Angiosperms (Lect. 19)

When is a pollen grain released from the microsporocyte?

It may be released BEFORE OR AFTER the generative cell nucleus divides.

What happens to the ovary wall as it develops into a fruit?

It thickens and becomes differentiated into distinct layers.

What is the microsporocyte?

mother cell of microspores

What is a cotyledon?

part of the embryo within the seed of a plant that may become the embryonic first leaves of a seedling; this is also a characteristic used to classify angiosperms.

What is another name for the carpel?

pistil

How many species of Angiosperms are there?

240,000 - 300,000

What special structure found in bryophytes and some vascular plants in which a single egg is produced is not present in Angiosperms?

Archegonium

Define and describe the sepal. What is the name for a group of sepals on a flower?

One of the outermost flower structures; covers and protects the flower parts when the flower is a bud; there to protect the flower; they are green. A group of them on a flower are called the calyx.

What is the receptacle?

enlarged or elongated stem axis to which floral parts are attached; the part of the axis of a flower stalk that bears the floral organs

How many cotyledons do Monocots have?

1

How many cotyledons do Dicots have?

2

Where does the pollen tube land and what does it do?

It lands on the stigma of the carpel and goes down the style to ONE particular ovule

What provides the initial stored food for the embryo?

The endosperm

What is the world's largest flower and what kind of plant is it?

A Rafflesia arnoldii (also called a corpse flower because it smells very strongly of decaying flesh), and it is a Holoparasite (contains just a bud and a flower). *There are some plants with larger flowering organs, but those are technically clusters of many flowers, not just one flower.*

Describe the development of the male gametophyte.

A cell from the microsporocyte undergoes MEIOSIS twice and becomes a tetrad with 4 haploid cells which are microspores. Then each microspore under goes MITOSIS and becomes a 2-celled pollen grain with one tube cell and one generative cell. This is an IMMATURE microgametophyte. Once the generative cell's nucleus divides, there are 2 sperm cells and a tube cell; this makes a 3-celled MATURE microgametophyte.

Define and describe the petals. What is the name for a group of petals on a flower?

A flower part that is generally, but not always, conspicuously colored; plays and important role in attracting animal pollinators. Petals together on a flower are called the corolla.

What does the zygote develop into?

An embryo

What special structure that sperm are produced in in other plants do Angiosperms not have?

Antheridium

What Phylum are Angiosperms in?

Anthophyta. Also called, magnoliophyta.

What are the results of the fusion of the male and female gametes?

Double fertilization where one of the fertilizations produces a diploid (2n) zygote and one of the fertilizations produces a triploid (3n) nucleus which is the result of a triple fusion.

Describe the development of the female gametophyte.

Each ovule starts with a megasporocyte in the ovule chamber which is surrounded by integument which is surrounded by the megasporangium. There is an opening in the megasporangium called the micropyle. The megasporocyte undergoes MEIOSIS twice and becomes 1 functional megaspore and 3 "other" megaspores that disintegrate. The functional megaspore then undergoes MEIOSIS 3 times to create 8 different cells (goes from 1 -> 2 -> 4 -> 8). There are 3 antipodal cells against the wall of the embryonic sac at the opposite pole from the egg. There are 2 synergid cells which are against the wall next to the egg cell at the opposite pole from the antipodals. There is an egg cell and there are 2 polar nuclei with in the 1 central cell. *Therefore the embryonic sac contains 8 nuclei within 7 cells.* All of these cells in the embryonic sac makes up the MATURE megagametophyte.

Mature, ripened ovaries are what?

Fruits

What is another term for fertilization and does it happen before or after pollination?

Fusion of gametes, which occurs after pollination has already happened.

Define and describe the stamen of a flower. What is the name for all the stamen on a flower make up?

Has the structures that hold the pollen-bearing anthers; consists of a filament (which is the long stalk of a stamen) attached to an anther (where pollen grains are produced) at the end; this is the male reproductive unit of a flower. The floral whorl that comprises all the stamen on a flower is called an Androecium.

Habits of Angiosperms:

Herbs, Grasses, Shrubs, Trees, Aquatic plants, Herbaceous vines, Woody vines (lianas), Epiphytes, Parasites (Hemiparasites and Holoparasites)

What develops into a seed coat

Integuments

What role in fertilization do Stamen play?

It contains the pollen in a flower, but does not do anything for the actual fertilization process. A stamens purpose is to help get the pollen to another plants ovary but holding it high up and making it available to be taken to another plant.

What role in fertilization do Carpels play?

It contains the stigma which helps get the pollen by being a receptive surface. The pollen grain germinates into a pollen tube when it reaches the stigma. The pollen tube, which contains the two sperm cells and the tube nucleus, grows through the style, then through the micropyle, and into the ovule chamber. One sperm fuses with an egg, which is in the ovule, and becomes a zygote. The ovary is where the fusion of the sperm and egg occurs.

Define and describe the carpel of a flower. What is the name for the aggregate of carpels on a flower?

It is a vessel consists of the stigma (the receptive surface for the pollen grains; it is also where the pollen grains germinate), the style (a slender column of tissue that arises from the top of the ovary and through which the pollen tube grows), the ovary (the enlarged basal portion of a carpel or gynoecium composed of fused carpels; when mature it is a fruit), and the ovule(s)[there can be one or more] (a structure in seed plants containing the female gametophyte with the egg cell, all being surrounded by the nucellus and one or two integuments; when mature it is a seed). The entire carpel vessel is called the gynoecium.

Describe what happens in the anthers.

It is(or holds) the microsporangia (a hollow structure where the microspores are produced) and it makes pollen; In the anthers, meiosis produces microspores that develops into a male gametophyte, also called microgametophytes, which is pollen.

After creation, what does the endosperm do?

Provides essential food materials for the embryo and maybe also the young seedling

Mature ovules, enclosed within fruits are what?

Seeds

Name the different whorls/spirals of parts of a flower and if they are sterile or fertile.

Sepals(sterile), Petals(sterile), Stamen(fertile), and Carpels(fertile).

Where do pollen grains start and where are they transferred to?

Start on the anther and are transferred to the stigma.

What part of a flower has the potential to develop into a fruit?

The ovary develops into the fruit wall, specifically the ovary wall and other related structures develop into fruit.

What part of a flower has the potential to develop into a seed?

The ovules.

What is double fertilization?

The simultaneous fertilization when one sperm fuses with one egg to become a zygote; one sperm fuses with the central cell that contains two polar nuclei

What is the size range in Angiosperms?

The size range is very large, from less then 1 mm to more then 110 meters.

What role in fertilization do Petals play?

They are sterile.

What role in fertilization do Sepals play?

They are sterile.

What role in pollination do Petals play?

They attract animal pollinators to the flower. This is a very important role.

What role in pollination do Stamen play?

They contain the pollen in flowers. They are composed of a filament (long, thin structure) that holds the anther, which is where the pollen grains are produced.

What role in pollination do Carpels play?

They contain the stigma, style, and ovary, which contains the ovule. Pollen must get to the stigma, which is the receptive surface for the pollen. From the stigma, the pollen grain enters the style and the pollen tube begins to develops all the way down the style to the micropyle, which is the entrance to the ovary. The pollen grain is now in the ovule chamber.

What do synergid cells do?

They help attract the pollen tube. One of them dies before fertilization even occurs

What do antipodal cells do?

They sometimes play a part in embryo nutrition.

What role in pollination do Sepals play?

They support the flower.

Once pollen grains are transfered from ther anther to the stigma, what happens?

They take up water from cells of the stigma surface and germinate, forming a pollen tube.

What is triple fusion?

When one sperm fuses with the central cell containing two polar nuclei to become the endosperm nucleus, which is triploid (3n) and provides food for the growing embryo.

Pollen Grain: what is it composed of and what are their purposes?

develops into two cells: one, the generative cell, divides to produce the two sperm cells; the other, which is the tube cell, produces the pollen tube through which sperm travel to the ovary, the tube nucleus is the cell that leads the two sperm cells to the ovule chamber. The pollen grain has an outer layer to protect the sperm while they travel from the anther to the stigma.

What does the embryo develop into?

hypocotyles and cotyledons

What are Hemiparasites and what is an example of one?

is a type of plant that can photosynthesis on its own, but gets water and minerals from its host cell. An example is mistletoe.

What are Holoparasites and what is an example of one?

is a type of plant that gets its water, minerals AND carbohydrates from its host plant. It could not exist without its host plant. They do not have chlorophyll, so they cannot do photosynthesis. Some examples are dodder plants, beech drops, Indian pipes, and pine sap.

What is another name for a germinated pollen grain?

mature microgametophyte

What is the hypocotyl?

the stem of a germinating seedling

What kind of variety is in pollen grains and what do they help do?

they vary A LOT in size and shape. They are helpful for determining plant composition from plants from a long time ago; They allow you to identify species or even genus

What do germinated pollen grain consist of?

tube nucleus and 2 sperm cells