Transcript Lecture #13 Date ______

UNIT IX – KINGDOM PLANTAE
• Big Campbell –
Ch 29, 30, 35 – 39
• Baby Campbell –
Ch 17, 31 – 33
KINGDOM PLANTAE
•
All
•
All
•
All
•
All
•
All have cell walls
composed of
•
Most contain
I. EVOLUTION OF PLANTS
•
Evolved from green algae
known as charophytes
•
Land Adaptations
 Obtaining Resources
 Organs
 Vascular tissue in
plants
 Apical meristem
 Support
 Lignin
 Maintaining Moisture
 Cuticle
 Stomata
I. EVOLUTION OF PLANTS, cont
 Reproduction
 Alternation of
Generations
 Walled spores
produced in
sporangia
 Production of
gametes within
multicellular
structures called
gametangia
 Developing embryo
protected, nourished
by female parent
plant
II. PLANT CLASSIFICATION
II. PLANT CLASSIFICATION, cont
Bryophytes
• Non-vascular
• Mosses, liverworts, and
hornworts
• Flagellated (water)
sperm
• No vascular tissue
• No lignin (short stature)
• Haploid gametophyte is
the dominant
generation
II. PLANT CLASSIFICATION, cont
Bryophyte Life Cycle
II. PLANT CLASSIFICATION, cont
Pterophytes
• Seedless vascular plants
• Ferns, club ‘moss’, horsetails
• Contain vascular tissue
– Xylem
– Phloem
• True roots and leaves
• Roots have lignified vascular
tissue
• Dominant stage =
• Bisexual gametophyte
• Flagellated sperm
• Carboniferous period plants
II. PLANT CLASSIFICATION, cont
Fern Life Cycle
II. PLANT CLASSIFICATION, cont
Seed Plants
II. PLANT CLASSIFICATION, cont
Seed Plants
• Gymnosperms & Angiosperms
• Reduced Gametophyte
• Seed
–
–
–
–
• Heterosporous
– Megaspore → female gametophyte → egg
– Microspore → male gametophyte → sperm
• Pollen
II. PLANT CLASSIFICATION, cont
Seed Plants
II. PLANT CLASSIFICATION, cont
Seed Plants
Seed Germination
II. PLANT CLASSIFICATION, cont
Gymnosperms
• Vascular Plants with seeds
• “Naked seed”
 Seed is not protected by a
fruit
• Cone-bearing plants
• Ginkgo, cycads, and
conifers
• “Evergreens”
• Most have needles
• Reproduction occurs in the
cone
II. PLANT CLASSIFICATION, cont
Angiosperms
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•
•
•
Vascular plant with seeds, fruit
“Flowering plants”
Most successful of all plants
Flower - Reproductive system
of angiosperms
• Fruit – Protects, disperses seed
• Angiosperms divided into 2
groups:
 Monocots - 1 embryonic seed leaf
(lilies, palms, grasses, grain
crops)
 Dicots - 2 embryonic seed leaves
(roses, peas, sunflowers, oaks,
maples)
II. PLANT CLASSIFICATION, cont
Angiosperms
Monocot vs. Dicot
II. PLANT CLASSIFICATION, cont
Angiosperms
Flower Structure
• Sepals
 Encloses, protects flower
• Petals
 Attracts pollinators
• Stamen




Male reproductive organ
Anther, filament
Pollen produced by anther
Pollen is male gametophyte
• Carpel (Pistil)




Female reproductive organ
Stigma, style, ovary, ovule
Ovule is female gametophyte
Fertilization occurs in ovule
• Fruit
• Pollination
II. PLANT CLASSIFICATION, cont
Angiosperm Adaptations
 Pollen grain lands on “sticky
stigma”
 Pollen tube formed
 Extends through style to ovary
 Mitosis occurs in pollen grain to
form 2 sperm
• Double Fertilization
 One sperm fertilizes egg
contained in ovule; forms zygote
 Nucleus of second sperm fuses
with diploid cell in embryo sac
 Triploid cell develops into foodstoring tissue called endosperm
A CLOSER LOOK AT PLANT
STRUCTURE & GROWTH
III. PLANT STRUCTURE, cont
Three Tissue Types
•
Dermal
– Outer protective covering
– Made up of a single layer of cells
called the epidermis in nonwoody plants
• Root hairs
• Cuticle
– Woody plants have a tissue layer
called periderm
•
Vascular
– Xylem
• Transports water, minerals
• Two types of “cells”
 Vessel Elements
 Tracheids
– Phloem
• Transports nutrients
• Composed of
 Sieve Tube Members
 Companion Cells
III. PLANT STRUCTURE
•
Ground
– Remaining plant tissue
– Location of photosynthesis, hormone production,
carbohydrate storage, etc
– Made up of three cell types
– Parenchyma
• Most abundant cell type
• Living cells with thin, flexible primary cell walls
• Perform most of the metabolic functions
• Contain large central vacuole
• Capable of cell division, differentiation
– Collenchyma
• Uneven, thickened primary cell walls; lack
secondary cell walls
• Living cells that provide flexible support
– Sclerenchyma
• Provide structural support
• Contain secondary cell walls, strengthened with
lignin
• Dead at maturity
• Two types
– Fibers
– Sclereids
III. PLANT STRUCTURE, cont
A Closer Look at Roots
III. PLANT STRUCTURE, cont
A Closer Look at Stems
• Vascular bundles (xylem and phloem)
• Surrounded by ground tissue (xylem faces pith and phloem faces cortex)
 Mostly parenchyma; some collenchyma, sclerenchyma for support
III. PLANT STRUCTURE, cont
A Closer Look at Leaves
•
Epidermis
 Cuticle
 Stomata & Guard
Cells
•
Mesophyll
 Ground tissue
between upper &
lower epidermis
 Parenchyma cells
 Made up of 2 regions
 Palisade
 Spongy
IV. PLANT GROWTH
• Indeterminate Growth
• Growth carried out through increased
cell numbers and increased cell size
• Meristem
 Embryonic tissue capable of unlimited
growth; growing part of plant
 Two types
Apical Meristem
– Found at tips
– Known as primary growth
Lateral Meristem
– Cylinders of cells that extend
the length of the plant
– Increases girth of plant
– Known as secondary growth
IV. PLANT GROWTH, cont
Primary Growth
The Root System
• Provides plant with water, minerals;
anchors plant
• Root Cap
 Protects the apical meristem; cells
constantly replaced by meristem
• Zone of Cellular Division
 Apical meristem
• Zone of Cellular Elongation
 Made up of cells increasing in
length
• Zone of Cellular Maturation
 Differentiation of cells to make up
three tissue types
• Root Hairs
•
•
IV. PLANT GROWTH, cont
Secondary Growth
Increases girth of plant
Carried out by two cylinders of cells
that run the length of root, stem
known as lateral meristems
 Vascular Cambium – Found
only in woody gymnosperms,
angiosperms. Occurs between
1˚ xylem & phloem. Inside
vascular cambium → secondary
xylem; outside → secondary
phloem.
 Secondary xylem makes up
the wood of a tree. Cells
contain large amounts of
lignin. Layering of 2˚ xylem =
growth rings.
 Secondary phloem
transports sugar; part of bark
IV. PLANT GROWTH, cont
Secondary Growth, cont
 Cork Cambium
 Typically produces new cells
to the outside
 Produces cork cells; replace
epidermis as it is sloughed
off.
 Forms from parenchyma
cells.
 Important component of
bark, although bark
technically consists of all
cells outside vascular
cambium
 Heartwood
 Sapwood
Plant Nutrition
V. WATER TRANSPORT
• Water Transport
 Osmosis
 Hyper, Hypo, Iso
• Water moves from high to low water
potential
 Ψ = Ψs + Ψp
 Solute potential of pure water = 0
 Solute present; solute potential is
negative
 Pressure potential increased by cell wall
• Plasmolysis
 Cell in hypertonic environment
 Cell membrane pulls away
• Turgor pressure
 Cell in hypotonic environment
 Influx of water
V. WATER TRANSPORT, cont
Uptake of Water & Minerals
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•
•
Root hairs greatly increase surface area,
absorptive capacity
Water and solutes enter through epidermis
and cortex of root
Movement into xylem can happen in 2 ways:
 Symplastic – Water & solutes cross cell
wall, cell membrane into epidermal cell.
Plasmodesmata allow solution to move
from cell to cell without crossing cell
membranes all the way to xylem
 Apoplastic – Solution does not move
into epidermal cells; stays in extracellular
spaces. Crosses no cell membranes
until it reaches Casparian strip – a
continuous waxy barrier that forces
solution through selectively permeable
cell membrane of endodermal cell, then
enters xylem.
V. WATER TRANSPORT, cont
Uptake of Water & Minerals
A Closer Look
V. WATER TRANSPORT, cont
Transport of Xylem Sap From Roots to Shoots
• Transpiration
 Loss of water vapor from
leaves pulls water from
roots (transpirational pull)
 Cohesion and adhesion of
water
• Root pressure
 At night, low transpiration,
roots cells continue to
pump minerals into xylem
 Generates pressure,
pushing sap upwards;
guttation
 Not as great a force as
transpiration
V. WATER TRANSPORT, cont
Control of Transpiration
• Photosynthesis-Transpiration compromise….
• Guard cells control the size of the stomata
• Xerophytes - Plants adapted to arid environments; have thick cuticle,
small spines for leaves
• CAM, C4 plants
VI. NUTRIENT TRANSPORT
Essential Nutrients Required by Plants
• Macro







Carbon
Oxygen
Hydrogen
Nitrogen
Phosphorus
Sulfur
Potassium, calcium,
magnesium
• Micro
 cofactors of enzymes
 chlorine, iron, boron,
manganese, zinc, copper,
molybdenum, nickel
VI. NUTRIENT TRANSPORT, cont
Phloem Cells
VI. NUTRIENT TRANSPORT, cont
Transport of Phloem Sap
• Sugar Source – Plant organ that
produces sugar; leaves
• Sugar Sink – Organ that consumes or
stores sugar; growing roots, stems, fruit
• Translocation – Process of sugar
transport
 Sugar is actively transported into phloem
tube
 Raises solute concentration; lowers ψ
 Water moves into phloem tube;
increases pressure at the source end
 Forces sap to move toward area of lower
pressure
 Pressure gradient by movement of sugar
out of phloem tube at sink end
 Xylem moves water from sink to source
VII. PLANT RELATIONSHIPS
• Mutualism
 Rhizobium bacteria
 Nitrogen fixation
 Found in roots of legume (bean) plants
 Mycorrhizae fungi
 Increase plant root surface area
• Parasitism
 Mistletoe
• Epiphytes
 Live attached to plant but
nutritionally self-supportive
 Orchids
• Carnivorous
 Venus Flytrap
 Pitcher Plants
 Insects provide needed minerals
Control Systems in Plants
VIII. TROPISM
• Movement toward or away from a
stimulus
 Phototropism
 Adaptive response first
tested by Darwin
 Went identified chemical
responsible
 Auxin
Acts by stimulating
growth
 Gravitropism
 Thigmatropism
IX. PLANT HORMONES
• Chemical signals that coordinate activities of an organism
• Produced in one part of the body and then transported to other parts
of the body
• Bind to specific receptor; triggers a signal transduction pathway
• Low concentrations; have a profound effect
• Five major types of plant hormones
 Auxins
 Cytokinins
 Giberellins
 Abscisic Acid
 Ethylene
IX. PLANT HORMONES, cont
Auxin
• IAA (indoleacetic acid)
• Found in seed embryo,
meristems of apical
buds and young leaves
• Stimulates elongation
of cells
• Functions include stem
elongation, root
growth, differentiation,
branching, fruit
development; apical
dominance; tropisms
• Produced by
developing seeds
IX. PLANT HORMONES, cont
Cytokinins
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•
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•
Promote cell division, cytokinesis
Found in roots, actively growing tissues
Stimulate root growth and differentiation, germination
Slow down aging of flowers, leaves
Work with auxins to control apical dominance; that is, the ability of the
terminal bud to suppress the growth of axillary buds
IX. PLANT HORMONES, cont
Gibberellins
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•
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•
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Isolated by Japanese farmers; originally thought it was due to a fungus
Acts as growth regulator
Stimulate cell division and elongation in stems and leaves
Enhance effects of auxins
Found in roots and young leaves
IX. PLANT HORMONES, cont
Abscisic Acid
• ABA
• Inhibits growth; maintains seed dormancy; causes stomata to close
during dry conditions
• Found in leaves, stems, roots, unripe fruit
IX. PLANT HORMONES, cont
Ethylene
• Gaseous hormone
• Stimulates fruit ripening
 Breaks down cell walls,
“softens” fruit
 Triggers breakdown of
starch to glucose
• Separates leaf from stem;
autumn leaf drop
 Stimulates formation of
an abscission layer
 Works in opposition to
auxins
X. PLANT RESPONSES
• Critical night length controls
flowering
• Short-day Plant
 Light period shorter than a
critical length to flower
 Flower in late summer, fall,
winter
 Poinsettias, chrysanthemums
• Long-day Plant
 Light period longer than a critical
period to flower
 Flower in late spring, early
summer
 Spinach, iris, radish, lettuce
• Day-neutral Plant
 Unaffected by photoperiod
 Tomatoes, rice (is nice!),
dandelions
X. PLANT RESPONSES, cont
Photoperiodism
• Internal plant clock
• Based on relative lengths of day
and night, especially night
• Allows plants to respond to
seasonal changes
• Phytochromes
 Plant pigment that measures length
of darkness in a photoperiod
 Absorbs red light; therefore, appear
bluish in color
 Two forms
 Pr – “red-absorbing”,
660 nm
 Pfr - “far-red absorbing”, 730
nm