Angiosperm Reproduction Flashcards
What is the male reproductive part of a angiosperm flower? the female organ?
staMEN - male Carpel - female
What are the different parts of the stamen (microsporophyll)?
Anther - contain the microsporangia that produce pollen
Filament - the stalk that holds up the anther
What are the different parts of a carpel (megasporophyll)?
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
What is the difference between a complete and incomplete flower?
Complete flowers have all 4 flower structures (sament, capel, sepal, petal)
What is the difference between a sporophyte generation and a gametophyte generation in an angiosperm?
Sporophyre generations are the parts that we can see, gametophyte genrations are microscopic and we cant see them.
What are inflorescences?
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.
What is the difference between a simple pistil and a compound pistil? What about stigmas?
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).
What are the two methods of pollination and some examples of them?
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.
What is the difference between pollination and fertilization?
Pollenation - pollen sticks to stigma
Fertilization - sperm fertilizes egg
Look at the life cycle of the angiosperm and be able to track it. Understand these terms:
gametophyte development, pollination, double fertilization, seed development
DO IT NOW
What is an ovary? What do they contain?
This is the part of the carpel that contains ovules with a multicellular megasporangium.
How are megaspores (n) formed within the megasporangium (2n)?
One cell in the megasporangium called the megasporocyte undergoes meiosis which makes four of them, only one megaspore (n) survives, however.
With the one surviving megaspore in an angiosperm, describe how it becomes a embryo sac (female gametophyte).
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
What are the four different parts of an embryo sac, their function, and how many cells make up each?
Antipodal cells (3) - unknown function
polar nuclei (1, 2 nuclei)
Synergids (2) - guide pollen tube to embryo sac
Egg (1)
What is an anther? What do they contain?
An anther is the part of the stamen that contain the microsporangia, each anther has 4 microsporangia. the microsporangia house many microsporocytes (2n).
Describe how a male angiosperm gametophyte is formed.
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.
How is the male gametophyte delivered to the female gametophyte in an angiosperm?
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.
What is double fertilization in angiosperms? Why is this important?
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
What comes first, embryo development or endosperm development?
Endorsperm development usually comes first
What is the function of the endorsperm?
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.
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?
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.
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?
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
Describe the mature structure of the seed of a MONOCOT. What is a scutellum? What are the two sheaths that protect the monocot embryo?
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
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?
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.
What is the thing that initiates germination of a seed?
Imbibition - the uptake of water by the seed due to its low water potential.
Describe the process of seed germination in a eudicot.
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
Describe the process of seed germination in a monocot.
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.
After germination, what type of growth do plants undergo? Where does this growth occur and how is it possible?
Vegetative growth
stems, leaves, and roots
Photosynthesis
What happens first, vegetative or reproductive growth?
Vegetative
Why do flowers of a given species occur at a specific time of year?
To promote outbreeding
What is a fruit? What is its purpose?
This is the mature ovary of a flower
It protects the seeds and aids in dispersal by wind or by animals.
What is the pericarp?
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
What are the four different types of fruit, their description and an example?
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.
What are the 3 ways that seeds can be dispersed and some examples of each?
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
What are some modes of asexual reproduction of angiosperms (4)?
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.
What are some advantages and disadvantages of sexual and asexual reproduction in angiosperms?
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
What is vegetative reproduction another name for?
asexual reproduction because vegetative fragments are what give arise to the progeny.
Can some flowers self-fertilize to ensure every ovule becomes a seed?
YES
Why would flowers want to make it impossible to self-fertilize?
This helps to ensure genetic diversity because parent plants would always be different.
What are some ways that a angiosperm prevents selfing (self fertilization)?
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
