Root Growth Roots grow in length only at the
tips. they grow where moisture occurs, moisture is not only
requirement for their growth. Sugar produced in the leaves by
photosynthesis is also necessary, hormones necessary, which are
also produced in the leaves. Hormones must be transported from the
leaves to the roots in order to influence root growth.
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Temperature the presence of minerals acidity or alkalinity are
other important factors in both root and plant growth. In addition
to moisture, air in the soil is also significant
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Parts of a Root Roots supports the plant and absorb, transport,
and store nutrients. Like other plant parts, root contain all three
tissue system 1. Vascular 2. Ground and 3. Dermal
Dermal Tissue System Plants dont have skin, have a system of
dermal tissue and protects it in a variety of ways. Dermal tissue
called epidermis is made up of live parenchyma cells in the
non-woody parts of plants. On leaves and some stems, epidermal
cells may secrete a wax-coated substance that becomes the cuticle.
Dermal tissue made of dead parenchyma cells makes up the outer bark
of woody plants.
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Ground Tissue System Dermal tissue surrounds the system of
ground tissue, which makes up much of the inside of a plant. Ground
tissue provides support and stores materials in roots and stems. In
leaves, ground tissue is packed with chloroplasts, where
photosynthesis makes food for the plant.
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The ground tissue system consists of all three of the simple
tissues 1. parenchyma tissue 2.collenchyma tissue 3.and
sclerenchyma tissue Parenchyma is by far the most common of the
ground tissues.
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Vascular Tissue System Surrounded by ground tissue, the system
of vascular tissue transports water, mineral nutrients, and organic
compounds to all parts of the plant. Plants can transport necessary
fluids and nutrients throughout their systems. A plants vascular
system is made up of two networks of hollow tubes somewhat like our
veins and arteries.
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Each network consists of a different type of vascular tissue
that works to move different resources throughout the plant. Xylem
(ZY-luhm) is the vascular tissue that carries water and dissolved
mineral nutrients up from the roots to the rest of the plant.
Phloem (FLOH-EHM) is the vascular tissue that carries the products
of photosynthesis through the plant.
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In the center of the root is the vascular cylinder, which is
made of xylem and phloem tissues. The vascular cylinder is
surrounded by ground tissue, covered by dermal tissue. A plant
absorbs most of its water in the dermal tissue just above the root
tips. These cells have tiny projections called root hairs, Root
hairs find their way through the spaces between soil particles,
greatly adding to the surface area available to take up water.
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Covering the tip of the root is the root cap, a small cone of
cells that protects the growing part of the root as it pushes
through the soil. Just behind the root cap is where most of the
roots growth occurs. Groups of cells that are the source of new
cells form tissue called meristem. Meristem cells arent
specialized, but when they divide, some of the new cells specialize
into tissues.
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Regions of Root
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Regions of the Root
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Regions of the root 1. Root cap: protects the tender apex of
root outer parts of the root cap wears away newer cells formed by
underlying tissue are added to it. Absent is aquatic plants
2.Region of Cell Division: lie within and little beyond the root
cap few mm in length cells very small, thin walled & contain
dense mass of protoplasm cells under go repeated division-
meristematic region
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3. Region of elongation: above meristematic regions, 1-5 mm in
length rapid elongation and enlargement growth in the length of
root 4.Region of maturation: few mm to few cm in length region
produce cluster of very fine thread like str.- Root hairs absorb
water & minerals salt from the soil Internally the cells in
this region undergo maturations and differentiation various kinds
of primary tissues.
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Root Hairs Meristematic activity, which increases the length of
the root, occurs only at the tip. When the cells here divide, they
produce the new root cells and root cap cells. The root cap cells
are sloughed off as the root grows through the soil. The epidermal
cells produce root hairs a short distance above the tip. Root hairs
are part of epidermal cells.
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Root hairs
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Anatomy of the root Epiblema Exodermis Cortex Endodermis
Pericycle Conjuctive tissue Protoxylem Metaxylem Phloem Pith
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Dicot RootMonocot root
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Structure cross section of a root in a region where only
primary growth has occurred
Dicot and monocot roots MonocotDocot Numerous vascular
bundlesVary fron 2-4 rarely 6 Cambium is absentCambium appears as
secondary meristem at the times of secondary growth Xylem vessels
are large, more or less circular Smaller and polygonal in shape
Secondary growth is absentDevelops after the cambium
develops/appears pith is well developedSmall or absent Pericycle
gives rise roots onlyGives rise to lateral root and cambium The
inner walls of the endodermis are considerably thickened to give
U-shaper appearance Thickening is not prominent and is due to the
presence of casparian strips
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Casparian Strip Special thickened band present on radial and
tangential walls of the endodermal cells. lignin and suberin
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Types of Roots In majority of the dicotyledonous plants, the
direct elongation of the radicle leads to the formation of primary
root which grows inside the soil. It bears lateral roots of several
orders that are referred to as secondary, tertiary roots. The
primary roots and its branches constitute the tap root system, as
seen in the mustard plant
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Types of Root Tap root Root Systems: Arise from radicle
Adventitious Roots: arise from anything other than the radicle
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In monocotyledonous plants, the primary root is short lived and
is replaced by a large number of roots. These roots originate from
the base of the stem and constitute the fibrous root system, as
seen in the wheat plant. In some plants, like grass, Monstera and
the banyan tree, roots arise from parts of the plant other than the
radicle - adventitious roots.
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Modifications of Root Tap Roots Roots in some plants change
their shape and structure become modified to perform functions
other than absorption and conduction of water and minerals. They
are modified for support storage of food and respiration. Tap roots
of carrot, turnips and adventitious roots of sweet potato, get
swollen and store food.
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Prop roots- Provide additional supports to plant. Eg. banyan
tree Stilt roots the stems of maize and sugarcane have supporting
roots coming out of the lower nodes of the stem. Pneumatophores
Rhizophora growing in swampy areas, many roots come out of the
ground and grow vertically upwards. help to get oxygen for
respiration.
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Prop root. E.g Banyan
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Aerial Roots Plant attaches itself to tree branch Roots hang
down in mid-air and absorb water from rainfall Examples Some
Orchids
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PROP ROOTS e.g. Corn
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STILT ROOTS e.g. Mangrove
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Adventitious Roots Grow from unusual places on plants such as -
Stems.
Slide 42
Slide 43
Functions of Roots The main functions of the root system are
absorption of water and minerals from the soil, providing a proper
anchorage to the plant parts, storing reserve food material and
synthesis of plant growth regulators of some plants can be used to
grow a new plant
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Task Explain the following modifications of root and state
their functions: 1. Tap root: Fusiform, napiform, conical and
tuberous. 2.Branched root: Pneumatophores. 3. Adventitious root: a.
tuberous, fasciculated, nodulose, moniliform and annulated root. b.
prop root, climbing root, Buttress root, haustoria, respiratory
root and epiphytic root