Angiosperms

Lecturer: Asst. Prof. Dr. İsmail EKER

Tracheophytes

Seedless Seeded

Ferns use spores

Gymnosperms Angiosperms

“naked” or exposed

seeds

Flowers produce fruit / enclosed

seeds

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.

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 egg (embryo) while the other sperm fertilize two central nuclei (endospermae)

With one fertilization (except Gnetophyta)

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)

Angiosperms vs Gymnosperm

• 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.

General characteristics of Angiosperms

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

Flower 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 secration

Carpels sealed by cells

Carpels sealed by cells

Carpels sealed by cells

Carpels tubelike Folded carpels Folded carpels Folded carpels

Anthers & filaments poorly differentieted

Anthers & filaments poorly differentieted

Anthers & filaments 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

Amborella trichopoda Water lily (Nymphaea “Rene Gerard”)

Star anise (Illicium floridanum)

BASAL ANGIOSPERMS

HYPOTHETICAL TREE OF FLOWERING PLANTS

MAGNOLIIDS

Am

bo

rell

a

Wat

er l

ilie

s

Sta

r an

ise

and

rel

ativ

es

Mag

no

liid

s

Mo

no

cots

Eu

dic

ots

Southern magnolia (Magnoliagrandiflora)

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 angiospermKey

Mature flower onsporophyte plant(2n)

Ovule withmegasporangium (2n)

Female gametophyte(embryo sac)

Nucleus ofdevelopingendosperm

(3n)

Dischargedsperm nuclei (n)

Pollentube

Male gametophyte(in pollen grain)

Pollentube

Sperm

Survivingmegaspore(n)

Microspore (n) Generative cell

Tube cell

Stigma

OvaryMEIOSIS

MEIOSIS

Megasporangium(n)

Pollengrains

EggNucleus (n)

Zygote (2n)

Antipodal cellsPolar nucleiSynergidsEgg (n)

Embryo (2n)

Endosperm(foodSupply) (3n)

Seed coat (2n)

Seed

FERTILIZATION

Haploid (n)

Diploid (2n)

Anther

Sperm(n)

Pollentube

Style

Microsporangium

Microsporocytes (2n)

GerminatingSeed

Anthers contain microsporangia.Each microsporangium contains micro-sporocytes (microspore mother cells) thatdivide by meiosis, producing microspores.1

Microspores formpollen grains (containingmale gametophytes). Thegenerative cell will divideto form two sperm. Thetube cell will produce thepollen tube.

2

In the megasporangiumof each ovule, themegasporocyte divides bymeiosis and produces fourmegaspores. The survivingmegaspore in each ovuleforms a female gametophyte(embryo sac).

3

After pollina-tion, eventuallytwo sperm nucleiare discharged ineach ovule.

4

Double fertilization occurs. One spermfertilizes the egg, forming a zygote. Theother sperm combines with the two polarnuclei to form the nucleus of the endosperm,which is triploid in this example.

5

The zygotedevelops into an

embryo that ispackaged alongwith food into aseed. (The fruit

tissues surround-ing the seed are

not shown).

6

When a seedgerminates, the

embryo developsinto a mature

sporophyte.

7

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

Cuscuta japonica-Japanese Dodder- Cinsaçı

Viscum album-Mistletoe- Ökseotu

Rafflesia

• World’s the biggest flower

• Indonesia- Sumatra & 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 much-

needed 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 fly-

trap

Venus Flytrap

Nephenthes(Pitcher plant -sürahi , maşrapa bitkisi )

Utricularia (Bladderwort-sumiğferi)

Drosera (Sundews-Güneşgülü)

Dionea(Venus flytrap-Sinekkapan, böcekkapan)

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 parts• Vegetative parts (root, stem, bud, leaf)• Generative parts (flower, fruit, seed)

Plant types• Herbs• Shrub• Tree• Vine or liane

Fruits

Flowers

Roots

StemLeaves

Flowering Plant Morphology

Reproductive shoot (flower)

Apical bud

Node

Internode

Apicalbud

ShootsystemVegetative

shoot

LeafBlade

Petiole

Axillarybud

Stem

Taproot

Lateralbranchroots

Rootsystem

• Millions of tiny roots hairs in these tip areas help absorption by increasing surface area

• Roots are multicellular organs with important functions:

Anchoring the plantAbsorbing minerals and waterStoring organic nutrients

Plant Morphology - Roots

Taproots Fibrous rootsTypical of dicots, primary root forms and small branch roots grow from it

In monocots mostly, primary root dies, replaced by new roots from stem

Roots - Comparisons

Fibrous• No main root• Fast absorption of surface water• Holds soil – prevention of erosion

Taproot• 1 main root• Smaller secondary roots• Strong anchorage• Absorbs deep water

• 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

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).

Plant Morphology- Leaves

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.

• 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 — What is it?

Plant Morphology - FLOWER

2. Receptacle: modified floral stem or axis from which arise the floral appendages or modified leaves

3. Sepal: the outer whorl of leaves, green and protection; collectively called the calyx

4. Petal: the second whorl of leaves, typically brightly colored, attracting pollinators; collectively called the corolla

5. Perianth: collective term for sepals and petals (Tepals if both similar)

1. Peduncle: floral stalk, the stem supporting the flower; sometimes referred to as the pedicel

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

The Flower

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 Flower13. 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.

SeedsSeeds 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 photosynthesisEpicotyl. 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.