Angiosperm Reproduction

Question 1

What is the male reproductive part of a angiosperm flower? the female organ?

Answer 1

staMEN - male Carpel - female

Question 2

What are the different parts of the stamen (microsporophyll)?

Answer 2

Anther - contain the microsporangia that produce pollen

Filament - the stalk that holds up the anther

Question 3

What are the different parts of a carpel (megasporophyll)?

Answer 3

Stigma - “sticky stigma” captures pollen.

style - Long slender neck that connects stigma to ovary

ovary - at the base of the style, contains ovules which become seeds if fertilized

Question 4

What is the difference between a complete and incomplete flower?

Answer 4

Complete flowers have all 4 flower structures (sament, capel, sepal, petal)

Question 5

What is the difference between a sporophyte generation and a gametophyte generation in an angiosperm?

Answer 5

Sporophyre generations are the parts that we can see, gametophyte genrations are microscopic and we cant see them.

Question 6

What are inflorescences?

Answer 6

This is a type of incomplete flower where an incomplete disk composed of hundreds of incmplete flowers are surrounded by sterile incomplete flowers that look like yellow petals.

Question 7

What is the difference between a simple pistil and a compound pistil? What about stigmas?

Answer 7

A simple pistil has one unfused carpel or can be multiple unfused carpelsnext to each other.

Compound pistils are multiple carpels that are fused together with either one stigma for all or multiple stigmas (one for each fused carpel).

Question 8

What are the two methods of pollination and some examples of them?

Answer 8

Abiotic - pollenation by wind, wind pollenators tend to release large amounts of pollen

Biotic - For example, bees, moths, bats, and flies. Tend to attract pollenators via nectors, scents, and colors.

Question 9

What is the difference between pollination and fertilization?

Answer 9

Pollenation - pollen sticks to stigma

Fertilization - sperm fertilizes egg

Question 10

Look at the life cycle of the angiosperm and be able to track it. Understand these terms:

gametophyte development, pollination, double fertilization, seed development

Answer 10

DO IT NOW

Question 11

What is an ovary? What do they contain?

Answer 11

This is the part of the carpel that contains ovules with a multicellular megasporangium.

Question 12

How are megaspores (n) formed within the megasporangium (2n)?

Answer 12

One cell in the megasporangium called the megasporocyte undergoes meiosis which makes four of them, only one megaspore (n) survives, however.

Question 13

With the one surviving megaspore in an angiosperm, describe how it becomes a embryo sac (female gametophyte).

Answer 13

The megaspore divides by mitosis 3 times w/o undergoing cytokinesis, making a large cell with eight different nuclei.

This mass is then divided by membranes to form an embryo sac

Question 14

What are the four different parts of an embryo sac, their function, and how many cells make up each?

Answer 14

Antipodal cells (3) - unknown function

polar nuclei (1, 2 nuclei)

Synergids (2) - guide pollen tube to embryo sac

Egg (1)

Question 15

What is an anther? What do they contain?

Answer 15

An anther is the part of the stamen that contain the microsporangia, each anther has 4 microsporangia. the microsporangia house many microsporocytes (2n).

Question 16

Describe how a male angiosperm gametophyte is formed.

Answer 16

Many microsporocytes (2n) within a microsporangia undergo meiosis to from 4 haploid microspores (n). Each microspore undergoes mitosis to form a haploid male gametophyte (n) consisting of 2 cells: a generative cell and a tube cell, this is contained in a spore wall and the collective unit is called a pollen grain.

Question 17

How is the male gametophyte delivered to the female gametophyte in an angiosperm?

Answer 17

The microsporangium breaks open and releases pollen, the pollen that attaches to the stigma of a carpel (pollenation). The pollen grain then germinates by absorbing water which make the tube cell create a pollen tube that travels down the style of the carpel to deliver the sperm to the female gametophyte.

There are two sperm traveling down the pollen tube with the tube nucleus leading the pack as it travels towards the mircophyle, the synergid cells are releasing chemicals that attract the tube to the microphyle. Once a passageway is formed from the tube to the embryo sac the two sperm are discarded in the vacinity of the female gametophyte.

Question 18

What is double fertilization in angiosperms? Why is this important?

Answer 18

Fertilization happens once the two sperm reach the female gametophye. one fertilizes the eggto form the zygote (2n), the other fertilizes the two polar nuclei to form a triploid (3n) nucleus which will give rise to the endorsperm.

Double fertilization ensures that the endosperm only devleops where the egg has been fertilized, so as to not waste resources

Question 19

What comes first, embryo development or endosperm development?

Answer 19

Endorsperm development usually comes first

Question 20

What is the function of the endorsperm?

Answer 20

To store nutrients that can be used by the seedling, sometimes these nutrients are exported to the cotyledon before the seed development completes, sometimes not.

Question 21

In the development of the embryo (2nd stage of seed development), what does the first split of the zygote produce and what are the functions of these things? What are the cotyledons?

Answer 21

The basal cell and the terminal cell the result of the first split of the zygote.

Basal cell - produces multicellular suspensor that anchors embryo to parent plant.

Terminal cell - gives rise to most of the embryo.

Cotyledons - these are the embryonic leaves in the seed, usually two of them so it gives embryo a heart shape.

Question 22

Describe the final maturation of the seed and the strucutre of the mature seed in a EUDITCOT. What is the hypocotyl and epicotyl? Plumule?

How do some seeds of eudicots differ from monocots?

Answer 22

The seed dehydrates until only 5%-15% of weight is water. Embryo is surround by food supply (either the cotyledon or the endosperm)

hypocotyl - the embryonic axis below the cotyledons, terminates in the radicle (embryonic root)

Epicodyl - region above the cotyledon

Plumule is composed of the epicotyl, young leaves, and shoot apical meristem.

SOME EUDITCOTS HAVE TWO COTYLEDONS

THINK OF GARDEN BEAN

Question 23

Describe the mature structure of the seed of a MONOCOT. What is a scutellum? What are the two sheaths that protect the monocot embryo?

Answer 23

MONOCOTS HAVE ONLY ONE COTYLEDON

Scutellum - specialized cotyledon that has a large surface area (latin for shield) found in monocots.

coleoptile - covers the young shoot and aids in soil penetration

coleorhiza - covers the young root and aids in soil penetration

THINK OF MAIZE

Question 24

Describe the dormancy phase of a seed, what is the advantage of this?

What is required to break the seed out of dormancy?

How long does seed dormancy last?

Answer 24

This is the stage where a seed stops growing and its metabolism all but ceases, also seed is dehydrated till 5%-15% of weight is water

The advantage of this is to ensure that the seed will germinate only when the conditions are right

specific environmental cues like temperature or light changes, sometimes just a favorable environment

Dormancy can last centuries, years, or days. Depends on the seed.

Question 25

What is the thing that initiates germination of a seed?

Answer 25

Imbibition - the uptake of water by the seed due to its low water potential.

Question 26

Describe the process of seed germination in a eudicot.

Answer 26

Radicle emerges first to develop the root system and anchor the plant.

In eudicots the hypocotyl forms a hook and the hook is pushed above the ground with the cotyledon shoot tip on the end

Light then straightens the hook and the cotyledon shoot tip points up

Question 27

Describe the process of seed germination in a monocot.

Answer 27

Radicle emerges and develops roots that anchor the plant.

Cleoptile (shoot sheath) pushes up through the soil and creates a tunnel for shoot tip to grow through.

Question 28

After germination, what type of growth do plants undergo? Where does this growth occur and how is it possible?

Answer 28

Vegetative growth

stems, leaves, and roots

Photosynthesis

Question 29

What happens first, vegetative or reproductive growth?

Answer 29

Vegetative

Question 30

Why do flowers of a given species occur at a specific time of year?

Answer 30

To promote outbreeding

Question 31

What is a fruit? What is its purpose?

Answer 31

This is the mature ovary of a flower

It protects the seeds and aids in dispersal by wind or by animals.

Question 32

What is the pericarp?

Answer 32

This is the thickened wall of a fruit derived from the ovary wall

Someitmes the wall of ovary can dry out at maturity like in soybeans but in grapes they can remain more fleshy

Question 33

What are the four different types of fruit, their description and an example?

Answer 33

SImple - develop from a single or several fused carpels (pea fruit)

Aggregate - single flower with multiple separate carpels that form small fruitlets that cluster together. (raspberry)

Multiple - develop from group of flowers tightly clustered together called an inflorescence, the ovary walls fuse together into one fruit (pineapple fruit)

Accessory - contain other floral parts in addition to ovaries, such as an apple that has a fleshy receptacle, the ovary is located at the core.

Question 34

What are the 3 ways that seeds can be dispersed and some examples of each?

Answer 34

Water - buoyant seeds and fruits (coconut has embryo and endosperm within hard endocarp layer that is covered by a buoyant husk)

Wind - maple seeds have wings to help them travel by wind, tumble weeds tumble across terrain while scattering their seeds, dandelion fruits

Animals - squirrels hide seeds underground in stashes that they may forget about, some have sharp spines that are dispersed when discarded after piercing something or someone, some edible fruits are eaten and dispersed through species, ants carry seeds to their underground nest

Question 35

What are some modes of asexual reproduction of angiosperms (4)?

Answer 35

Fragmentation - This is when separated parts of a parent plant develop into whole plants.

Some plants root systems give rise to adventitious roots that become a separate shoot system. Aspen trees do this

Apomixis - the asexual production of seeds from a diploid cell (dandelions)

Parthenocarpy - the asexual reproduction of fruit.

Question 36

What are some advantages and disadvantages of sexual and asexual reproduction in angiosperms?

Answer 36

Asexual - successful survival in a stable environment is an advantage while clones of the plant are vulnerable to extinction with environmental changes

Sexual - genetic variation makes evolutionary adaptation possible, while a disadvantage is only a fraction of seedling survive

Question 37

What is vegetative reproduction another name for?

Answer 37

asexual reproduction because vegetative fragments are what give arise to the progeny.

Question 38

Can some flowers self-fertilize to ensure every ovule becomes a seed?

Answer 38

YES

Question 39

Why would flowers want to make it impossible to self-fertilize?

Answer 39

This helps to ensure genetic diversity because parent plants would always be different.

Question 40

What are some ways that a angiosperm prevents selfing (self fertilization)?

Answer 40

Dioecious - separate plants have the male and female gametophytes

Some plants have stamens and carpels that mature at different times

Some have a genetic component that creates a self-incompatibility so they cant self-fertilize, this can be in the form of a plant rejecting pollen with a s-gene with a matching allele to the stigma cells, this leads to a block in the formation of a pollen tube