38 Angiosperm Reproduction and Biotechnology Flashcards
What are the unique features of angiosperm reproduction?
Flowers, fruits and double fertilisation.
What feature of plant reproductive cycle is not seen in animals?
Alternation of generations in which the plants have diploid stages and haploid states that alternate.
What is the diploid stage of alternation of generations called?
The sporophyte
What is the haploid stage of alternation of generations called?
The gametophye
What can the parts of a flower be broken down into?
The female reproductive organs, the male reproductive organs and the supporting structures.
What are the female reproductive organs of a plant collectively called?
The Carpel
What does the carpel include?
The Ovary which is at the centre of the flower. A ’style’ grows up from the ovary and ends with a ‘stigma’
What are the male reproductive organs collectively called?
The stamen.
What does the stamen include?
Around the ovaries are multiple stamens. Each includes a ‘filament’ that holds up the ‘anther’
What is inside each ovary?
One or more ovules.
What do the supporting structure of a flower include?
A receptacle, sepal and petal.
What is the petal?
A large, typically coloured, tissue that attracts insects.
What are sepals?
Small leaflike (but not leaves) flaps at the bottom of the flower. They enclose the flower when it is still developing i.e. they form the bud.
What are receptacles?
The structure at the base of the flower that connects it the stem. (similar to the petiole found in a leaf)
What are the basic types of flowers?
‘Complete flowers’ and ‘incomplete flowers’.
How do complete and incomplete flowers differ?
Complete flowers have all 4 basic flower organs (sepals, petals, stamens and carpel).
Incomplete flowers lack one or more of these structures.
What can incomplete flowers further be grouped as?
Sterile (no-reproducitve organ), unisexual (stamen or carpel) and fertile (stamen and carpel)
How can flowers be arranged?
On their own or in large groups called ‘inflorescences’
What is an example of an inflorescence?
A sun flower. This is because each of those brown structures in the central disk is a separate ‘incomplete flower’
What is the basic life cycle of angiosperms? (hint: focus on alternation of generations)
Male gametophyte (pollen grain) alands on the stigma. It forms a ‘pollen tube’ and thus fertilises the female gametophyte (‘embryo sac’)
This ‘fertilisation’ leads to a ‘diploid sporophyte’ (‘embryo’). A fruit develops from the embryo causing the release of seeds.
These seeds develop in to ‘mature sporophytes’ which then release ‘male gametophytes’ as pollen whilst also maintaining female gametophytes (‘embryo sac’) in the ovaries.
What is the female gametophyte of angiosperms?
Embryo sac.
What is the male gametophyte of angiosperms?
Pollen grains.
What is a carpel also known as?
A ‘pistil’ (note that this can also refer to multiple fused carpels.)
How are male gametophytes formed?
Each anther contains four ‘microsporangia’ or ‘pollen sacs.’ Each microsporangium contains diploid ‘microsporocytes’ (‘microspore mother cells’)
Each microsporocyte divides by meiosis to form 4 ‘microspore.’ Each ‘microspore’ grows by mitosis to form a pollen grain.
Each pollen grain contains a ‘generative cell’ (haploid) that will become two sperm. To also includes a ’tube cell’ that will later form the pollen tube.
What is the ploidy of the microsporocyte?
Diploid
What is the ploidy of the microspores?
Haploid
What is the ploidy of the ‘generative cell’ in the pollen grain?
Haploid
What is the ploidy of the ‘tube cell’ in the pollen grain?
Haploid
What is it called when the pollen grain develops the pollen tube?
Germination i.e. “the pollen grain has germinated to form a pollen tube.”
What is the structure of a pollen grain?
It contains a tough wall called the ’spore wall’ surrounds a ’tube cell’ and a ‘generative cell’
By the time the pollen grain has developed the ‘generative cell’ will actually be inside the ’tube cell’!
The spore wall may contain spikes i.e. in an animal pollinated species.
What forms the ’spore wall’ of the pollen grain?
It is composed of materials produced by the microspore and by the anther.
What happens when the pollen grain lands on the stigma?
It ‘germinates’ as the ‘tube cell’ forms a large protuberance called a ‘pollen tube’ which grows down the style.
As the pollen tube grows down the style the generative cell which is inside the ’tube cell’ divides into two sperm cells.
As the pollen tube reaches the ovary it releases the two sperm into the ovule
What is the female gametophyte called?
‘Embryo sacs’
What is the structure of a ovule?
It consists of a ring composed of ‘megasporangium. (n). Inside this is large diploid cell called the ‘megasporocyte’ (‘megaspore mother cell’).
At the base of the ovule are two ‘integuments’ which are diploid sporophytic tissue that completely surrounds the ovule except for a ‘microphyle’ at the bottom.
What do the ‘integuments’ of the ovule develop into?
The seed coat
What structure does the ovule eventually become?
A seed
What structure does the ovary eventually become?
The ovule.
What happens during female gametophyte development?
The megasporocyte (‘ megaspore mother cell’) enlarges and undergoes meiosis, producing four haploid megaspores. Only one megaspore survives; the others degenerate.
The nucleus of the surviving megaspore divides by mitosis three times without cytokinesis, resulting in one large cell with eight haploid nuclei. The multinucleate mass is partitioned by membranes into a multicellular female gametophyte—the embryo sac.
What happens the the 8 haploid nuclei of the megaspore?
3 become ‘antipodal cells’, 2 become ‘polar nuclei’, 2 become ’synergies’ and 1 becomes an ‘egg’
What is the ploidy of the ‘megasporangium’?
Diploid
What is the ploidy of the ‘megaporocytes’?
Diploid
What is the ploidy of the ‘integuments’?
Diploid
What is the ploidy of the ‘megaspore’?
Haploid
What is the ploidy of the ‘antipodal cells’?
Haploid
What is the ploidy of the ‘polar nuclei’?
Haploid
What is the ploidy of the ‘egg’ in an ovule?
Haploid
What is the ploidy of the ‘synergids’?
Haploid
What is the structure of a complete ovule?
At the bottom is has an opening called the ‘microphyle’. The ‘integuments’ completely surround the ovule except at the microphyle.
At the entrance of the microphyle is a single egg. It is surrounded by two ’synergids’: one on each side.
At the centre of the ovule is two ‘polar nuclei’.
At the far end (relative to the microphyle) of the ovule are three ‘antipodal cells’
What are the ’synergies’ of the ovule?
Cells that flank the egg at the microphyle. They help attract and guide the pollen tube to the embryo sac.
What are the ’polar nuclei’ of the ovule?
Cells at the centre of the ovule that will develop into endosperm
What are the ’antipodal cells’ of the ovule?
Their function has not yet been determined.
What are the basic “vectors” of pollination?
Wind, Bees, Moths/Butterflies, Flies, Bats and Bees.
What is wind pollination also known as?
‘Abiotic pollination’ as it is the only format that does not depend on ‘biotic factors’ i.e. animals. (another extremely rare form of abiotic pollination by water is found in a select few species)
How does the shape of wind pollinated flowers help collect pollen?
They are shaped so that in the wind they generate ‘eddy currents’ that suck the pollen in.
What determines what type of cell each of the 8 nuclei of the megaspore will develop into?
A gradient of auxin concentration which is released from the microphyle.
What carries pollen in ‘abiotic pollination’?
Most commonly the wind but in a few species water carries the pollen.
What are some typical feature of bee-pollinated flowers?
They have bright petals that glow when seen under ultraviolet light. They often also have a sweet fragrance.
They are typically yellow or blue as red seem dull to bees.
There are four flowers: one red, one blue, one yellow and one grey. Predict the likely pollinator for each?
Red: Birds
Blue: Bees
Yellow: Bees or Birds
Grey: Moths
What are some typical feature of towers pollinated by butterflies and moths?
Butterflies and moths are both able to smell and thus the flower will likely be scented.
Moths are nocturnal so the flowers they pollinate will likely be grey. Butterflies are active in the day so will pollinate brightly coloured flowers
What are some typical feature of fly-pollinated flowers?
They will often have a odour like rotten meat. They may also be red like meets.
What is a ‘carrion’ flower?
A specific flower that is pollinated by flies and thus produces an odour like rooting meats.
What are some typical feature of bird pollinated flowers?
They are often red or yellow but since birds do not have a developed sense of smell they are not scented.
Many have petals that are fused to formed a long tube that the bird must insert its beak into and thus ensures it rubs against the anthers and the stigma.
At the end of the tube there is often a sweet sugary substance called nectar.
What is it called when two species evolve together i.e. so that they can be symbiotic?
‘Coevolution’
What is an example of coevolution?
Darwin observed a madagascan orchid with a long tube. He deduced that their must an organism with a tongue long enough to reach into it. This was confirmed with the observation of such as moth.
