Plant Anatomy

1
Plant Anatomy

• Plant Structure
• Plant Morphology deals with the external
  structure of plants
• Plant Anatomy deals with the internal structure

2
Plant Anatomy is Embedded into the fabric of the
Discipline of Botany
Anatomy is the study of how cells and tissues are
organized in plants
Anatomy
3
Plant Physiology
Physiology
Anatomy
How form relates to function.
4
Genetics/Ontogeny
How genetic information is expressed in plant
structure.
How the expression of genetic information timed
to generate a coherent organism.
How the expression of genetic information is
influenced by the environment.
Physiology
Genetics ontogeny
Anatomy
5
Phylogeny/Evolution
What structures are analogous?
What structures are homologous?
What does this tell us about the tree of life?
Physiology
Genetics ontogeny
Anatomy
Phylogeny Evolution
6
Ecology
How does structure/function relate to what a
where a plant lives, and what a plant does in
ecosystems?
Physiology
Genetics ontogeny
Anatomy
Ecology
Phylogeny Evolution
7
Plant Anatomy is Embedded into the fabric of the
Discipline of Botany
Physiology
Genetics ontogeny
Anatomy
Ecology
Phylogeny Evolution
8
Plant Cells and Tissuesan Evolutionary
Perspective
9
Plants Are Structurally Complex
All the cells of a plant are genetically
identical, but the information is expressed in
different ways in different places in a
synchronized fashion.
10
Plants Arose from the Green Algae During the
Silurian Period Over 400 Million Yeas Ago
11
Evidence That Plants Arose from the Green Algae

• Pigmentation

• Cellulose in their cell walls

• Starch stored in the plastid

• Some green algae undergo cell division by means
  of a phragmoplast

12
Plants are More Structurally Complex than Any of
the Green Algae
13
Plants Have Become Structurally Complex in
Response to the Challenges of Life on Land
14
and plants can be considered simply as
group of the green algae that have become
adapted to life on land.
Sequoiadendron
15
Solutions to Challenges of Life on Land
Dehydration
--------------------gt Dermal tissue
--------------------gt Secondary Walls
Support
Transport of Water and Minerals
--------------------gt Xylem Tissue
Transport of Photosynthate
--------------------gt Phloem Tissue
Syngamy
--------------------gt To be considered later
16
Vascular plants are made up of three tissue
systems which are represented in each plant
organ.
17
Ground Tissue System
Includes cells and tissues like those found in
the green algae
18
Dermal Tissue System
Is an adaptation for water conservation found in
plants
Dermal tissue of a hornwort a non-vascular
plant
19
Vascular Tissue System
Consists of tissues that transport substances in
higher plants
20
Cell Types of the Ground Tissue System
Parenchyma Tissue Composed of Parenchyma Cells
Function
Growth/Wound Healing/Regeneration
Photosynthesis
Storage
Collenchyma Tissue Composed of Collenchyma Cells
Function
Support
21
Cell Types of the Ground Tissue System
cont.Sclerenchyma
Sclerenchyma (hard) cells develop a secondary
wall and serve to support and protect the plant.
Sclerenchyma is found in all three tissue
systems. You will observe two types of
sclerenchyma cells in lab
Stone cells
Fibers
22
Cell Types of the Dermal Tissue System
Epidermis
Basal epidermal cells excrete a cuticle - this
keeps water in..and prevents gas exchange
To survive the epidermis must be pierced with
pores. In most plants, guard cells regulate gas
exchange through these pores. Pores regulated by
guard cells are stomata
Trichomes are hairs associated with the epidermis
Root hairs - these form from epidermal cells.
23
Cell Types of the Dermal Tissue System cont.
In woody plants the role of the epidermis is
taken over by a periderm that produces cork.
24
Vascular tissue is necessary for a plant to
become tall.
25
Vascular plants have cells with secondary walls
that include lignin
26
But why not simply remain prostrate?
27
Because of competition for light.
28
The vascular tissue system includes two types of
tissues .
Phloem
Xylem
29
Vascular Tissue System
Xylem Moves water and minerals up the plant
and provides support to the plant.
30
Vascular Tissue System
Phloem Moves photosynthate (usually sucrose)
around the plant
31
Kelps are an example of another photo-autotrophic
group that has become large
32
Kelps are supported by water and have no need for
a tissue like xylem or cells with secondary walls
The kelp Macrocyctis
33
But the lower portion of the plant becomes shaded
The kelp Macrocyctis
34
And kelps have independently evolved a type of
phloem tissue
35
The cells of kelp phloem and plant phloem are
similar, but evolved independently in both
lineages. This is an example of convergent
evolution
36
Xylem is a complex tissue that always includes
tracheary elements
Tracheid
Vessel Element
37
Tracheary elements are dead at maturity and have
a secondary wall
Water moves through these cells by mass flow
The water is under tension and tend to collapse
38
Air pressure can only lift a column of water
about 32 feet and yet plants grow much taller
39
Cohesion-Tension Theory
Text pages 754 - 758
Water is pulled up the tracheary elements,
because water molecules stick together (cohere)
via hydrogen bonds
.
40
Secondary walls keep the tracheary elements from
collapsing
Vessel elements in an elongating plant stem
41
Secondary walls also help support the plant
Vessel element with a complete secondary wall
42
All tracheary elements have pits
Red secondary wall
Black primary wall
43
Tracheids only have pits
44
We will consider the structure of tracheids in
our lab on the gymnosperms
45
A vessel element is a tracheary element with a
perforation plate
46
A perforation is an area between tracheary
elements where both the primary and secondary
wall is absent
47
Vessel elements together from a vessel
48
Vessels have independently evolved in six
different plant groups. You should know that
Flowering plants have them
Conifers dont
The examples of xylem we will see in the lab all
have vessels
49
Phloem is a complex tissue that includes sieve
elements
Sieve Cells (Conifers)
Sieve-Tube Elements (Angiosperms)
50
Sieve Elements Serve as a Conduit for the
Movement of Photosynthate
This movement is based on a pressure gradient
generated osmotically. To generate this gradient
sugar must be loaded at the source and unloaded
at the sink. Living membranes are necessary both
to control the movement of sucrose and for the
osmotic movement of the water into and out of
the Sieve tubes.
Read phloem transport in the text pp. 766 -769.
51
Sieve elements are greatly reduced.They lose
their vacuole, nucleus, and most of the rest of
their cellular structure as they mature.
Adjacent sieve elements are interconnected by
clusters of pores through which materials flow
from one element to another.
52
Sieve-tube members are one type of sieve element.
They are found only in the flowering plants.
53
Sieve-Tube Members Have Sieve Plates
54
Sieve-Tube Members are Associated with Companion
Cells
55
Gymnosperms have a different type of sieve
element called a sieve cell
56
Associated with albuminous cells
57
Vascular Tissue System
Xylem
Always includes tracheary elements
Tracheids and/or vessel elements
May have
Parenchyma
Fibers
Other types we will not consider
58
Vascular Tissue System
Phloem
Always has sieve elements
If sieve-tube members, then also companion cells
If sieve cells, then also albuminous cells
Some plants have sieve elements that are
neither. In these cases the cells are simply
called sieve elements
May also have
Parenchyma cells
Fibers
59
Primary Tissues
Are derived from apical meristems composed of
parenchyma cells
60
In lab, note how these three tissue systems are
organized in each of the three plant organs
formed by primary growth.
61
(No Transcript)
62
Secondary Tissues are Derived from Lateral
Meristems Called Cambia
63
Except for the pith and some primary xylem
bordering the pith, this is all secondary tissue
64
The Vascular Cambium Produces Xylem to the Inside
and Phloem to the Outside
65
The Cork Cambium Produces Dermal Tissue (cork)
to the Outside
66
(No Transcript)
67
Secondary Growth Results in Additions to the
Vascular Tissue and Dermal Tissue Systems, but
not to the Ground Tissue System