9.4 - Reproduction in Plants Flashcards
Flowering involves a change in gene expression in the shoot apex
1) Compare the vegetative and reproductive phases of the angiospermatophyta life cycle
2) state that flowers are produced from a shoot apical meristem
3) State two abiotic factors that may trigger flowering
4) Compare the timing of flowering in short-day plants and long-day plants
5) Outline the process by which changes in gene expression trigger fowering
Vegetative structures include roots, stems and leaves = develop in young plants
Flower = allow plant to sexually reproduce - reproductive shoot
Temperature and day length can transform a leaf producing shoot into a flower producing shoot - amount of light which a flower recieves plays a role of either inhibitors or activators of genes that control flowering.
In long day plants - active form of phytochrome pigment leads to transcription of a gene that controls flowering (FT gene). The FT mRNA is transported to the shoot apical meristem in the phloem where is it translated into the FT protein - turn on flowering genes
The switch to flowering is a response to the length of light and dark periods in many plants
1) state the role of the pigment phytochrome
2) describe the conversions between the two forms
3) describe the role of phytochrome in controlling flowering in long and short day plants
photoperiodism is a biological response to a change in the proportions of light and dark in 24 hour cycle.
control of flowering achieved by a process called photoperiodism - critical factor is not day length but night length
1) flowering in long day and short day plants is controlled by the plants biological clock
2) the length of the darkness/night if the critical factor
short days = long night (winter)
long days = short nights (summer)
Photochromes:
- combination of a protein and pigment molecule
- can change its shape (active site) : will change the way chemicals around it react to it – can change into 2 different shapes
- Blue / green plant pigments that are produced in the leaf
- present in low concentration
- is a combination of protein molecule + pigment molecules
- is able to absorb light of a certain wavelength and change its structure / form
- p (r) absorb mainly red light
- p (fr) absorbs mainly far red light
Plants use phytochromes to measure the length dark period / critical period
- during the day (presence of light), P(r) converts to P (fr)
- during the night P (fr) converts to P(r)
active form stimulates some growth and inhibits other growth
Success in plant reproduction depends on pollination, fertilisation and seed dispersal
1) define pollination, fertilisation and seed dispersal
2) state the changes to the ovule and ovary that result from fertilisation
3) List mechanism of seed dispersal
Plants can reproduce in a number of different ways
1) vegetative propagation
2) spore formations
3) pollen transfer
sexual reproduction in flowering plants involves the transfer of pollen (male ) to an ova (female)
Pollination - the process in plants in which pollen grains are transferred to the female gametes, enabling fertilisation and sexual reproduction
Fertilisation - fusion of male and female gametes to produce a diploid zygote - in flowering plants a double fertilisation occurs producing the embryo and the endosperm nucleus
Seed dispersal - movement or transport of seeds away from the parent plant - decreased competition between parents and offspring and promotes diversity within the species
flowering plants use mutualistic relationships with pollinators in sexual reproduction
1) define mutualism
2) explain an example of mutualism between a flowering plant and its pollinator
pollination - act of transferring pollen grains from the male anther of a flower to the female stigma - goal of every living organism including plants is to create offspring for the next generation - making seeds is an example
- mutualism is relationship between two organisms, where both organism benefit
- sexual reproduction depends on the transfer of pollen stamen from one plant to the stigma of another plant
- pollen can be transferred by wind and possibly water but more commonly pollen is transferred by animals known as pollinators such as bees, butterflies, birds and bats
- Pollinators gain food from nectar and the plant gains a method to transfer pollen to another plant to allow sexual reproduction
Methods used to induce short-day plants to flower out of season
1) state how plants can be manipulated to force flowering out of season
Horticulturalists can manipulate the flowering of short-day and long-day plants by controlling the exposure of light - make changed to lengths of night or day.
Flowering can be controlled by : greenhouses and light conditions
Short day plants : dark during daylight - give bursts of far red light , keep Pfr low so flowering not inhibited
Long day plants : artificially lit during night , short bursts of light using red light can interrupt darkness and promote flowering
Drawing internal structure of seeds
1) Draw and label the structure of seeds including : Embryo root, Embryo shoot, Cotyledons, Testa, Micropyle and Hilum
2) State the function of the different parts of the seeds
Seed coat, Epicotyl, Hypocotyl, Cotyledons, Radicle
Drawing of half-views of animal pollinated flowers
1) Draw and Label an animal pollinated flower including - Nectar secreting glands, Petals, Sepals, Anthers, Filaments, Carpel, Stigma, Style, Ovary and Ovule
Pistil, Stigma, Style, Ovary
Stamen, Anther, Filament
Petal
Ovule with Embryo sac
sepal
receptacle
peduncle
Design of experiments to test hypotheses about factors affecting germination
1) defining germination
2) Outline why water, oxygen and warmth required for germination
3) Outline the role of gibberellin during germination
4) write five example problems, questions for experiments that could test factors affecting germination
- Pick a type of seed
- Vary one factor for investigation
- Mention how you will keep other factors constant
- How results will be collected and how it will be decided if a plant germinated or not
Germination Process
seeds need water for germination - water rehydrates the seed’s tissues causing the cells to expand and metabolism to become reactivated - once metabolism has been reactivated embryonic growth can begin
Oxygen needed for aerobic respiration to take place in the seed
1) water is absorbed by the seed through the micropyle and the seed coat
2) water causes the release of a hormone called gibberellin
3) GA causes the cells to expand and elongate eventually allowing the root to break through the seed coat
4) GA also stimulates the production of enzyme that hydrolyze starch located in the seed’s endosperm into maltose
5) Maltose is further broken down into glucose which can be transported to areas of growth in the cell
6) glucose is used in aerobic respiration to produce energy of the embryonic root and shoot
