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Botany
(the Study of Plants)
General Plant Review
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All plants are:
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Eukaryotic
Autotrophic
Multicellular
Cell Walls with cellulose
Chloroplasts w/ chlorophyll
a, b, and carotenoids
May have waxy cuticle to
prevent water loss.
Stomata allow gas
exchange.
Plants probably evolved
from green algae
(charophytes)
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Chloroplast similarity
Biochemical similarities
Cell Wall similarities
Plant Reproduction
Alternation of Generations – plants grow a separate,
haploid organism to produce gametes; the same plant
exists in two different forms during its life, although
sometimes it’s hard to differentiate between the forms
Multicellular
Sporophyte – (2N)
Mitosis
Meiosis
Zygote (2N)
fertilization
Unicellular
Gametes (egg
& sperm)
Multicellular
Gametophyte (N)
Unicellular
Spores (N)
Evolutionary Trend – early plants displayed the gametophyte
(n) as the dominant structure, modern plants show the
sporophyte as dominant (2n) (Ex: Moss is HAPLOID, but Oak
Trees are DIPLOID)
zygote
GREEN ALGA
BRYOPHYTE
FERN
GYMNOSPERM
ANGIOSPERM
Classifying Plants

Plants can be divided into 2 major categories based
on their characteristics:
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Nonvascular Plants
 Do NOT have specialized tissues to transport water and
nutrients
 Instead, these plants transport water from cell-to-cell by
osmosis
Vascular Plants
 Have specialized tissues to transport water and nutrients in
plants
 Xylem – carries water upward from roots
 Phloem – carries nutrients and carbohydrates produced by
photosynthesis
Nonvascular Plants (Bryophytes)
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Short with no specialized tissues to transport water
Major types:
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Mosses
Liverworts
Hornworts
Nonvascular Plants/
Bryophytes
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Mosses
 Have rhizoids that anchor
them to the ground
(instead of roots)
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Depend on water for
fertilization
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The sperm must swim to the
egg
Therefore, nonvascular
plants must live in MOIST
environments
Gametophyte is the dominant
phase of the life cycle
Moss/ Bryophyte Life Cycle
zygote
Zygote grows,
develops into a
sporophyte while
still attached to
gametophyte.
mature
sporophyte
Diploid Stage
Fertilization
Haploid Stage
Meiosis
Spores
germinate.
spermproducing
structure
eggproducing
structure
male
gametophyte
female
gametophyte
Vascular Plants/Tracheophytes
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Have specialized tissues to transport water
and nutrients in plants called Xylem & phloem
Vascular plants (tracheophytes) can be
divided into 2 categories:
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Seedless vascular plants (spores)
Seed (vascular) plants
Seedless Vascular Plants
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Ferns – A Close Up
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Diploid sporophyte is the
dominant stage
Have rhizomes, which are
underground stems
Fronds: large “leaves”
where spores develop
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Develop spores in
sporangia on underside
of fronds
Reproduce using spores
A sorus (plural: sori) is a
cluster of sporangia
Fern Life Cycle
Sporophyte still attached
to gametophyte
sorus
zygote
fertilization
egg
rhizome
Diploid Stage
meiosis
Haploid Stage
Spores develop
Spores
are
released
sperm
mature
gametophyte
Spore germinates
Seed (Vascular) Plants
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Have true roots, leaves, and
stems
Have the ability to form
seeds, which are used for
reproduction
Seed plants are the most
dominant group of
photosynthetic organisms
on land
There are 2 types of seed
(vascular) plants:
 1. gymnosperms (cones)
 2. angiosperms (flowers)
Seed (Vascular) Plants
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Gymnosperms =
“cone bearers”
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“naked seeds” – not
enclosed in ovaries
Bear seeds directly on the
surfaces of cones
 Cones = sporophyte
structures that produce
gametophytes (seeds)
Coniferous trees are the
major example
 Pines, junipers, spruces,
etc.
section
through one
ovule
surface view of one cone scale
(houses two ovules)
Pine Life Cycle
ovule
surface view of one cone scale
(houses a pollen-producing sac)
mature
sporophyte
seed
coat
section through a
pollen-producing sac
zygote
seeding
pollen tube
spermproducing cell
Diploid
embryo
seed
fertilization
meiosis
Haploid
microspores
eggs
form
megaspores
pollination
form
female
gametophyte
Seed (Vascular) Plants
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Angiosperms = flowering plants
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Seeds are enclosed by an ovary
Flowers are reproductive organs
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Flowering plants contain ovaries
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Evolutionary advantage 
attract pollinators
Ovaries surround and protect
seeds
Ovary develops into a fruit after
pollination & helps with seed
dispersal when eaten
Examples:
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Maple trees, tulips, grass
sporophyte
Flowering
Plant Life
Cycle
Diploid
Double fertilization
Haploid
pollination
two
sperm
enter
ovule
Meiosis
microspores
female gametophyte
Meiosis
mitosis
without
cytoplasmic
division
Evolutionary Tree for Plants
Nested monophyletic groups
green zygophytes, charophytes bryophytes lycophytes
algae
related
groups
horsetails
ferns
cycads ginkgos conifers gnetophytes
flowering
plants
seed plants
euphyllophytes
embryophytes (land plants)
vascular plants
(closely related groups)
Transport in Vascular
Plants
Transport Within Plants
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Water and minerals
absorbed by roots are
drawn upward in the
xylem to the shoots
Sugar produced by
photosynthesis is
exported from leaves
to other organs via the
phloem
Transport can be
passive or active
Short- and Long-Distance
Transport in Plants
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Water and sugars move differently in
plants, depending on whether they’re
going a short or a long distance
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Ie. – walking down the street or taking an
airplane across the world
Short-Distance Transport
1. Simple diffusion/osmosis
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substances in one cell move out of
one cell, across the cell wall, and into
another cell
2. Plasmodesmata
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Plasmodesmata are connections
between the cytoplasm of adjacent
plant cells
Substances move between cells
through these openings
Long-Distance Transport
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Over long distances, these 3 processes
(simple diffusion, apoplast,& symplast) take
too long
Water and solutes move through xylem and
phloem by bulk flow, the movement of a fluid
driven by pressure
Transpiration
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Transpiration is the evaporation of water from
leaves and other parts of the plant; it causes a pull
that brings more water up through the xylem
An average maple tree loses more than 200L of
water per hour during the summer!
Unless this water is replaced by water absorbed by
the roots, leaves will wilt and die
(Cohesion-Tension Theory)
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Transpiration works through a
combination of evaporation, water
potential, adhesion, and cohesion
to pull water up the xylem
The PhotosynthesisTranspiration Compromise
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Exposing leaves to the
sun and opening
stomata (cellular
“holes” in the underside
of the leaf) to allow for
gas exchange helps
photosynthesis, but
causes transpiration to
occur at a faster rate.
Plants balance the loss
by controlling when
stomata are open.
Mechanism for Stomatal
Opening & Closing
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Guard cells open and close
stomata by changing shape
using ion and hormone
signals based on plant
stress.
Plant Structure, Growth, &
Development
The Diversity of Angiosperms
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Angiosperms
(flowering plants) can
be divided into 2
major categories:
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Monocots –
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have one seed leaf
(cotyledon)
Dicots –
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have 2 seed leaves
(cotyledons)
Monocots
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Monocots have only 1 cotyledon (seed leaf)
Examples of monocots:
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Corn, wheat, lilies, orchids, palms
Dicots
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Dicots have 2 cotyledons (seed leaves)
Examples of dicots:
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Roses, clover, tomatoes, oaks, daisies
Woody vs. Herbaceous Plants
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Angiosperms can also be subdivided into
woody (produce wood) and herbaceous (do
not produce wood) plants
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Woody plants are made of cells with thick cell
walls that support the cell body
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Examples: trees, shrubs, vines
Herbaceous plants do not produce wood as they
grow, and instead have smooth stems
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Examples: dandelions, sunflowers
Plant Life Spans
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The lifespan of plants, however, is genetically
determined
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Annuals – complete their life cycle in 1 year
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Biennials - complete their life cycle in 2 years
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Examples: marigolds, cucumbers (lots of garden plants)
Year 1: germinate & grow roots
Year 2: grow stems & leaves, produce flowers & seeds
Examples: evening primrose, celery
Perennials – live for more than 2 years
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Examples: Maple trees, grasses, palm trees
Plant Structure
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Plants are made up of
a root system and a
shoot system
The Root System
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What do roots do?
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Anchor the plant in the soil
Absorb minerals and water
Store food
Types of root systems
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Fibrous root system
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Found mostly in monocots
Taproot system
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Found mostly in dicots
How do roots grow?
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Roots grow down from the tip
in a region called the apical
meristem, where the cells are
dividing quickly
The Shoot System
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The shoot system
consists of:
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vegetative shoots (which
bear leaves)
floral shoots (which bear
flowers)
Stems have 3 important
functions:
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Producing leaves, flowers
(reproduction), branches
Holding leaves up to the
sunlight for photosynthesis
Transporting substances
between roots and leaves
How do stems grow?
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Primary growth
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Increase in length
Occurs by cell divisions in
apical meristem (at top
of shoot)
Secondary growth
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Increase in width
Occurs by cell divisions in
the lateral meristems
(outward growth)
The Shoot System: Leaves
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Leaves are the primary
photosynthetic organs of
most vascular plants
Most leaves have a
flattened blade and a
petiole, which is the
stalk that attaches the
leaf to the stem
Tissues in Plants
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All 3 plant organs
(root/stem/leaf) have
dermal, vascular, and
ground tissue systems
Dermal Tissue System
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Outer protective covering,
similar to our skin 
Protects the plant from
water loss and disease
The cuticle is a waxy
coating that helps to
prevent water loss
Tissue Systems in Plants
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Vascular Tissue System
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Carries out long-distance
transport of materials within
the plant
Xylem and phloem are
examples of vascular tissues
Ground Tissue System
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Pith (inside vascular tissue)
and cortex (outside vascular
tissue) are examples of ground
tissue
Inner cells specialized for
storage, photosynthesis, and
support
Flower Structure
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Flowers are the
reproductive structure
of angiosperms
Sepals:
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Enclose the bud before
it opens
Protect flower while it’s
developing
Petals:
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Usually brightly colored
to attract pollinators
Flower Structure
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Stamens:
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The male portion of a
flower
Made up of an anther
and a filament
The anther produces
haploid pollen grains by
meiosis
Most flowers have
multiple stamens
Flower Structure
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Carpels/Pistils:
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The female portion of a
flower
Stigma:
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Style:
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Sticky – to trap pollen
Hollow tube which
connects stigma and
ovary
Ovary:
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Produces female
gametes (ovules)
Fruit grows from an
expanded ovary
Seed Dormancy
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Seed dormancy means that a seed will not
germinate, even if sown in a favorable place,
until a specific environmental cue causes
them to break dormancy
Seed dormancy increases the chances that
germination will occur at a time and place
most advantageous to the seedling
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How did we break dormancy in our lab??
Stages of Seed Germination
(1)
(2)
(3)
(4)
The seed absorbs water,
causing it to expand and
rupture its seed coat
The embryo resumes
growth, digesting the
storage materials of the
endosperm
The radicle (embryonic
root) emerges from the
germinating seed
The shoot tip breaks
through the soil surface
Stages of Seed Germination
Plant Asexual Reproduction
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When plant species clone
themselves by asexual
reproduction, it’s known
as vegetative
reproduction
Asexual Reproduction
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Fragmentation is the
separation of a parent
plant into parts that reform whole plants
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This type of asexual
reproduction is used to
produce clones from
cuttings (common with
houseplants)
Plant Responses to
Internal & External
Signals
Plant Hormones
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REVIEW: Hormones are chemical signals
that coordinate the various parts of an
organism
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A hormone is a compound produced in one part
of the body which is then transported to other
parts of the body, where it triggers responses in
target cells and tissues
Examples of human hormones:
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Adrenaline, testosterone, estrogen, epinephrine…
Plant Hormones
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There are 5 major classes of plant hormones:
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Auxin Cytokinins
Gibberellins
Abscisic acid
Ethylene
Auxin
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Stimulates stem elongation
Stimulates fruit development
Involved in phototropism (bending to light)
and gravitropism (growing UP)
Cytokinins
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Stimulate cell division and growth
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Stimulate cytokinesis
Stimulate germination and flowering
Gibberellins
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Trigger seed and
bud germination
Promote stem
elongation and leaf
growth
Important in fruit
growth
Ethylene
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Promotes fruit
ripening
Senescence (aging)
is a progression of
irreversible change
that eventually leads
to death
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Caused, at least in part,
by ethylene
“One bad apple spoils
the whole bunch”
Abscisic Acid
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Induces seed dormancy
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Inhibits cell growth
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Anti-cytokinin
Inhibits fruit ripening
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Anti-gibberellin
Anti-ethylene
Closes stomata during
water stress, allowing
many plants to survive
droughts
Tropisms
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Tropisms are growth responses that result in
curvatures of whole plant organs toward or
away from a stimuli
There are three major stimuli that induce
tropisms
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Light (Phototropism)
Gravity (Gravitropism/Geotropism)
Touch (Thigmotropism)
Phototropism
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Phototropism is the
growth of a shoot
towards light
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This is primarily due to
the action of auxin
Auxin elongates the
cells on the non-light
side
Plant Defenses
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Plants defend themselves against herbivores
in several ways
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Physical defenses, such as thorns
Chemical defenses, such as
producing distasteful/toxic
compounds