This presentation gives a clearly overview of the basic or primary organs of plants; roots, stem, and leaves and their role in the plant's body.

1. FASAMA HILTON KOLLIE
BSc. Bio, Mother Patern College of Health Sciences (MPCHS)
ᴓ1
Chapter Four
Email - fkollie25@gmail.com

2. CHAPTER OUTLINE
1. Overview of vascular plant Organs
2. Overview of plant growth and development
3. Primary plant body
(ROOTS, STEMS & LEAVES)

3. CHAPTER OBJECTIVES
 Have an idea of the basic plant organs
 Describe the structure of a root, stem and leaves
 Know the general functions of roots, stems and leaves

4. • Plant organs are made from simple and complex tissues that
adapts as a group to perform particular functions.
• Vascular plants have three types of organs: Root, Stem &
leaves
• Bryophytes and some seedless vascular plants have
structures that can be called stem-like, leaf-like and root-
like but are not consider true root stems and leaf.

5. • Any part of a plant that supports leaves or
reproductive structures
• Stems vary greatly in size, such as a slender
stalk supporting a small flower
• Regardless of size, all stems display leaves in
the best position for photosynthesis
• Stems provide pathways for the transport of
leaves products to roots

6.  Leaf is the main photosynthetic organ of
modern plants
 Leaves serve as the site of photosynthesis
 They are an extension of the plant’s
vascular tissue system
 Leaves do not only conduct water but also
provide most of the pressure that actually
forces the water through the plant’s body

7. • Root has two main functions:
– Anchoring the plant in the soil
– Absorption of water and minerals
• Absorption takes place near the tips of roots
through trichomes called root hairs
• Many roots store food for the plant. Eg: carrot
and sweet potatoes

8.  Plants and other multicellular organisms develop from a
single cell
 Through cells division, elongation and specializing for
different functions
 Seed plants are either gymnosperms or angiosperms

9.  Gymnosperms are plants with “naked
seeds”
 Angiosperms are plants with “seeds in
a container”
 The body of a typical plant can be
described as having two connecting
systems:
Root system
Shoot system

10. • Plant embryogenesis - is the process that produces a plant
embryo from a fertilized ovule by cell division and the
differentiation of undifferentiated cells into tissues and
organs.
• A seed plant embryo includes the following embryonic
organs that develops into a root and shoots: Cotyledon,
Radicle, Plumule, Epicotyl and Hypocotyl
PLANT EMBRYOLOGY

11. • “seed leaves”
• It is usually the largest and most
visible parts of an embryo
• Consist of one or more seed leaves
• Main function: Stores food for the
germinating seed
Plant Embryology

13.  “Embryonic root”
 the part of a plant embryo that
develops into the primary root
Plant Embryology
 “Embryonic shoot”
 The rudimentary shoot of
an embryo plant

14.  “Embryonic stem”
 The tiny shoot, which develops
into stems, leaves and flowers of
the plant future
Plant Embryology
 The stem of a germinating
seedling, found below the
cotyledons and above the
radicle

16.  Plants that have significant secondary growth are know informally
as Woody plants
 Plant with little or no secondary growth are know as Herbaceous
plants
 Plants have indeterminate growth
 Plant can be categorized into three distinct groups based on how
long they live:
Annual, Biennial and Perennial plants
Plants Growing Seasons

17. • An annual is a plant that completes its life cycle during a single
growing season
• Eg: Marigolds, beans, corn etc
Annual Plants

18.  A Plant that usually requires two growing seasons (2 years) to
complete its life cycle
 Eg: Carrots, beets, cabbage etc
Biennial Plants

19.  A plant that grows for more than two years
 Most are woody plants
 Eg: trees, shurbs
Perennial Plants
Evergreen Tree Dragon blood tree

21. • The body of a typical plant can be
described as having two connecting system:
a root system and a shoot system
• The root system consists of all the roots,
which are usually below the ground
• The shoot system consists of all the stems,
leaves, and reproductive structures, which
are usually aboveground

22. • In vascular plants, the root is the organ of a plant that typically
lies below the surface of the soil.
• Roots can also be aerial or aerating, that is growing up above
the ground or especially above water.
• The first root that comes from a plant is called Radicle

23. • FUNCTIONS OF ROOT
– Anchoring of plant firmly in the soil
– Absorption and conduction of water and inorganic nutrients
– Storage of food and nutrients
– Vegetative reproduction
– Root produce hormones and other substances that regulated the
plant’s development and structure

24. • On the basis of their origin there are two main
patterns of root growth:
– Taproots system
– Adventitious root systems
TYPES OF ROOT SYSTEM

25. • The taproot is the largest, most central, and most
dominant root from which other roots sprout
laterally
• A taproot is somewhat straight and very thick
• This root function to tap deep sources of water
• It develops directly from the radicle
• Taproot produces branch roots called lateral roots

26. • Taproot system are typically of most dicots and gymnosperms
• Eg: Dandelion, Beans, Cycads, Conifers

27. • Roots that develop from any other part of a plant body
either than the radicle
• This is common in seedless vascular plants and grasses
• These roots can be present underground or above the
ground.
• No single root stands out as the largest root in a fibrous
root system
• Fibrous roots grow fairly close to the surface of the
ground
• few plants with fibrous root systems: Coconut palm,
Grass, Onion

30. • Root development occurs near the root tip, in the apical meristem
• Apical meristem has cells called Initials
• Initials are located within small spherical center of the meristem called
Quiescent center
• Initials and derivative cells can rebuild damaged or destroyed apical
meristem

31. • A root apical meristem produces a root cap which consist of
several layers of cells
• The root caps serves as a protection for the root cells as it pushes
between the soil particles
• The root cap produce slimy polysaccharide know as Mucigel
• Mucigel lubricates the passage of the root through the soil

32. The root apical meristem

33. • Cell division in a root or shoot apical meristem produces the derivative that becomes
the Primary meristems: protoderm, ground meristem and procambium
• In a root, division, growth, and differentiation of cells can be traced linearly
through three overlapping regions;
−

35. Zone of Cell Division, Elongation and Maturation

36. • In a cross section or transverse section, the root presents the following structures:
– Stele
– Protostele
– Epidermis
– Cortex
Stele:
• The central part of a root or stem
• The zone internal to the endodermis which contains specialized tissue responsible
for the transport of water and minerals to the shoot
− Endodermis
− Pericycle
− Vascular tissues

37. Epidermis
Cortex
Endodermis
Pericycle
Xylem
Phloem
Stele
Root hair

38. • Protostele: is the most simplest type of stele and the earliest to evolve
• In the root of most seed plants, two important cell layers called the
pericycle and the endodermis surround the stele
• Pericycle: a cell layer immediately encircling the stele that gives rise to
lateral roots
• Endodermis: the layer of cells around the stele that regulates the flow
of substances between cortex and vascular tissue

39. A
B
C
D
E
F
G

40. • Roots carry out the following functions in addition to their
primary functions:
• A modified adventitious root that arise from
stem tissue
• Found in plants that grow on other plants for
support and nourishment (Epiphyte)
• Provides additional support for a plant such as
water retention, photosynthesis, and support.
• Eg: Corn

41. • Flared roots that extend from tree trunks
• Provide stability to plants in thin soils
• Eg: Fig tree

42. • A thickened specialized root at the
base of a corm, bulb, rosette or
other organ
• Contractile roots are usually broad,
fleshy, vertical, tapering, wrinkled
looking
• It is designed to shrink vertically
under conditions of seasonal
drought that helps position this
plant part at an appropriate level in
the ground.
• Found in lilies

43. • Also known as air roots
• They provide oxygen for plants in swampy areas where high rate of
aerobic decay reduces the oxygen supply in the water
• Eg: Mangrove

44. • Modified parasitic roots
• They penetrates the stems and roots of other plants to obtain water,
mineral and organic molecules
• Eg: Mistletoe (Viscum album)

45. • Roots often form mutualistic or beneficial associations with other
organisms
• Mycorrhizae
• This is a form of mutualistic relationship between vascular plant roots
and soil fungi
• This occur in more that 90% of plant species
• The two main types of these associations are; Endomycorrhizae
and Ectomycorrhizae

47. S S

48. • A part of a plant that supports leaves or
reproductive structures
• They may vary in size, such as from a slender
stalk to a big tree trunk
• They grow above the ground and together with
the leaves they constitute the shoot system
• First stem of a plant develops from part of a
seed embryo called Epicotyl

49. − Transport water and solutes
between roots and leaves
− Produces & support appendages of
plant (leaves, flowers, fruits)
− Stems in some plants are
photosynthetic
− In some plants, stems have become
adapted for specialized functions
such as;
 Storage etc
Cauti

50. Herbaceous Stems
• Soft & green
• Little growth in
diameter
• Tissues chiefly primary
• Chiefly annual
• Covered by epidermis
Woody Stems
• Tough & not green
• Considerable growth in
diameter
• Tissues chiefly secondary
• Chiefly perennial
• Covered by corky bark

51. Herbaceous Stem Woody stem

52. All stems are recognizable from other plant organs by the
presence of nodes, internodes, buds and leaves
− Node: A node is a point on the stem from which leaves
or buds arise
− Internode: The portion between two successive nodes
− Buds: A bud is an undeveloped or embryonic shoot
which has the potential for further plant growth.
−It may develop into a leaf, flower, or both.
−Plants have three types of buds on the basis of location,
namely: Terminal buds, Axillary buds and Adventitious
buds

54. • Internal structure of a dicot stem reveals the following features:
Epidermis, cortex, pericycle, vascular bundles and pith

55. • Two models describes how a shoot apical meristem gives rise
to the primary meristems
• These are: The Zone model and the Cell-layer model
• Here the shoot apical meristem is divided into three regions:
(central mother cell zone, peripheral zone, and pith zone)
A. Central mother cell zone; consist of cells that divide not
frequently and give rise to peripheral and pith zone

56. B. Peripheral zone; form a 3D ring around
the central mother cell zone
• Cells from this zone develop into the leaf
primodial
• Eventually, this gives rise to the dermal and
vascular cells of the stem
C. Pith zone; it is below the central and
peripheral zone
• Cells of the pith zone give rise to the ground
tissue in the center of the stem
• Ground tissue are in the pith.

57. • Also known as the Tunica Corpus model.
• This consist of two layers: Outer layer (Tunica) and
the Corpus layer.
• The outer layer (Tunica) is equivalent to the
peripheral zone
• Here the plant divide perpendicular to the surface
known as the anticlinal division.
• The Corpus layer is equivalent to the central mother
cell zone, the inner part of the peripheral zone and
the pith zone
• The corpus give rise to the procambium and ground
meristem while the tunica give rise to the
protoderm.

58. • Leaves on the side of the shoot meristem comes
in three basic patterns; (alternate, opposite and
whorled)
• Alternate arrangement has one leaf per node, it
may form a spherical or helical pattern
• Opposite arrangement consists of two leaves per
node. Each pair of leaves is oriented like the
previous pair
• Whorled arrangement includes three or more
leaves per nodes.

59. • Specialized stems are: Stolon, rhizomes, tubers, bulbs, corms etc
• Horizontal stem aboveground
• Stolon often originate as axillary buds
• They help a plant reproduce asexually
• Eg: Bermuda grass, spider plant, ferns
• Underground horizontal stems with
adventitious roots
• hizomes are used to store starches and
proteins
• Eg: Irises, ferns, grasses, ginger

60. • Underground stems that store
food
• Usually swollen
• The “eyes” of a potato (Irish
potatoes, Solanum tuberosu)
are the nodes of a starch-
ladened stem
• Large buds with a small stem
at the lower end surrounded
by numerous fleshy leaves
• Leaves stores nutrients
• Adventitious roots at the
base
• Eg: Onion, tulip, daffodil and
Lily
• Composed entirely of stem
tissue surrounded by a few
papery scale like leaves
• Adventitious roots at the
base
• Eg: Crocus and gladiolus

61. S

62. • A leaf is a thin, flattened organ,
above ground and specialized
for photosynthesis
• It originates from the shoot
apical meristem as a bump of
tissue know as the leaf primordia
• Leaf primordium develops into a
leaf through cell division, growth,
and differentiation

63. • Photosynthesis is the primary function
of the leaves
• It function in water retention in desert
plants. Eg: Cactus
• Function during transpiration
• Function in translocation via the leaf
veins

64. • A leaf can be either simple
leaf or compound leaf
• This concept is determined by determining
the position of the bud
• A simple leaf is a single leaf that attaches to
the stem
• Simple leaf contains one blade.
• A compound leaf is a leaf that is composed
of two or more leaflets on a common stalk
• Blade is divided into two or more distinct le
aflets.

66. • Leaves can be found in a variety of shapes
and sizes
• Most leaves are broad, flat and typically
green in color
• Leaf shape is adapted to best suit the
plant's habitat and maximize photosynthesis.
• The Basic leaf features of plants include:
• Leaf blade
• Petiole
•Stipules
Tip
Midrib
Margin
VeinPetiole
Blade (Lamina)

67. BLADE
• The broad portion of a leaf.
– Apex - leaf tip.
– Margin - leaf edge boundary area.
Margins can be smooth, jagged
(toothed), lobed, or parted.
– Veins - vascular tissue bundles that
support the leaf and transport
nutrients.
– Midrib - central main vein arising
from secondary veins.
– Base - area of the leaf that connects
the blade to the petiole.

68. • PETIOLE - thin stalk that attaches the leaf to a stem.
• STIPULES - leaf-like structures at the leaf base.
• Leaf shape, margin, and
venation (vein formation)
are the main features used
in plant identification

69. • Leaf tissues are composed of layers of plant cells
• Different plant cell types form three main tissues found in leaves
• A typical leaf has three regions, namely: Upper epidermis,
Mesophyll tissue layer and Lower epidermis
• Mesophyll tissue layer is sandwiched between the two layers of
epidermis
• The vascular tissues of a leaf is located within the mesophyll layer
as well as ground tissues
• The dermal tissues are found in the epidermal region of a leaf

70. 1. EPIDERMIS
• It is the outer layer of a leaf
• It is a single layer of cells derived from the protoderm
• Epidermis protects the leafs from water loss, abrasions
• It also regulates the exchange of gases and water vapor from the
plant via the leaves
• It is usually non-photosynthetic
• It secretes a waxy coating called cuticle that helps the plant retain
water
• It has tiny pores called Stomata
• Guard cells regulates the opening and closing of the stomata

72. 2. MESOPHYLL
• The middle mesophyll leaf layer is composed of a Palisade mesophyll and
a Spongy mesophyll
• Palisade mesophyll contains columnar cells with spaces between the cells
• Most plants chloroplast are found in this region
• Spongy mesophyll is located below the palisade mesophyll
• It is composed of irregular shaped cells
• Leaf vascular tissue is found in spongy mesophyll

73. • Like other organs, leaves are often modified for functions other
than photosynthesis. Below are a few examples:
• Insect-trapping leaves
• Leaves modified for
reproduction
• Prophylls
• Cotyledons
• Tendrils
• Stipule
• Spines
• Storage leaves

74. • A tendril is a specialized leave or
petiole with a threadlike shape
• It is used by climbing plants for
support, attachment
TENDRIL STIPULE
• An outgrowths borne on either side of
the base of a leafstalk
• They are used like leaves to make energy
for the plants.
• Sometimes stipules protect the next leaf
or bud as it grows in, then falls off after
the leaf unfolds

75. INSECT-TRAPPING LEAVES
• Insect-trapping leaves are leaves that are
specialized to trap insects.
• They may be sticky to trap the insect, may
form containers or they may snap shut when
the insect lands on the leaves.
SPINES
• Spines are hard, sharp leaves that are
specialized to defend the plant from being
eaten by animals.
• The stem makes food for the plant. Cactus
and ocotillo are examples of plants with
spines.