The plant body has a hierarchy of organs, tissues, and cells •Plants ...

Chapter 35-Plant Structure, Growth and Development
Goals for today’s lecture:
General structure of the plant body
Understand three basic plant organs: 1) roots 2) stems 3) leaves
Understand three tissue systems: 1) dermal 2) vascular 3) ground
Differentiate between primary and secondary growth
Differentiate between complex and simple tissues
Understand the different types of plant cells that make up plant tissues
The plant body has a hierarchy of organs, tissues, and cells
•Plants, like multicellular animals, have organs
composed of different tissues, which are in turn are
composed of cells
Three basic organs evolved:
Roots
•Functions of roots:
Leaf
Reproductive shoot (flower)
Terminal bud
Node
Internode
Terminal
bud
Vegetable
shoot
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral roots
Shoot
system
Root
system
•In most plants, absorption of water and minerals
occurs near the root tips, where vast numbers of tiny
root hairs increase the surface area

Stems
•A stem is an organ consisting of
Nodes – the region of the stem from
which 1 or more leaves or
branches emerge
Internode – the stem regions between
the nodes
•Many plants have modified stems
Leaves
•The leaf is the main photosynthetic organ of
most vascular plants
•Leaves generally consist of
•Monocots and eudicots differ in the arrangement of
veins, the vascular tissue of leaves

•Some plant species have evolved modified leaves that serve various functions
Plant bodies are composed of organs, tissues, and cells
Growth
All plants have growth points for shoot and root
tips called apical meristems.
•Apical meristems elongate shoots and roots, a process called primary growth
Shoot apical meristems
Root apical meristems

Apical meristems of most plants generate 3 types of tissue systems:
These tissue systems develop from precursor tissues:
protoderm
Dermal
tissue
Ground
tissue
Vascular
tissue
In nonwoody plants, the dermal tissue system consists of the epidermis
In woody plants, protective tissues called periderm replace the
epidermis in older regions of stems and roots
procambium
The vascular tissue system carries out long-distance transport of
materials between roots and shoots
The two vascular tissues are xylem and phloem
xylem
phloem
ground meristem
Secondary meristems produce wood and bark
Trees, shrubs, and woody vines have 2 additional meristems:

Shoot apical
meristems
(in buds)
Primary growth in stems
Epidermis
Cortex
Primary phloem
Vascular
cambium
Cork
cambium
Lateral
meristems
Pith
Pith
Secondary growth in stems
Primary xylem
Periderm
Cork
cambium
Primary
xylem
Cortex
Primary
phloem
Root apical
meristems
Secondary
xylem
Secondary
phloem
Vascular cambium
Secondary growth
The vascular cambium produces lignin-rich secondary xylem tissue to the inside (wood) and secondary phloem to the
outside (inner bark).
•As a tree or woody shrub ages, the older layers of
secondary xylem, the heartwood, no longer
transport water and minerals
•The outer layers, known as sapwood, still
transport materials through the xylem
Secondary
xylem
Secondary phloem
Vascular cambium
Late wood
Early wood
Cork
cambium
Cork
Periderm
Xylem ray
Bark
Transverse section
of a three-yearold
Tilia (linden)
stem (LM)
0.5 mm
0.5 mm

Plant tissues may be described in two types:
Simple tissues
The normal metabolic cells of the plant, performing
such tasks as photosynthesis, respiration, and
storage.
2) Complex tissues,
These tissues make up the plant’s vascular system and outer coating.
There are three types of simple tissues:
1)Parenchyma tissue
Pith from impatiens stem.
Pine leaf cells.
Parenchyma cells have many different shapes.
2) Collenchyma tissue
3) Sclerenchyma tissue
Collenchyma cells are commonly
found in bundles in the young shoot or
in leaves.
-due to very thick, lignified secondary cell walls.
There are two types of cells found in sclerenchyma, fibers and sclereids.
This image shows a bundle of
sclerenchyma fibers in cross
section.
Fibers
-elongate cells with tapered ends
sclereids
-angular cells that may occur in aggregates or
singly.

Complex tissues are those tissues that are made up of multiple cell types.
Complex tissues make up the specialized tissues of vascular plants.
The vascular system includes the most distinctive of the
complex tissues.
The two major types of tissues in the vascular system are
xylem and phloem.
SUGAR-CONDUCTING CELLS OF THE PHLOEM
WATER-CONDUCTING CELLS OF THE XYLEM
Sieve-tube members:
longitudinal view
(LM)
Vessel Tracheids
100 µm
Companion
cell
Sieve-tube
member
Plasmodesma
Sieve-tube members:
longitudinal view
Sieve
plate
Nucleus
Cytoplasm
Companion
cell
Sieve plate with pores (LM)
30 µm
15 µm
Tracheids and vessels
(colorized SEM)
Vessel elements with
perforated end walls
Vessel
element
Pits
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM

Study outline-Chapter 35-Plant Structure, Growth and Development
Reproductive shoot (flower)
Terminal bud
Know general terminology of the plant body (See Fig.)
Understand structure and function of the three basic organs in the plant..
1) roots 2) stem 3) leaves
(Study figures and images from book and know terminology).
Understand structure and function of the three tissue systems in plants.
1) dermal 2) vascular 3) ground tissue
(Study figures and images from book and know terminology)
Node
Internode
Terminal
bud
Vegetable
shoot
Blade
Leaf
Petiole
Axillary
bud
Stem
Taproot
Lateral roots
Shoot
system
Root
system
Understand the function of an apical meristem.
Understand the difference between primary growth and secondary growth in plants.
Be able to differentiate between tissue systems, tissues (simple and complex), and different types of cells.
protoderm, procambium, and ground meristem
Simple tissues-parenchyma, collenchyma, and sclerenchyma- What type of cells are they composed of?
What is the function of each?
Complex tissues-xylem and phloerm-What type of cells are they composed of?
What is the function of each?
precursor tissues that give rise to epidermis, vascular tissue, and
ground tissue