Download video slide - CARNES AP BIO | "Nothing in biology makes

Chapter 35
Plant Structure, Growth, and
Development
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview of Plant Structure
•
BOTH genes and the environment affect plant structure
and physiology.
•
Plants have THREE BASIC ORGANS: roots, stems, and
leaves.
•
Plant organs are composed of THREE TISSUE
SYSTEMS: dermal, vascular, and ground.
•
Parenchyma, collenchyma, and sclerenchyma are three
TYPES OF PLANT CELLS
•
The move to land forced development of adaptations –
natural selection.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Three Basic Plant Organs: Roots, Stems, and Leaves
• 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 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Forces of Nature
• Why 2 different systems?
– Soil – provides water and minerals, but no light
present
– Air – source of CO2
• SO, plants developed 2 systems:
– Root systems (subterranean)
– Shoot systems (aerial)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plant Organs: Roots, Stems, and Leaves
• Plant organs are organized into a root system and a
shoot system
Reproductive shoot (flower)
Terminal bud
The root system and the
shoot system are
connected by vascular
tissue (purple strands) that
is continuous throughout
the plant.
Node
Internode
Terminal
bud
Shoot
system
Vegetative
shoot
Leaf
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral roots
Figure 35.2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Root
system
3 Organs of Plants
• Roots –
–
*anchor plant, prevent erosion
–
*absorb minerals and water
–
*store food
• Stems –
–
*transport system
–
*store food (tubers – ex potato)
–
*support leaves
–
*protect tissues
• Leaves –
*photosynthesis
–
*funnel water to roots
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Roots
• 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
Figure 35.3
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Root Types
• Many plants have modified
roots
• Fibrous vs. Taproot
–
Fibrous: mat of thin roots
that spread out below
ground (monocots).
–
Taproot: consists of one
large, vertical root (dicots).
• Root Hairs – provide surface
area for max absorption of
H2O
• Adventitious Roots – roots
that arise above ground from
stems or even from
leaves…help support plant.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Root Structure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Stems and Buds
• A stem is an organ consisting of
– An alternating system of nodes, the points at
which leaves are attached
– Internodes, the stem segments between nodes
• An axillary bud
– Is a structure that has the potential to form a
lateral shoot, or branch
• A terminal bud
– Is located near the shoot tip and causes
elongation of a young shoot
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Many Plants have Modified Stems
(a) Stolons. Shown here on a
strawberry plant, stolons
are horizontal stems that grow
along the surface. These “runners”
enable a plant to reproduce
asexually, as plantlets form at
nodes along each runner.
Storage leaves
Stem
(d) Rhizomes. The edible base
of this ginger plant is an example
of a rhizome, a horizontal stem
that grows just below the surface
or emerges and grows along the
surface.
Node
Root
Figure 35.5a–d
(b) Bulbs. Bulbs are vertical,
underground shoots consisting (c)
Tubers. Tubers, such as these
mostly of the enlarged bases
red potatoes, are enlarged
of leaves that store food. You
ends of rhizomes specialized
can see the many layers of
for storing food. The “eyes”
modified leaves attached
arranged in a spiral pattern
to the short stem by slicing an
around a potato are clusters
onion bulb lengthwise.
of axillary buds that mark
the nodes.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Rhizome
Root
Leaves
• The leaf
– Is the main photosynthetic organ of most
vascular plants
• Leaves generally consist of
– A flattened blade and a stalk
– The petiole, which joins the leaf to a node of
the stem
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Leaf Morphology and Classification of Angiosperms
• In classifying angiosperms taxonomists may
use leaf morphology as a criterion
(a) Simple leaf. A simple leaf
is a single, undivided blade.
Some simple leaves are
deeply lobed, as in an
oak leaf.
Petiole
(b) Compound leaf. In a
compound leaf, the
blade consists of
multiple leaflets.
Notice that a leaflet
has no axillary bud
at its base.
(c) Doubly compound leaf.
In a doubly compound
leaf, each leaflet is
divided into smaller
leaflets.
Figure 35.6a–c
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Axillary bud
Leaflet
Petiole
Axillary bud
Leaflet
Petiole
Axillary bud
Modified Leaves
• Some plant species have evolved modified
leaves that serve various functions
(a) Tendrils. The tendrils by which this
pea plant clings to a support are
modified leaves. After it has “lassoed”
a support, a tendril forms a coil that
brings the plant closer to the support.
Tendrils are typically modified leaves,
but some tendrils are modified stems,
as in grapevines.
(b) Spines. The spines of cacti, such
as this prickly pear, are actually
leaves, and photosynthesis is
carried out mainly by the fleshy
green stems.
(c) Storage leaves. Most succulents,
such as this ice plant, have leaves
modified for storing water.
(d) Bracts. Red parts of the poinsettia
are often mistaken for petals but are
actually modified leaves called bracts
that surround a group of flowers.
Such brightly colored leaves attract
pollinators.
Figure 35.6a–e
(e) Reproductive leaves. The leaves
of some succulents, such as Kalanchoe
daigremontiana, produce adventitious
plantlets, which fall off the leaf and
take root in the soil.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Three Tissue Systems: Dermal, Vascular, and Ground
• Each plant organ has dermal, vascular, and
ground tissues
Vascular – transport
(xylem and phloem)
Dermal – outer coverings,
protection, water conservation
(epidermis, cuticle)
Ground – filler, packing material
for cushioning
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Tissue Systems in Plants
• The dermal tissue system
– Consists of the epidermis and periderm
• The vascular tissue system
– Carries out long-distance transport of materials
between roots and shoots
– Consists of two tissues, xylem and phloem
• Ground tissue
– Includes various cells specialized for functions
such as storage, photosynthesis, and support
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Xylem and Phloem
•
Xylem conveys water and dissolved minerals upward from roots into
the shoots
•
Phloem transports organic nutrients from where they are made to
where they are needed
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Common Types of Plant Cells
• Like any multicellular organism
– A plant is characterized by cellular differentiation, the
specialization of cells in structure and function
• Some of the major types of plant cells include
– Parenchyma
– Collenchyma
– Sclerenchyma
– Water-conducting cells of the xylem
– Sugar-conducting cells of the phloem
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Parenchyma, Collenchyma, and Sclerenchyma Cells
Unspecialized plant
cell that carries most
of the metabolism,
synthesizes and stores
organic products, and
develops into a more
differientiated cell
type.
Flexible plant cell that
occurs in strands or
cylinders that support
young plant parts of
the plant without
restraining growth.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Rigid, supportive plant
cell usually lacking
protoplasts and
possessing thick
secondary walls
strengthened by lignin
at maturity.
Plant Meristems
• Meristems generate cells for new organs
• Apical meristems produce primary growth
– Are located at the tips of roots and in the buds
of shoots
– Elongate shoots and roots through primary
growth
• Lateral meristems produce secondary growth
– Add thickness to woody plants through
secondary growth
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
An Overview of Primary and Secondary Growth
Primary growth in stems
Shoot apical
meristems
(in buds)
Epidermis
Cortex
Primary phloem
In woody plants,
there are lateral
meristems that
add secondary
growth, increasing
the girth of
roots and stems.
Vascular
cambium
Cork
cambium
Primary xylem
Lateral
meristems
Pith
Secondary growth in stems
Apical meristems
add primary growth,
or growth in length.
Pith
Primary
xylem
Root apical
meristems
Figure. 35.10
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Secondary
xylem
Periderm
Cork
cambium
The cork
cambium adds
secondary
dermal tissue.
Cortex
Primary
phloem
The vascular
cambium adds
Secondary
secondary
phloem
xylem and
Vascular cambium
phloem.
Growth in Woody Plants
• Primary and secondary growth occur
simultaneously but in different locations
Terminal bud
Bud scale
Axillary buds
Leaf scar
Node
This year’s growth
(one year old)
Stem
Internode
One-year-old side
branch formed
from axillary bud
near shoot apex
Leaf scar
Last year’s growth
(two years old)
Figure 35.11
Growth of two
years ago (three
years old)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Scars left by terminal
bud scales of previous
winters
Leaf scar
Primary Growth
• Primary growth lengthens roots and shoots
• Primary growth produces the primary plant
body, the parts of the root and shoot systems
produced by apical meristems
• The primary growth of roots
– Produces the epidermis, ground tissue, and
vascular tissue
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Primary Growth of Roots
• The root tip is covered by a root cap, which
protects the delicate apical meristem as the
root pushes through soil during primary growth
Cortex
Vascular cylinder
Epidermis
Key
Root hair
Dermal
Ground
Zone of
maturation
Vascular
Zone of
elongation
Apical
meristem
Root cap
Figure 35.12
100 m
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Zone of cell
division
Primary Growth of Shoots
• A shoot apical meristem
– Is a dome-shaped mass of dividing cells at the
tip of the terminal bud
– Gives rise to a repetition of internodes and
Apical meristem
Leaf primordia
leaf-bearing nodes
Developing
vascular
strand
Axillary bud
meristems
Figure. 35.15
0.25 mm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Secondary Plant Growth
• Secondary growth adds girth to stems and
roots in woody plants
• Secondary growth
– Occurs in stems and roots of woody plants but
rarely in leaves
• The secondary plant body
– Consists of the tissues produced by the
vascular cambium and cork cambium
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Primary and Secondary Growth of a Stem
(a) Primary and secondary growth
in a two-year-old stem
Epidermis
Cortex
Primary
phloem
Vascular
cambium
Primary
xylem
Pith
Periderm
(mainly cork
cambia
and cork)
1 In the youngest part of the stem, you can see the primary
plant body, as formed by the apical meristem during primary
growth. The vascular cambium is beginning to develop.
1
Pith
Primary xylem
Vascular cambium
Primary phloem
Cortex
2
Phloem ray
3
Xylem
ray
Primary
xylem
Secondary xylem
Vascular cambium
Secondary phloem
Primary phloem
4 First cork cambium
2 As primary growth continues to elongate the stem, the portion
of the stem formed earlier the same year has already started
its secondary growth. This portion increases in girth as fusiform
initials of the vascular cambium form secondary xylem to the
inside and secondary phloem to the outside.
Epidermis
3 The ray initials of the vascular cambium give rise to the xylem
and phloem rays.
4 As the diameter of the vascular cambium increases, the
secondary phloem and other tissues external to the cambium
cannot keep pace with the expansion because the cells no
longer divide. As a result, these tissues, including the
epidermis, rupture. A second lateral meristem, the cork
cambium, develops from parenchyma cells in the cortex. The
cork cambium produces cork cells, which replace the epidermis.
5 In year 2 of secondary growth, the vascular cambium adds to
the secondary xylem and phloem, and the cork cambium
produces cork.
Cork
6
6 As the diameter of the stem continues to increase, the
outermost tissues exterior to the cork cambium rupture and
slough off from the stem.
Primary
phloem
Secondary
phloem
Vascular
cambium
Secondary
xylem
Primary xylem
Pith
Figure 35.18a
Secondary
xylem (two
years of
production)
Vascular cambium
Secondary phloem
5 Most recent
cork cambium
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
7 Cork cambium re-forms in progressively deeper layers of the
cortex. When none of the original cortex is left, the cork
cambium develops from parenchyma cells in the
secondary phloem.
8 Each cork cambium and the tissues it produces form a
layer of periderm.
9 Bark consists of all tissues exterior to the vascular
cambium.
8 Layers of
periderm
9 Bark
7 Cork
Anotomy of a Three Year Old Stem
Secondary phloem
Vascular cambium
Cork
cambium
Cork
Secondary Late wood
Early wood
xylem
Periderm
(b) Transverse section
of a three-yearold stem (LM)
Xylem ray
Bark
0.5 mm
Figure 35.18b
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
0.5 mm
Anatomy of a Tree Trunk
Growth ring
Vascular
ray
Heartwood
Secondary
xylem
Sapwood
Vascular cambium
Secondary phloem
Bark
Layers of periderm
Figure 35.20
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cork Cambia and the Production of Periderm
• The cork cambium
– Gives rise to the secondary plant body’s
protective covering, or periderm
• Periderm
– Consists of the cork cambium plus the layers
of cork cells it produces
• Bark
– Consists of all the tissues external to the
vascular cambium, including secondary
phloem and periderm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Growth: Cell Division and Cell Expansion
• Growth, morphogenesis, and differentiation produce the
plant body
• The three developmental processes of growth,
morphogenesis, and cellular differentiation act in concert
to transform the fertilized egg into a plant
• By increasing cell number
– Cell division in meristems increases the potential for
growth
• Cell expansion
– Accounts for the actual increase in plant size
• The plane (direction) and symmetry of cell division
– Are immensely important in determining plant form
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Leaf Anatomy
• The epidermis is covered by a waxy cuticle
made of cutin to minimize water loss. The
cuticle is transparent to allow light to penetrate.
• Guard cells are modified epidermal cells that
contain chloroplasts, are photosynthetic, and
control the opening of stomates.
– Stomata are tiny pores flanked by guard cells –
they allow gas exchange between the leaf and
surrounding air. Guard cell behavior is
controlled by turgor pressure.
– Transpiration is the loss of water through the
stomata of plants.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Leaf Anatomy
• The inner part of the leaf consists of palisade parenchyma and
spongy mesophyll cells whose function is photosynthesis.
–
The cells in the palisade layer are packed tightly, while the spongy
cells are loosely packed to allow for diffusion of gases into and out
of these cells.
• Xylem transport water to leaf tissues. Phloem transports “food”
from leaf tissues to sink cells.
–
In phloem, hydrostatic pressure is generated at one side of a
sieve tube, forcing sap to the opposite end of the tube (a concept
known as bulk flow).
• Vascular bundles or veins are located in the mesophyll and carry
water and nutrients from the soil to the leaves and also carry sugar
from the leaves to the rest of the plant.
• Specialized mesophyll cells called bundle sheath cells surround the
veins and separate them from the rest of the mesophyll.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Leaf Anatomy
Guard
cells
Key
to labels
Dermal
Ground
Stomatal pore
Vascular
Cuticle
Epidermal
cell
Sclerenchyma
fibers
50 µm
(b) Surface view of a spiderwort
(Tradescantia) leaf (LM)
Stoma
Upper
epidermis
Palisade
mesophyll
Bundlesheath
cell
Spongy
mesophyll
Lower
epidermis
Guard
cells
Cuticle
Vein
Xylem
Phloem
(a) Cutaway drawing of leaf tissues
Guard
cells
Figure 35.17a–c
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vein
Air spaces
Guard cells
(c) Transverse section of a lilac 100 µm
(Syringa) leaf (LM)
Leaf Adaptations to Various Environments
• Many leaves have specialized adaptations to
various environments:
– small leaves found on conifers reduce water
loss
– succulents have leaves modified for storing
water
– cacti have spines – modified leaves that
reduce water loss
– C4 and CAM plants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings