Botany

WORLD’S #1 ACADEMIC OUTLINE

BarCharts, Inc.®

• Study of the Plant Kingdom... Our Essential Partners in Life •
ALTERNATION OF GENERATIONS

INTRODUCTION
What’s so special about plants?
• They are photosynthetic, using the ultimate energy
source, the sun, to make their own food. For this reason
they are called autotrophs. Plants power most
ecosystems and are thus essential to life on Earth.

Have you thanked a plant today?

GAMETE EVOLUTION
Plants have developed different strategies for gamete
production and fusion.
• Isogamy – Gametes are equally motile and of similar
size.
• Anisogamy – One gamete
Female(+) Male(-)
is large and less motile,
with nutrient reserves,
while the other is smaller
and more motile, with few
nutrient reserves.
• Oogamy – One gamete is
non-motile and large, with
large nutrient reserves

(egg), while the other is
smaller and motile
(sperm) and must
locate
the
larger
gamete.

Isogamy

A unique evolutionary strategy for reproduction where a single plant organism has
two phases to its life history.
• Gametophyte – Haploid, multicelled
individual produces gametes via mitosis.
Dominant form in lower plants.
• Sporophyte – Diploid, multicelled individual
from gamete fusion (zygote); produce haploid
spores via meiosis for dispersal; spores
germinate via mitosis to produce gametophytes. Dominant form in higher plants.
• Isomorphic A/G – Gametophyte and sporophyte individuals are morphologically indistinguishable.
• Heteromorphic A/G – Gametophyte and
sporophyte individuals are morphologically
distinct.

PLANT CLASSIFICATION
SEEDS, VASCULAR
Angiosperms

Oogamy
Gymnosperms

PLANT EVOLUTION

• New problems on land: Plants must adapt to living
in the air, a non-aquatic, dry medium. This presents
some problems:
- Obtaining water and preventing water loss.
- Transporting water and nutrients.
- Gas exchange (requires moisture)
- Gravity
- Reproduction when gametes swimming in water is
limited.
- Temperature flux of air is more rapid than in
water.
Plant adaptations/solutions
• Chlorophyll A & B, to capture sunlight – similar to
green algae chlorophyll.
• Starch storage, for prolonged inactive periods during
seasonal variations.
• Gametes protected and kept moist inside plant
tissues.
• Stomata (leaf openings) to regulate gas exchange.
• Wax surfaces to prevent excess water loss.
• Root system to pull in water and nutrients from
soil.
• Conduction tissues to transport water, nutrients
and food.
• Support tissues to battle gravity for vertical growth.
• All of these adaptations have greatly enhanced the
success of plants on land today.

Spore
n
n

n

Antheridium

Archegonium
Sperm

Egg

n Spores

Syngamy

Meiosis

2n

2n Spore mother cell

Zygote
2n

Embryo

Sporangia

Diploid

Sporophyte
(2n)

NONVASCULAR PLANTS
1st Plants on Land
• Lack vascular tissues
• Gametophyte is dominant, sporophyte nutritionally
dependent on gametophyte.
• Small; live in moist environments; gametes released
into water.
a. Division Hepatophyta (Liverworts)
b. Division Anthocerophyta (Hornworts)
c. Division Bryophyta (Mosses)

Anisogamy

Plant evolution: Land colonization occurred about 400
mya, likely from aquatic, green algae ancestor.

Haploid
Gametophyte
(n)

(a)

(b)

SEEDLESS, VASCULAR
Ferns

Club Mosses
Sporophyte
Gametophyte

Horsetails

Growing
region
Foot of
sporophyte

Whisk Ferns

(c)
Capsule

NONVASCULAR

Sporophyte
Mosses

Seta
Foot

Liverworts

Hornworts

GREEN ALGAL ANCESTOR
1

Gametophyte


SEEDLESS VASCULAR PLANTS

SEED “Ferns”

Microphyll Evolution
Stem

Microphyll

Vascular
tissue
Vascular
Projection supply to
projection

Unbranched
stem

Leaf with
one vein

Extinct fossil forms that
may show transition from

seedless vascular plants
(e.g., ferns) to vascular
seed
plants
(e.g.,
gymnosperms
and
angiosperms).

Megaphyll Evolution

FLOWERS

Main axis of stem

Dichotomously
branching stems

Side
branch

Overtopping
(one branch becomes
main axis of stem)
Megaphylls

Leaves with
many veins
Webbing of side
branch systems

• Most plants are angiosperms and thus produce
flowers with both male and female reproductive
structures.
• Flower anatomy
- Sepals, petals
- Stamen (Male Portion): Anther, filament
- Pistil (Carpel, Female Portion): Stigma, style,
ovary, ovule

{

The pistil
contains
the female
organs

Stigma
Style
Ovary
Ovule

Petal

{

Seedless Vascular plants
• Possess xylem & phloem for transport of materials.
• Sporophyte is dominant.
• Evolution of leaf for efficient light capture.

- Microphylls, megaphylls (In botany, the prefixes
"micro" and "mega" generally refer to similar
structures in male and female parts of the plant,
respectively).
• Division Lycophyta (Club Mosses)
- Roots present.
- Leaves present (microphylls).
• Division Psilophyta (Whisk Ferns) No roots or leaves
• Division Sphenophyta ( Horsetails)
- Roots present.
- Stems contain silica.
- Leaves present (microphylls).
- Division Pterophyta (Ferns)
- Roots present.
- Leaves (= fronds)
- Fronds present (megaphylls).
- Fern life history (see fig. below)
- Sporophyte, sori, sporangia, spores, gametophyte
(= prothallus), archegonium with eggs and
antheridium with sperm
• The Plant Scene (300 mya): Many seedless vascular
plants and some nonvascular plants exhibited lush,
dense growth covering large expanses in Earth’s history.
• Much of today’s oil, coal and gas deposits were
formed by these plants.
Evolution of the "seed" plants
• Terrestrial adaptations of seed plants.
- Gametophytes protected in moist sporophytic,
reproductive tissues.
- Pollination replaced swimming for sperm delivery to egg.

- The seed evolved - a dormant embryo with
surrounding nutrients protected from environmental conditions. Seeds replaced spores as
dispersal agents, using wind, water or animals.
• The seed - a fertilized egg
- Inside an ovule.
- Integument, megasporangium ➔ megaspore
‘gametophyte ➔ egg sperm

Anthers
(microsporangia)

The stamen
contains
the male
organs

OVULE TO SEED
Megasporangium (2n)

Seed coat (2n) (derived from integument)

Integument (2n)
Spore case (n)

Female
gametophyte (n)

Pollen
tube (n)

Egg
nucleus
(n)

Micropyle

Food
supply
(derived
from
female
gametophyte
tissue)

Discharged sperm nucleus (n)
Embryo (2n) (new sporophyte)
Megaspore (n)

(b) Fertilized ovule

(a) Ovule

Filament

Sepal

Receptacle

(c) Seed

FERN LIFE HISTORY
The sporophyte
(still attached to
the gametophyte)
grows, develops

rhizome

zygote

sorus

Diploid Stage
fertilization
Archegonium
egg

egg
producing
structure

sperm

sperm
producing
structure

meiosis

Haploid Stage

Sporangia
The spores are
released from a
spore chamber

Spores develop
Prothallus
mature
gametophyte
(underside)

A spore
germinates and
grows into a
gametophyte

Antheridium

TRENDS IN ALTERNATION OF GENERATIONS
Gametophyte (n)

Sporophyte (2n)
Gametophyte (n)

Sporophyte (2n)
Sporophyte (2n)

• Sporophyte dependent on gametophyte (e.g., bryophytes)

Gametophyte (n)

• Large sporophyte and small, independent gametophyte (e.g., ferns)
• Reduced gametophyte dependent on sporophyte (seed plants)
2

• Angiosperms have dominated the plant scene since the
demise of dinosaurs and many gymnosperms
(Cenozoic era, 65 mya to present).
• Seed in a protective container or cotyledon
• Angiosperm life cycle:
- Microspore mother cell ➔ microspores ➔ pollen
grain (male gametophyte)which includes tube cell
and generative cell (sperm)
- Megaspore mother cell ➔ megaspore ➔ embryo
sac with 7 cells and 8 nuclei (female gametophyte)
➔ egg
- Two sperm move through the pollen tube and
engage in a double fertilization (where one sperm
fuses with the egg to form a zygote/embryo, and the
other sperm fuses with a large, central cell to form
endosperm/nutrient reserve for the embryo) until it
can produce its first leaves and begin photosynthesis.
- Pollination and fertilization occur within hours to
days, making angiosperms quick reproducers,
compared to gymnosperms.
• Flowers ensure pollination by insects, birds and
mammals.
- Flowers and pollinators co-evolved.
• Seed dispersal

- Important because plants may drop seeds close by,
but new individuals will possibly compete with
parent plants.
- Wind, water and animals are common
dispersal agents.
- Fruits can entice animals to aid in dispersal.
• Fruits – ripened ovary (see fig.)
• Monocots and Dicots - two major groups of
angiosperms (see fig. for differences)
- Monocots include grasses, corn, sugar cane, palm
trees, lilies and orchids.
- Dicots include most trees, vines, shrubs and cacti.


THE GYMNOSPERMS - “naked seed” plants
• Dominant plant when dinosuars ruled
(Mesozoic era, 220 - 65 mya).
• Do not produce flowers.
• Ovules/seeds exposed.
• Division Cycadophyta
- Slow-growing palm-like trees found
primarily in tropics and sub-tropics.
• Division Ginkgophyta
- Only one living member.
- Ginkgo
biloba
(common
diet
supplement)
• Division Gnetophyta

- Closest living relatives of angiosperms
- Ephedra
- Drug ephedrine originally derived from this
plant.
- Cells resemble xylem vessel cells of
angiosperms.
- Cone clusters resemble flowers.
• Division
Coniferophyta
(Conifers,
Evergreens)
- Oldest, tallest, most massive plants (e.g.,
380 ft. tall Redwood tree).
- Leaves form needles, which slow desiccation
and are resistant to grazing by herbivores.
- Important economically as wood/paper
source, resin, turpentine and Christmas
trees
• Pine life cycle:
- Ovulate cone = megastrobilus with megasporophylls (scales) - Micropyle, where
pollen lands on ovulate cone.
- Pollen cone = microstrobilus with
microsporphylls
- The process from pollination to fertilization
can take over a year, which proved slow
once the angiosperms evolved.

GYMNOSPERM LIFE CYCLE
Megaspore(n)
Scale of

female cone
Female cone

HAPLOID
Gametophyte
generation
Megasporangium
Ovule

Male cones

Pollen
chamber

Note that the same plant has both
pollen-producing male cones and
egg-producing female cones

Micropyle
Female

MEIOSIS gametophyte(n)

Egg
Microspores(n)
Microspore
Reduced
mother cells(2n)
archegonium

Germinating pollen
produces pollen tubes
to reach the egg.
Male gametophyte
(germinating pollen
grain)

Pollen
grain

FERTILIZATION
Scale of
male cone

Sporophyte(2n)

The gametophytes
are tiny

DIPLOID
Sporophyte
generation

Female
gametophyte(n)

Seed coat
Suspensors
Seed
Female

gametophyte

Zygotes(2n)
Winged seed

Embryo
Female cone
Developing embryo

Wing

The seed protects
the embryo

Scale of
female cone

THE ANGIOSPERMS - “enclosed seed” plants
FRUIT DEVELOPMENT
Endosperm

ANGIOSPERM LIFE CYCLE

Primary
endosperm
cell

Pollen grains (n)
Generative cell

Anther

Fruit flesh

Ovary

Meiosis
Integument

Seed coat
Tube cell
Fruit

Microspores (n)
Anther

Pollen mother
cells (2n)

Stigma

Functional
megaspore (n)
Megaspore
mother cell (2n)

Pollen
tube

8-nucleate

embryo sac
(megagametophyte)
(n)

Zygote

Embryo

MONOCOTS VS DICOTS
MONOCOTS

DICOTS

Sperm
cells

Florals parts in
multiples of 4 of 5

Floral parts in
multiples of three

Meiosis

Ovary
Adult
sporophyte
(2n) with
flowers
Germination

LEAVES

Ovule
Seed (2n)
Endosperm (3n)

Double
fertilization

Formation of
pollen tube (n)

Long tapering blades
with parallel venation

Broad to narrow leaves
with netted venation

STEMS

Seed
coat
Egg
Vascular bundles
are scattered

Vascular bundles
arranged in a circle

SEEDS

Endosperm (3n)
Embryo (2n)

Contain 1 cotyledon

3

Flower

Contain 2 cotyledons


PLANT ARCHITECTURE

STEM STRUCTURE

• Plant needs and solutions:
- Leaves - Collection and conversion of solar energy
- Stems - Positioning and support of leaves
- Roots - Anchorage and absorption
- Vascular system - Transport
Axillary bud

•
•
•
•

Cellulose-based cell walls for support and growth toward sunlight
Epidermis
Dicots with cortex and pith separated by ring of vascular bundles.
Monocots with ground tissue with scattered vascular bundles.

Shoot tip
(terminal bud)

Vessels Meristematic cell
in xylem (brick-shaped cells)

Epidermis
Vascular
bundle

Young leaf

Cortex

Pith

Flower

Node
Internode

Epidermis

Node

Transverse section of a stem,
with enlargement of a vascular
bundle shown to the right

Leaf
Ring of vascular
bundles divides
ground tissue into
cortex and pith

Vascular
tissues

Sieve-tube members
and companion cells
in phloem

Seeds
(inside fruit)

Air space Vessel in xylem

Epidermis

Thick-walled
sclerenchyma
cells forming
a sheath
around the
mature

vascular
bundle

Ground
tissue

Ground tissues

Vascular
bundle

Withered
cotyledon

Fibers in phloem

Shoot system
Root system

Root hairs
Primary root

Root tip
Root cap

Lateral root

Groundvascular bundles
distributed through
ground tissue

Transverse section of a stem,
with enlargement of a vascular
bundle shown to the right

ROOT STRUCTURE

LEAF STRUCTURE
•
•
•
•
•
•

Sieve-tube member Companion cell
in phloem
in phloem

Epidermis
Cuticle with wax to resist desiccation (produced by epidermis).
Guard cells with stomata to regulate gas exchange.
Mesophyll - Photosynthetic layer.
Dicots with palisade and spongy layers; monocots with one layer.
Vein - Vascular bundle for transport of materials.

Epidermis
Endodermis

Root section

Palisade
mesophyll

Cortex
Casparian
strip

Vein
vascular
bundle

Endodermis
Upper
epidermis

Casparian strip

Cuticle

•
•
•
•
•

Bundle
sheath
Xylem
Stoma
Lower

epidermis

Stoma

Guard cells

Spongy
mesophyll

4

Movement of water through
the endodermis to the center
of the root

Epidermis - Has root hairs for increased absorption area for water/minerals.
Cortex
Endodermis - With casparian wax strips
Stele - Central cylinder with vascular tissues inside
Apoplastic pathway vs. symplastic pathway: Water enters through root
epidermis and passes in the spaces "between" cortex cells apoplastically unti
reaching the endodermis. Casparian strips prevent water from passing
between endodermal cells. Thus, water is forced through the cell membranes
symplastically where it is filtered before reaching the vascular tissues within
the stele. In this way, potentially harmful substances might be removed by the
selectively-permeable membranes of the endodermal cells.


PLANT DEVELOPMENT

VASCULAR TISSUES
• Xylem, used for water/mineral transport.
- Tracheids - Thin, hollow, dead cells
with perforated, tapered ends.
- Vessel members (element) - Thick,
hollow, dead cells with large holes
on end.
• Phloem used for sugar/food transport.
- Sieve tube members (element),
hollow, living cells with perforated ends.
- Companion cells, living cells that
help keep sieve tube member cells
alive.

Pits in wall

Sieve plate
One vessel member

no
cytoplasm
(cells are
dead at
maturity)

MERISTEMATIC TISSUES
• Growth after germination
• Upward growth
- Epicotyl or Coleoptile
- Phototropism - Plant

growth and movement in
response to light.
• Downward growth
- Radicle or hypocotyl
- Gravitropism - Plant
growth response to gravity
via statolith sensors.
• Meristematic tissues form all
tissues of adult plant (similar
to germ tissues of animals).
• Apical meristems
- Responsible for increase
in plant height.
• Lateral meristem
- Responsible for increase
in plant diameter (girth).
• Three primary meristems:
- Protoderm - Epidermis
- Ground meristem Cortex and ground tissues
- Procambium - Vascular
bundles with xylem and
phloem.

sievetube
member
(alive)
companion
cell
(alive)
Portion of

one vessel

Portions of
tracheids

Portion of
one sieve tube

IMPORTANT SYMBIOSES WITH PLANTS
• Root nodules & bacteria
- Bacteria fix nitrogen and are housed in root nodules to supply
"fertilizer," thus allowing the plant to thrive, even in soils that
are nutrient poor.
• Mycorrhizae
- Most plants today have an association between their roots and
fungi in the soil. This association, or mycorrhizae, is critical in
aiding water/mineral uptake by the plant.

VEGETATIVE (asexual) REPRODUCTION
Plants typically produce new
parts/structures without sexual reproduction, thus allowing the quick spread
of the plant into the immediate habitat.

Fleshy leaves
Stem

Stem

Corm

Bulb

Apical Meristem

Protoderm
Ground
meristem
Procambium
Three Primary Meristems:

Vascular bundle
Vascular
cambium

Stem of
primary
plant body

Cork
cambium

Lateral Meristems
(their location in
stems showing
secondary growth)

SEEDLING DEVELOPMENT
Foliage leaves

New plant

Cotyledon

Stolon (runner)

Epicotyl
Rhizome
Cotyledon

Root

Cotyledon

Hypocotyl

Hypocotyl

Asexual Reproductive Modes of Flowering Plants
Mechanism

Representative

Characteristics
Radicle

Vegetative reproduction on modified stems
Runner (stolon)

Strawberry

Rhizome
Corm

Bermuda
grass
Gladiolus

Tuber

Potato

Bulb

Onion lily

Parthenogenesis

Orange tree,
rose

Vegetative
propagation

Jade plant,
African
violet

Tissue
culture
propagation

Orchids,
lily, tulip,
wheat, rice,
corn

New plants arise at nodes on an
above ground horizontal stem
New plants arise at nodes of
underground horizontal stem
New plant arises from axillary
bud on short, thick, vertical
underground stem

Seed coat

Bean

Foliage leaves
Epicotyl

Hypocotyl

Cotyledon

New shoots arise from
axillary buds on tubers
(enlarged tips of slender
underground rhizomes)

Hypocotyl
Radicle

New bulb arises from axillary
bud on short underground
stem
Embryo develops without
nuclear or cellular fusion
(e.g., from unfertilized
haploid egg; or develops
adventitiously, from tissue
surrounding embryo sac)
New plant develops from
tissue or organ (e.g., a leaf)
that drops or is separated
from plant
New plant induced to arise
from cell of a parent plant that
is not irreversibly differentiated

Pea
Coleoptile

Radicle

Corn
5

Foliage
leaves

Plant development continued:
• Vascular cambium - Produces xylem inward and phloem outward
• Cork cambium - Cork
• Wood is produced from xylem:
- Annual rings (see fig.)
- Heartwood vs. sapwood (see fig.)
- Heartwood - Clogged xylem, little water transport
- Sapwood - Newer xylem, free flowing water transport
• Bark is produced from phloem, cork cambium, cork
- Lenticels are cracks in the bark to facilitate gas exchange.
- "Girdling plants" or cutting a horizontal band around the
circumference of the plant, can be deadly because the vascular
cambium, in which nutrients and water travel vertically, can be
damaged. Lawn equipment (especially weed whackers) is a
potential source of this kind of plant damage.
• Exchange and Transport
- Plants obtain gases, nutrients, minerals and water via internal
fluids.
- Gas exchange- stomata, roots, lenticels
- Internal transport- xylem and phloem
- Fluids move in xylem via adhesion, cohesion, evaporation and
osmosis.
• Theories of upward movement:
- Capillary action - Some water moves up small vascular cells
naturally.
- Root pressure - Solutes inside the root tissues draw some
water up.
- Transpiration pull (cohesion-adhesion-tension)- The main

motive force for transporting water up to the top of a plant
(sometimes several hundred feet).
- Essentially, as water evaporates from the leaf surface, the
cohesive and adhesive properties of water pull water molecules
from below, establishing a water tension/pressure. One
drawback is it requires loss of water from the plant. In dry
conditions or arid environments, this water loss for vertical
transport can be critical to plants – thus, a replenishing water
supply in the roots is vital.
• Fluid movement in phloem (see fig.)
- Sugars produced by the leaves via photosynthesis must be
distributed to the rest of the plant. Gravity can assist this
basically downward movement. However, getting the sugars into
the cells of the phloem requires energy (i.e. active transport).
Sometimes large quantities of sugars/starch are stored in special
vegetative structures (e.g., tubers).

SECONDARY GROWTH
Xylem
Heartwood
Cork (with cambium)

"Bark"

Vascular cambium

ANNUAL RINGS
1993

1992

Annual ring
1991

1990
250 um

INTERNAL TRANSPORT IN PHLOEM
Xylem

Phloem

Companion cell

This QUICKSTUDY ® guide is an outline of the basic topics taught in Botany
courses. Due to its condensed format, use it as a Botany guide but not as a
replacement for assigned class work.

Leaf
(source of sucrose)

All rights reserved. No part of this publication may be reproduced or transmitted in any form, or
by any means, electronic or mechanical, including photocopy, recording, or any information
storage and retrieval system, without written permission from the publisher.
© 2001 BarCharts, Inc., Boca Raton, FL 1007

CREDITS
Author: Randy Brooks, PhD.
Layout: Dale Nibbe

Sapwood

Phloem

PRICE
U.S. $5.95
CAN. $8.95

Bulk flow
of solution

Plasmodesmata

ISBN-13: 978-142320405-3
ISBN-10: 142320405-0
Fruit
(sink for sucrose)

free downloads &

hundreds of titles at

quickstudy.com
Customer Hotline #
1.800.230.9522
We welcome your
feedback so we can
maintain and exceed
your expectations.

Sieve

Companion cell

Water
Sucrose
6

osmosis of water
active transport of sucrose