Download Growth! Plant systems Plant systems

Growth!
The plant cell—tissue systems,
tissues, and cells
1. 
2. 
3. 
4. 
5. 
Review of the plant body
The three tissue systems
Tissues that make up the tissue systems
Cell types that make up the tissues
Components of a cell
Figure 35.2 Morphology of a flowering plant: an overview
Plant systems
•  The plant body has a hierarchy of organs,
tissues, and cells, like multicellular animals
–  Have organs composed of different tissues, which are
in turn composed of cells
•  The basic morphology of vascular plants
–  Reflects their evolutionary history as terrestrial
organisms that draw nutrients from two very different
environments: below-ground and above-ground
•  Three basic
organs
evolved: roots,
stems, and
leaves
•  They are
organized into
a root
system and a
shoot system
Figure 35.2 Morphology of a flowering plant: an overview
Plant systems
•  The plant body has a hierarchy of organs, tissues, and
cells, like multicellular animals
–  Have organs composed of different tissues, which are in turn
composed of cells
•  The basic morphology of vascular plants
–  Reflects their evolutionary history as terrestrial organisms that
draw nutrients from two very different environments: belowground and above-ground
•  Three basic
organs
evolved: roots,
stems, and
leaves
•  They are
organized into
a root
system and a
shoot system
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Roots
Roots cont.
•  A root
–  Is an organ that anchors the vascular plant
–  Absorbs minerals and water
–  Often stores organic nutrients
•  In most plants
–  The absorption of water and
minerals occurs near the root
tips, where vast numbers of
tiny root hairs increase the
surface area of the root
Many plants have modified roots
(a) Prop roots
(d) Buttress roots
(b) Storage roots
(c) “Strangling” aerial
roots
•  Gymnosperms and eudicots: taproots with
lateral roots
•  Seedless vascular and monocots: fibrous
root system: spread out
•  Many plants have modified roots:
adventitious roots arise above ground from
stems and even leaves
Stems (shoot system)
•  Nodes: point of leaf attachment
•  Internodes: segments between nodes
•  Axillary buds can form new shoots or
branches
•  Terminal buds can lead to apical
dominance (grow up!)
(e) Pneumatophores
Figure 35.4 Modified shoots: Stolons, strawberry (top left); rhizomes, iris (top
right); tubers, potato (bottom left); bulb, onion (bottom right)
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Figure 35.5 Simple versus compound leaves
Leaves
•  Main photosynthetic organ - but in many,
the stems can dominate too.
•  Blade and petiole (monocots don’t have
petioles - base of the leaf forms a sheath
around leaf.
•  Leaf types:
Figure 35.6 Modified leaves: Tendrils, pea plant (top left); spines, cacti (top
right); succulent (bottom left); brightly-colored leaves, poinsettia (bottom right)
Figure 35.19 Leaf anatomy
Note: “Cuticle” = waxy or fatty layer on
outer wall of epidermal cells
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Leaf types
The plant cell—tissue systems,
tissues, and cells
1. 
2. 
3. 
4. 
5. 
Review of the plant body
The three tissue systems
Tissues that make up the tissue systems
Cell types that make up the tissues
Components of a cell
Figure 35.7 The three tissue systems
The plant cell—tissue systems,
tissues, and cells
1. 
2. 
3. 
4. 
5. 
Figure 35.7 The three tissue systems
Tissue
Systems
Tissues
Ground
Parenchyma
Collenchyma
Sclerenchyma
Vascular
Xylem
Review of the plant body
The three tissue systems
Tissues that make up the tissue systems
Cell types that make up the tissues
Components of a cell
Figure 35.18 Primary tissues, and their functions, in young stems
Sclerenchyma tissue: support of
mature plant parts
Xylem tissue: water & mineral
transport; Phloem tissue:
“food” (sugar) transport
(a.k.a. “pith ray”)
Collenchyma tissue: support of
young, growing parts
Parenchyma tissue:
photosynthesis, storage, and/or
secretion
Phloem
The three tissue systems
Dermal
Epidermis
Epidermal tissue: protection,
control of water loss, and a variety
of other functions
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Figure 35.16 Organization of primary tissues in young stems. Note difference
from root: vascular tissue is arranged in bundles, with ground tissue in center.
Also note difference in arrangement of bundles between dicot and monocot.
Figure 35.15 Organization of tissue systems and tissues in young roots
“Epidermis:” Dermal system, epidermal
tissue
“Cortex:” Ground system, parenchyma
tissue
“Stele:” Vascular system, xylem & phloem
tissues
Figure 35.13 Organization of primary tissues in young roots. Note the
difference between the monocot and the dicot in the arrangement of the xylem
& phloem in the stele.
The plant cell—tissue systems,
tissues, and cells
1. 
2. 
3. 
4. 
5. 
Tissue Systems
Tissues
(& cell types)
Ground
Parenchyma
(parenchyma cells, transfer cells)
Collenchyma
(collenchyma cells)
Sclerenchyma
(fibers & sclereids)
Vascular
Xylem
(tracheids or vessel members, also some
parenchyma cells, fibers, & sclereids )
Phloem
(sieve cells or sieve-tube members, also specialized
parenchyma cells called companion or albuminous
cells, some fibers & sclereids)
Dermal
Epidermis
(ground cells, guard cells, trichomes, and others,
also some fibers & sclereids)
Review of the plant body
The three tissue systems
Tissues that make up the tissue systems
Cell types that make up the tissues
Components of a cell
Three tissue systems of plants
•  Dermal tissue - outer protective covering
–  Epidermis/periderm analogous to skin
–  Cuticle - waxy coating to preserve water
•  Vascular tissue - transport system
–  Xylem: carries water and nutrients from roots to
leaves. Support and food storage too.
–  Phloem: transport organic nutrients (sugar),
amino acids, lipids, hormones etc.
•  Ground tissue - “everything else”.
–  Pith (internal to vascular), Cortex
–  Function in storage, photosynthesis, & support
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Figure 35.8 The three tissue systems of a plant
Plant Cell Types
•  Epidermis
Dermal Tissue
–  Guard Cells
–  Trichomes (appendages). Can be on roots
(facilitate absorption), or on ‘hairy’ leaves reduce solar radiation in xerophytes). Some
secrete salts (in halophiles)
•  These cells provide mechanical protection
•  Many are covered with a cuticle (cutin and
wax) to minimize water loss
Figure 35.8 The three tissue systems of a plant
Plant Cell Types
•  Epidermis
Ground Tissue
–  Guard Cells
•  Ground tissue
pith
cortex
Parenchyma cells
•  Alive at maturity
•  No secondary walls
•  Site of most plant metabolism
•  Play a role in wound healing and
regeneration
–  Parenchyma: photosynthesis and metabolism
(storage and secretion ).
–  Collenchyma: support (flexible)
–  Sclerenchyma: storage, support (firm),
protection
Collenchyma cells
•  Living at maturity
•  No secondary cell walls or lignin
•  Provide flexible support to growing
parts of plant
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Figure 35.8 The three tissue systems of a plant
Sclerenchyma cells
Vascular Tissue
•  Thick secondary walls, usually with lignin
•  Usually dead at maturity
•  Usually specialized for support and strengthening of
parts that have ceased elongating.
–  Sclereids impart hardness to seed coats, shells of
nuts (give pears their grit)
–  Fibers are usually long, slender, tapered (hemp and
flax fibers)
Plant Cell Types
•  Epidermis
–  Guard Cells
•  Ground tissue
–  Parenchyma: photosynthesis and metabolism
–  Collenchyma: support
–  Scelerenchyma: support, storage, protection
•  Vascular tissues
–  Xylem: water and nutrients from roots. Also
support and food storage
•  Tracheids, vessel elements
–  Phloem: sugars from leaves
•  Sieve-tube members, companion cells
Xylem cells
•  Dead at maturity
•  Tracheids found in all vascular plants
–  Long and thin with tapered ends
–  Lignin for structural support
–  Less specialized than vessel elements (‘safer’ though)
•  Vessel elements found mainly in angiosperms
(flowering plants)
–  Generally wider, shorter, and less tapered than
tracheids
–  Has perforations for more efficient water flow - but
perforations are open systems and can be less safe.
Figure 35.8 Water-conducting cells of xylem tissue
Phloem
• Primary and secondary phloem.
Primary phloem is often destroyed
during elongation of the organ.
• Principal conducting cells are the
sieve elements (‘with pores’)
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Figure 35.9 Food-conducting cells of the phloem tissue
Sieve-tube members
•  Alive at maturity, but…
•  Lack nucleus, ribosomes, organelles
(highly specialized like human red
blood cells!)
•  Served by nucleus etc. of adjacent
companion cells
– Connected via plasmodesmata
Figure 35.19 Leaf anatomy
Note: “Cuticle” = waxy or fatty layer on
outer wall of epidermal cells
Plant Growth
1.  Meristems and overview of plant growth
2.  Apical meristems and primary growth
3.  Lateral meristems and secondary growth
Remember: A major
adaptation of land
plants is the meristem
—a region of
perpetual cell division
that allows the plant
to grow rapidly
Figure 35.10 Locations of major meristems
Figure 35.11 Illustration of primary and secondary growth: Morphology of a
winter twig
There are two types of
meristems: Apical and
lateral.
Apical meristems
lengthen the plant
(“primary growth”).
Lateral meristems
thicken the plant with
bark and wood
(“secondary growth”).
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Plant Growth
Figure 35.12 Primary growth of a root. Notice that the apical meristem
produces three primary meristems, which produce the three primary tissue
systems (dermal, ground, and vascular).
1.  Meristems and overview of plant growth
2.  Apical meristems and primary growth
3.  Lateral meristems and secondary growth
Figure 35.13 Organization of primary tissues in young roots. Note the
difference between the monocot and the dicot in the arrangement of the xylem
& phloem in the stele.
Figure 35.14 The formation of lateral roots. Lateral roots arise from the
pericycle—the outermost cell layer of the stele.
Figure 35.12 Primary growth of a root. Notice that the apical meristem
produces three primary meristems, which produce the three primary tissue
systems (dermal, ground, and vascular).
Figure 35.15 The terminal bud and primary growth of a shoot. Just like in the
root, the apical meristem produces three primary meristems, which develop
into the three tissue systems.
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Figure 35.16 Organization of primary tissues in young stems. Note difference
from root: vascular tissue is arranged in bundles, with ground tissue in center.
Also note difference in arrangement of bundles between dicot and monocot.
Plant Growth
1.  Meristems and overview of plant growth
2.  Apical meristems and primary growth
3.  Lateral meristems and secondary
growth
Figure 35.10 Locations of major meristems
Remember:
Secondary growth
happens at the 2
lateral meristems
The interior lateral
meristem, called the
vascular cambium,
produces secondary
xylem (to the interior)
and phloem (to the
exterior).
Figure 35.18 Secondary growth of a stem (Layer 1)
Vascular cambium:
Fusiform initials make cells
elongated vertically, form
secondary xylem (to inside) and
secondary phloem (to the outside)
Ray initials make cells elongated
horizontally-transfer water and
nutrients, store starch
The exterior lateral
meristem, called the
cork cambium,
produces cork cells to
the exterior.
Figure 35.18 Secondary growth of a stem (Layer 2)
Figure 35.18 Secondary growth of a stem (Layer 3)
Cork cambium: meristem for tough
thick covering - replaces epidermis.
Forms from cortex to fill in gaps as
epidermis is stretched and broken
by lateral expansion of stem
Rays maintain connectivity
between secondary xylem and
secondary phloem, allow exchange
of nutrients and water, store starch
and organic nutrients
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Anatomy of a three-year-old stem. How can you tell the stem is 3 years old?
Secondary growth of a stem. How many years old is it?
Notes:
“Wood” = secondary xylem, or
everything on the interior side of the
vascular cambium
“Bark” = everything exterior of the
vascular cambium, including the
secondary phloem and the periderm
(cork cambium + cork)
Also remember: Secondary growth
happens in roots too.
Figure 35.20 Anatomy of a tree trunk
A summary of primary and secondary growth in a woody stem
Oldest xyelm
nonfuctional
Oldest phloem
sloughed off
Oldest xyelm
nonfuctional
Oldest phloem
sloughed off
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