Lecture 8 Angiosperms

Angiosperms

Seed plants with reproductive organs in flowers and seeds enclosed in fruits

Synapomorphies of angiosperms

-Xylem contains vessels

-Net venation in leaves

-Flowers and fruits

-Ovules in carpel

-Germination of pollen on stigma

-Double fertilization

-Endosperm

Flower

Shoot with modified leaves

All flower parts are…

modified leaves.

Sepals

-Collectively, calyx

-Protection and attraction

Petals

-Collectively, corolla

-Protection and attraction

Stamen

Bears male microsporangia

Ovules and seeds are enclosed in…

a carpel

Pistil

One or more fused carpels, containing the ovaries, style, and stigma

Pollination

Movement of pollen from anther to stigma

Angiosperm life cycle

-Megaspore undergoes three rounds of mitosis without cytokinesis (1 cell with 8 nuclei)

-Reorganization into 7-celled megagametophyte with two polar nuclei

-Microspore → 2-cell pollen grain (one generative cell and one tube cell)

-Generative cell divides to produce two sperm

-Tube cell divides to produce pollen tube to ovule

-One sperm cell fuses with egg to form 2n zygote

-One sperm cell fuses with polar nuclei to form 3n cell (endosperm)

Zygote develops into an embryo with one or two ___.

cotyledons

Cotelydons

Can absorb or digest the endosperm and/or enlarge to become photosynthetic when the seed germinates

Tissues in angiosperm seeds

-Embryo (2n)

-Nutritive endosperm (3n)

-Seed coat (2n) (from sporophyte)

What is the function of synergids?

Attract pollen tubes

I and III

7-celled structure with 8 nuclei

Megagametophyte