SEED PLANTS IISEED PLANTS IIThe Flowering Plants (Anthophyta)

Anthophyta

Phylum Anthophyta Phylum Anthophyta (Angiosperms)(Angiosperms)

Constitutes ~300,000 species (Gymno. 720 spp) Most recently evolved & most diverse group Divided into many groups:

Basal AngiospermsMagnoliids (~8500) Eudicotyledones (dicot)Monocotyledones (monocot)

Phylogeny of AngiospermsPhylogeny of Angiosperms

Basal angiosperms

Fusion

From Endress & Igersheim, 2000

Fusion of CarpelFusion of Carpel

fusionsecretion

Characteristics of AngiospermsCharacteristics of Angiosperms Double fertilization:

egg + sperm produce zygote (2n)egg + 2nd sperm produce endosperm (3n)

Mostly closed carpels: enclose ovule Reduced gametophytes (pollen grain, embryo sac) Sieve tubes and companion cells (phloem) Vessels (xylem) Stamens with 2 pairs of pollen sacs Chemical evolution!

Refinements in vascular tissue, especially xylem, probably played a role in the enormous success of angiosperms in diverse terrestrial habitats.Like gymnosperms, angiosperms have long,

tapered tracheids that function for support and water transport.

Angiosperms also have fiber cells, specialized for support, and vessel elements (in most angiosperms) that develop into xylem vessels for efficient water transport.

The plant is dioecious. Female flowers with 5-6 carpels (a). Male flowers 10-25 stamens (b).

AmborellaAmborella ( (Basal angiospermsBasal angiosperms))

http://www.amborella.org/ Scott Zona

Fruit

mailto:stephens@cats.ucsc.edu

Scott Zona

Fruit: aggregate follicle

Magnolia (Magnoliids)

Tulip (Magnoliids)

Differences Between Monocot Differences Between Monocot & Eudicot& Eudicot

MONOCOT Embryo with single cotyledon Pollen with a single furrow or

pore* Flower parts in multiples of

three Major leaf veins parallel Stem vascular bundles

scattered Have fibrous roots Secondary growth absent

EUDICOT Embryo with two cotyledons Pollen with three furrows or

pores Flower parts in multiples of four

or five Major leaf veins reticulate Stem vascular bundles in a

ring Have taproots Secondary growth often present

Pollen of Horse chestnutPollen of Horse chestnutA Grass Pollen

Flower: the main feature of angiospermsFlower: the main feature of angiosperms

(= Carpel)

The FlowerThe Flower

Perianth: Sepals & petals collectively Androecium: stamens collectively Gynoecium: pistils collectively

Types of FlowersTypes of Flowers

Complete flower: has all 4 floral parts Incomplete flowers: missing a floral part(s) Perfect Flower: bisexual Imperfect flower: unisexual flowers

Staminate flowers: have only the stamens Pistillate (carpellate) flowers: have only pistils

Monoecious plants: separate staminate and pistillate flowers on the same plant

Dioecious plants: either staminate or pistillate flowers

Floral symmetry: Actinomorphic flower: floral parts are of similar shape &

size (radially symmetrical) Zygomorphic: floral parts are different (bilaterally

symmetrical) Inflorescence: A cluster of flowers with a definite

arrangement Fertilization: the fusion of two gamete nuclei to produce a

diploid zygote Pollination: transfer of pollen from the anther to the stigma

Pollen transferred within the same flower is called self-pollination, and the species is an in-breeder

Pollen transferred to a different flower is called cross-pollination and the species is out-breeder

Example of Example of Monocot Monocot Flower: Flower:

Lilium sp.Lilium sp.

Example of Monocot Flower: Example of Monocot Flower: Lilium sp.Lilium sp.

DicotDicot

Example of a Dicot FlowerHibiscus moscheutosHibiscus moscheutos

DicotDicotStamens

Stigmas

Hibiscus IIHibiscus II Style

Filament tube

Ovary

Ovules

Angiosperm Life Angiosperm Life CycleCycle

Fertilization

Microspores

Zygote

Sperm Egg

Sporophyte

Megaspores

Pollen

Micr

ogam

etoge

nesis

Meg

agam

etoge

nesis

Meiosis

Embryo sac

1n2n

Micosporogenesis

Megasporogenesis

Development of PollenDevelopment of Pollen

Microsporogenesis: the development of microspore mother cell (microsporocyte) into microspores This involves meiosis

Liliy FlowerLiliy Flower

MicrosporocytesMicrosporocytes

Microsporocyte undergo MeiosisMicrosporocyte undergo Meiosis

Tetrads of MicrosporesTetrads of Microspores

4 microspores were produced by meiosis Microsporogenesis is complete

Microspores

Pollen tetrads

Development of PollenDevelopment of Pollen

Microgametogenesis: the development of microspores into male gametophyte (pollen grain)This involves mitosis

Mature Male Mature Male gametophytegametophyte

Microspores underwent mitosis to produce male gametophytes

Mature Pollen grainMature Pollen grain

Tube nucleus

The tube nucleus produced the pollen tube

The generative cell produced two sperm nuclei

Development of Female Development of Female GametophyteGametophyte

Megasporogenesis: the megasporocyte (megaspore mother cell) develops into megaspores by meiosis

LiliumLilium Ovary Ovary

Megasporocyte Before MeiosisMegasporocyte Before Meiosis

Megasporocyte

Two-nucleate Stage Two-nucleate Stage (formed by meiosis)(formed by meiosis)

Four-nucleate Stage Four-nucleate Stage (formed by meiosis)(formed by meiosis)

This survives others die

Functional Functional MegasporeMegaspore

Megasporogenesis is complete

Development of Female Development of Female GametophyteGametophyte

Megagametogenesis: the megaspore develops into mature female gametophyte (embryo sac) by mitosis

Three mitotic divisions follow

First mitotic Division: First mitotic Division: 2-nucleate embryo sac2-nucleate embryo sac

22ndnd Mitotic Division: Mitotic Division: 4-Nucleate embryo sac4-Nucleate embryo sac

33rdrd Mitotic Division: Mitotic Division:8-Nucleate embryo sac8-Nucleate embryo sac

8-Nucleate embryo sac8-Nucleate embryo sac

Egg & 2 synergids

2 of 4 Antipodals

Pollination & Pollination & FertilizationFertilization Pollen Tube

Sperms

Double FertilizationDouble Fertilization