Angiosperms
Lecturer: Asst. Prof. Dr. İsmail EKER
ANGIOSPERMS (Anthophyta-Flowering plants)
The two Seeded Tracheophyte groups are divided by
whether or not they have enclosed seeds -protected inside
a fruit or if seeds are exposed to the environment.
Tracheophytes
Seedless
Ferns use
spores
Seeded
Gymnosperms
Angiosperms
“naked” or
exposed
seeds
Flowers produce
fruit / enclosed
seeds
Angiosperms vs Gymnosperm
Angiosperm
Gymnosperms
Seeds surrounded by ovary
Seeds naked
Fruit present
Fruit absent
Flower developed
Male and female cones developed. Peranth
absent or reduced. Scales of female cone
equal to angiosperm carpel ; scales of male
cone equal to angiosperm stamen
With two fertilization - 1 sperm fertilize the With one fertilization (except Gnetophyta)
egg (embryo) while the other sperm
fertilize two central nuclei (endospermae)
Perianth segments arranged verticillate
Scales spirally arranged
Pollination with wind, insects, birds, bee
etc.
Generally with wind
Herbaceous or woody
Generally woody
Without resine channels
Generally with resine channels
Vessels present
Vessels absent (except Gnetophyta)
Sieve elements present
Sieve elements absent
Leaves expanded and pendulous (falling)
Leaves neddle-like or scale-like and
persistent (except Gnetophyta)
General characteristics of Angiosperms
• With about 250,000 known species, the
angiosperms are by far the most diverse and
widespread group of land plants.
• More than 90% of existing plant species
• Contains more than 450 families &13.000
genera; classified mainly by flower structure
• As primary producers, flowering plants are at
the base of the food web of nearly every
terrestrial ecosystem.
Taxonomy of Angiosperm
• Angiosperms are further divided into 4 major
categories:
– Basal Angiosperms (older angiosperms like Water
lilies)
– Magnoliids (Share some traits with basal angiosperms
but are more closely related to monocots and eudicots,
like the Magnolia)
– Monocotyledons
– Dicotyledons and/or Eudicotyledons
Basal
Angiosperms
Magnoloids
Monocots
Dicots
Usually spiral
arrangement
Usually spiral
arrangement
Usually whorled
Usually whorled
Often numerous
floral parts
Few to numerous
floral parts
Usually in
multiples of 3
Usually in
multiples of 4-5
Carpels sealed by Carpels sealed by
secration
cells
Carpels sealed
by cells
Carpels sealed
by cells
Carpels tubelike
Folded carpels
Folded carpels
Folded carpels
Anthers &
filaments poorly
differentieted
Anthers & filaments Anthers &
poorly
filaments
differentieted
frequently well
differentieted
Anthers &
filaments well
differentieted
seed
2-cotyledons
2-cotyledons
1-cotyledons
2-cotyledons
Leaf vein
Usually netlike
Usually netlike
Usually parallel
Usually netlike
Vascular
bundle in
stem
Usually a ring
Usually a ring
scattered
Usually a ring
Root
system
Usually taproot
Usually taproot
Usually fibrous
Usually taproot
Flower
BASAL ANGIOSPERMS
Amborella trichopoda
Star anise (Illicium
floridanum)
Water lily (Nymphaea
“Rene Gerard”)
MAGNOLIIDS
Southern magnolia (Magnolia
grandiflora)
Eudicots
Monocots
Magnoliids
Star anise
and relatives
Water lilies
Amborella
HYPOTHETICAL TREE OF FLOWERING PLANTS
Monocot and dicot traits
The dicotyledons
The monocotyledons
Palms and Bananas are Monocots
Rice, wheat, corn – all monocots
The Angiosperm Life Cycle
• In the angiosperm life cycle
– Double fertilization occurs when a pollen tube
discharges two sperm into the female
gametophyte within an ovule
– One sperm fertilizes the egg, while the other
combines with two nuclei in the center cell of the
female gametophyte and initiates development of
food-storing endosperm
• The endosperm
– Nourishes the developing embryo
• The reduced gametophytes of seed plants
are protected in ovules and pollen grains
• In addition to seeds, the following are
common to all seed plants
– Reduced gametophytes
– Heterospory
– Ovules
– Pollen
The life cycle of an angiosperm
Key
Anthers contain microsporangia.
Each microsporangium contains microsporocytes (microspore mother cells) that
divide by meiosis, producing microspores.
1
Haploid (n)
Diploid (2n)
Microsporangium
Anther
Microsporocytes (2n)
Mature flower on
sporophyte plant
(2n)
2 Microspores form
pollen grains (containing
male gametophytes). The
generative cell will divide
to form two sperm. The
tube cell will produce the
pollen tube.
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n)
7 When a seed
germinates, the
embryo develops
into a mature
sporophyte.
Generative cell
Tube cell
Male gametophyte
(in pollen grain)
Ovary
Stigma
3 In the megasporangium
of each ovule, the
megasporocyte divides by
meiosis and produces four
megaspores. The surviving
megaspore in each ovule
forms a female gametophyte
(embryo sac).
Embryo (2n)
Endosperm
(food
Supply) (3n)
6 The zygote
develops into an
embryo that is
packaged along
with food into a
seed. (The fruit
tissues surrounding the seed are
not shown).
Pollen
grains
MEIOSIS
Germinating
Seed
Seed
Megasporangium
(n)
Pollen
tube
Sperm
Surviving
megaspore
(n)
Seed coat (2n)
Pollen
tube
Style
Female gametophyte
(embryo sac)
Antipodal cells
Polar nuclei
Synergids
Egg (n)
Pollen
tube
Zygote (2n)
Nucleus of
developing
endosperm
(3n)
Egg
Nucleus (n)
Sperm
(n)
4 After pollination, eventually
two sperm nuclei
are discharged in
each ovule.
FERTILIZATION
5 Double fertilization occurs. One sperm
fertilizes the egg, forming a zygote. The
other sperm combines with the two polar
nuclei to form the nucleus of the endosperm,
which is triploid in this example.
Discharged
sperm nuclei (n)
Parasitic Plants
• Derive all or some nutrients from host
plant
• Parasitic plants have a modified root, the
haustorium, that penetrates the host plant
and connects to the xylem, phloem, or
both, in stems or roots of the host plant.
• Examples: Mistletoe, Dodder, Rafflesia
Viscum albumMistletoe- Ökseotu
Cuscuta japonicaJapanese DodderCinsaçı
Rafflesia
• World’s the
biggest flower
• IndonesiaSumatra & Borneo
•Up to 1 m diam
•10 kg
•Lives only one
week
Carnivorous Plants
• Grow in nutrient poor soil such as bogs.
• High acidity in bogs prevents growth of muchneeded nitrogen cycle bacteria
• Most plants cannot grow in such soil
• Carnivorous plants evolved a mechanism to trap
and digest insects
• This adaptation helped them overcome the
nitrate dilemma
• Examples: Pitcher plants, sundews, Venus flytrap
Dionea
(Venus flytrapSinekkapan, böcekkapan)
Utricularia (Bladderwort-sumiğferi)
Venus Flytrap
Drosera (Sundews-Güneşgülü)
Nephenthes
(Pitcher plant -sürahi ,
maşrapa bitkisi )
Epiphytes
• Plants that attach to other plants
• Epiphytes usually derive only physical
support and not nutrition from their host,
though they may sometimes damage
the host. Hence, they are NOT
parasitic
• They do this to get more light and rain
water in a rainforest canopy
Bromeliad
Orchid
Plant Morphology
Plant types
• Herbs
• Shrub
• Tree
• Vine or liane
Flowers
Fruits
Leaves
Stem
Roots
Plant parts
• Vegetative parts (root, stem, bud, leaf)
• Generative parts (flower, fruit, seed)
Flowering
Plant
Morphology
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical
bud
Vegetative
shoot
Leaf
Shoot
system
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral
branch
roots
Root
system
Plant Morphology - Roots
•Roots are multicellular
organs with important
functions:
Anchoring the plant
Absorbing minerals and water
Storing organic nutrients
• Millions of tiny roots
hairs in these tip
areas help
absorption by
increasing surface
area
Roots - Comparisons
Taproot
• 1 main root
• Smaller secondary roots
• Strong anchorage
• Absorbs deep water
Fibrous
• No main root
• Fast absorption of surface water
• Holds soil – prevention of erosion
Taproots
Typical of dicots, primary
root forms and small
branch roots grow from it
Fibrous roots
In monocots mostly,
primary root dies, replaced
by new roots from stem
•A taproot system consists of one main
vertical root that gives rise to some large
lateral roots, or branch roots.
•Adventitious roots arise from stems or
leaves.
•Seedless vascular plants and monocots have
a fibrous root system characterized by many
thin lateral roots with no main root.
•In most plants, absorption of water and
minerals occurs near the root hairs, where
vast numbers of tiny root hairs increase the
surface area.
Plant Morphology - Stems
• Herbaceous
Plant
Plant Morphology- Leaves
Leaves are the major photosynthetic parts of most plants.
They are borne at the nodes of a stem, usually below a bud.
They are usually flat, and have one surface facing towards
the stem axis (the adaxial, or upper, surface) and another
surface facing away from the stem axis (the abaxial, or lower,
surface).
Type of leaves
– Simple = blade not divided into smaller leaflets
– Compound = blade divided into smaller parts that look
like small leaves (but lack axillary buds)
Leaf Structure - A leaf with a single blade is termed simple; a leaf with two or more
blades, or leaflets, is said to be compound. The distinction between simple and
compound leaves can be made by locating the axillary bud: an axillary bud is subtended
by an entire leaf and never by individual leaflets.
Plant Morphology - FLOWER
The Flower — What is it?
• a flower is a specialized shoot that:
1. has a modified stem with compressed internodes
2. possesses modified leaves with various functions
3. often clustered in an inflorescence (larger branch)
The Flower
5. Perianth: collective term for
sepals and petals (Tepals if both
similar)
4. Petal: the second whorl of
leaves, typically brightly colored,
attracting pollinators; collectively
called the corolla
1. Peduncle: floral stalk, the stem
supporting the flower; sometimes
referred to as the pedicel
3. Sepal: the outer whorl of leaves,
green and protection; collectively
called the calyx
2. Receptacle: modified floral
stem or axis from which arise
the floral appendages or
modified leaves
The Flower
8. Stamen: the male structure of
flower comprising filament and
anther
• collectively, stamens are the
androecium (= ‘house of
males’)
• can be leaf-like in primitive
angiosperms
6. Filament: slender stalk of the stamen
supporting the anther; permits exsertion of
pollen out of flower
7. Anther: fertile portion of stamen that
dehisces to release pollen grains;
composed of anther sacs
The Flower
13. Pistil: flask-shaped, female
structure comprising three
main parts
• often referred to as carpel(s)
• all pistils (1 or more) are
referred to as the gynoecium
(= ‘house of females’)
9. Ovary: basal portion of pistil that contains
ovules; at maturity becomes fruit with seeds
10. Ovules: fertile portions of pistil that
contain a female gametophyte (embryo sac);
develop into seeds after fertilization
12. Stigma: receptive portion
at top of style that receives
and recognizes pollen
11. Style: slender stalk of pistil
above ovary that the pollen
tubes must pass through to
reach eggs in ovules
Plant Morphology - Fruit
= “mature ovary”
purpose: protects seeds, dispersal aid
Relationship between a pea flower and a fruit (pea pod)
Fruit or vegetable?
• botanical:
– Ripened ovary
• Legal
– Something that tastes sweet and is eaten as
dessert
Pericarp
• The pericarp is what develops from the ovary wall.
It has three layers that widely in structure depending
on the fruit:
• Exocarp – The outer layer.
• Mesocarp – The middle layer.
• Endocarp – The inner layer.
Seeds
Seeds develop from ovules and contain embryonic
plant plus nutritive tissue & tough outer coat
Embryo. Young sporophyte consisting of epicotyl, hypocotyl, radicle, and one or more cotyledons.
Endosperm. Food reserve tissue in seed derived from fertilized polar nuclei; or food reserve derived from megametophyte
in gymnosperms.
Hilum. Funicular scar on seed coat.
Micropyle. Hole through seed coat.
Seed Coat. Outer protective covering of seed.
Coleoptile. Protective sheath around epicotyl in grasses.
Coleorhiza. Protective sheath around radicle in grasses.
Cotyledon. Embryonic leaf or leaves in seed. Used for food until the 1st true leaves emerge and the new plant can start to
photosynthesis
Epicotyl. Apical end of embryo axis that gives rise to shoot system.
Hypocotyl. Embryonic stem in seed, located below cotyledons.
Plumule. Embryonic leaves in seed derived from epicotyl.
Radicle. Basal end of embryo axis that gives rise to root system.