Module 7

Micropyle

Tiny opening in the protective layers of an ovule

Integument

Protective outer layer of tissue around the inner parts of an ovule

Ovule

Contains the egg cell and develops into a seed after fertilization. A structure consisting of a megasporangium wrapped in protective tissue layers called integuments.

Whats the MAIN difference between an archegonia and an ovule?

Archegonium = egg-producing organ. Ovule = future seed.

Gymnosperms

“Naked seeds.” Pine trees, fir trees, cycads, and ginkgo.

Angiosperms

“Flowering plants, and enclose their seeds inside their fruits. Roses, apple trees, grasses

Describe the components of a seed for gymnosperms and angiosperms.

They both have seed coats (integument) and embryos. But the gymnosperm has archegonia still, while the angiosperm evolved to have an embryo sac. The gymnosperm feeds its embryo with the female gametophyte that forms AFTER pollicization, but in the angiosperm the female gametophyte is already there, instead, it has a central cell with 2 polar nuclei that after fertilization becomes a triploid becoming the endosperm that will feed the embryo that was ALSO born inside the embryotic sac inside the ovule.

Embryonic root

Radicle

Cotyledon

Embryonic seed leaves

Endosperm

Food tissue that nourishes the embryo in flowering plants.

Plumule

The developing shoot tip

Hypocotyl

The embryonic stem region below where the cotyledons attach

Epicotyl

The embryonic shoot region above where the cotyledons attach

How many cotyledons does a Eudicot have

2

How many cotyledons does a monocot have

1

Anthers

The pollen-producing, male reproductive part of a flower

Filament

The thread-like stalk that supports the pollen in the plant

Stamen

The male reproductive organ of a plant (Filament AND Anthers)

Pistil

Flower’s ovary

Sepal

A leaf located in the outermost part of the petals

Stigma

The sticky or waxy top part of a flower's female reproductive organ (the pistil or carpel) where pollen lands during pollination

Style

It guides the pollen tube down from the stigma to the ovary so fertilization can happen

Pericarp

Mature fruit wall

Mesocarp

The middle layer of a pericarp

Endocarp

The innermost layer directly surrounding the seed of a pericarp

Compare/contrast life cycles of gymnosperms & angiosperms (highlight differences in pollen, ovules, pollination, fertilization, dispersal).

In gymnosperms pollen is created INSIDE, and relies on wind for dispersal. For angiosperms pollen is made inside of its anthers, and rely on animals to TRANSFER pollen. The ovules for the gymnosperms sits outside, the ovules for the angiosperms are hidden inside the ovary. The female gametophyte in the Gymnosperm hasn’t developed before pollen arrives, and it takes a long time, while the Angiosperms make fertilization much more easier because the minute an animal comes, the female gametophyte is ready. For dispersal, mature seeds blow out to the wind, and for angiosperms the seeds are inside a fruit to get dispersed.

Fruit

A fruit is defined as a matured, ripened ovary of a flowering plant (angiosperm) that encloses and protects one or more fertilized ovules, which mature into seeds

What happened to archegonia in Angiosperm?

Because the angiosperm female gametophyte evolved to be microscopic (reduced to a 7-celled embryo sac), the distinct archegonium organ was lost entirely

Integuments

Seed Coat

How did flowers evolve? Describe the phylogeny of flowering plants.

They evolved from modified leaves called sporophylls (sporangia-bearing leaves) roughly 140 million years ago. Carpel evolved from megasporangia, stamens from microsporangia over time forming into a filament and anther. All ~250,000 living species of flowering plants belong to a single phylum, Anthophyta. The angiosperm evolutionary tree is based on; Basal angiosperms, early flowering plants, and core angiosperms is the VAST majority of flowering plants.

Anthophyta

The phylum of flowering plants

Carpel

The basic structural building block—an individual modified leaf (megasporophyll) that folded over to enclose the ovules

Describe mechanisms for pollination. What are strategies to avoid self-pollination?

Pollination from wind, water, and animals that get attracted by nectar. Plants make imperfect flowers to avoid self-pollination, or the male and female reproductive systems mature at different times.

Describe endosperm development. How does germination differ between monocots and eudicots?

The endosperm begins before the embryo development. In monocots the endosperms stays inside, in eudicots they are formed into 2 cotyledons. For eudicot the hypocotyl (the stem below the cotyledons) goes upward from the soil shielding the cotyledons from damage. For monocot leaves the coleoptile pushes straight up. For MONOCOTS the seed coat & cotyledons remain buried underground, for eudicots as the seedling goes up the cotyledons get dropped. In eudicots the endosperm nutrients go to the cotyledons, in monocots the endosperm nutrients don’t get tranferred.

Coleoptile

Pointy cone wrapped around a baby plant shoot

What are some mechanisms for asexual reproduction in plants?

Vegetative reproduction occurs when a parent plant breaks or divides into parts (fragmentation) that subsequently develop into whole, independent plants. Stolons, rhizomes, and tubers are examples. Apomixis (Asexual seed production).

What is the “ABC hypothesis” for flower reproduction?

• Class A gene activity alone —> Sepals

• Class A + B gene activity —> Petals.

• Class B + C gene activity —> Stamens.

• Whorl 4 (Innermost): Class C —> Carpels.

Apomoxis

Asexual seed reproduction

Aggregate fruit

A compound fruit derived from many separate ovaries within a single flower

Accessory fruit

A fruit where the main fleshy, edible portion develops from non-ovary flower tissues

Transgenes

A specific gene that has been taken from one species and artificially engineered into the genome of another species