9.4 Reproduction in plants Flashcards
What are the three ways a plant can reproduce?
Vegetative propagation
Spore formations
Pollen transfer
What is vegetative propagation?
Asexual reproduction from a plant cutting
What does the sexual reproduction in flowering plants involve the transfer of?
Pollen to an ova
What are the three distinct phases of sexual reproduction in flowers?
Pollination
Fertilisation
Seed dispersal
What is pollination?
The transfer of pollen grains from an anther to a stigma
Why can many plants self pollinate?
Many plants possess both male and female structures
What is the most preferred pollination and why?
Cross pollination as it improves genetic diversity
What is fertilisation?
The fusion of a male gamete nuclei with a female gamete nuclei to form a zygote
Where is the female gamete found?
In the ovule
Where is the male gamete found?
In the pollen grain
What does the fertilisation of gametes result in?
The formation of a seed
What happens to the seed once it has been formed?
It moves away from the parental plant
What does seed dispersal reduce?
Competition for resources between the germinating seed and the parental plant
What are different seed dispersal mechanisms?
Wind
Water
Fruits
Animals
What does seed structure depend on?
The mechanism of dispersal employed by the plant
What is cross pollination?
Cross pollination involves transferring pollen grains from one plant to the ovule of a different plant
What is the most common way to transfer pollen?
By animals
What are animals that transfer pollen called?
Pollinators
What type of relationship are pollinators in with the flowering plant?
A mutualistic relationship
What is a mutualistic relationship?
Where both species benefit from the interaction
What do flowering plants gain from the mutualistic relationship?
A means of sexual reproduction via the transfer of pollen between plants
What do animals gain from a mutualistic relationship with the flowering plant?
A source of nutrition
Why are pollinators attracted to plants?
Because they secrete sugar rich nectar
What are examples of pollinators?
Birds
Bats
Insects
What are flowers structured to do?
Optimise access for certain pollinators
What are flowers?
The reproductive organs of angiospermophytes
Where do flowers develop from?
The shoot apex
When talking about flowering, what do changes in gene expression trigger?
The enlargement of the shoot apical meristem
What does the shoot apical meristem then differentiate into?
Sepals
Petals
Stamen
Pistil
What influences the activation of genes responsible for flowering?
Abiotic factors that are typically linked to the seasons
When will flowering plants typically come into bloom?
When a suitable pollinator is most abundant
What is the most common trigger for a change in gene expression?
Day/night length (photoperiodism)
What is it called when a flower has both male and female structures?
Monoecious
What is it called when a flower only possesses one sex structure?
Dioecious
What is the male part of the flower called?
Stamen
What is the stamen composed of?
Anther and filament
What is an anther?
Pollen producing organ of the flower
What is pollen?
The female gamete of a flowering plant
What is a filament?
Slender stalk supporting the anther
What does the filament do?
Makes the anther accessible to pollinators
What is the female part of the flower called?
The pistil/carpel
What is the pistil composed of?
Stigma
Style
Ovule
What is the stigma?
The sticky, receptive tip of the pistil that is responsible for catching the pollen
What is a style?
The tube shaped connection between the stigma and ovule
What does the style do?
Elevates the stigma to help catch pollen
What is the ovule?
The structure that contains the female reproductive cells
What happens to the ovule after fertilisation?
It will develop into a seed
What are other structures plants have alongside reproductive structures?
Petals
Sepal
Peduncle
What are petals?
Brightly coloured modified leaves which function to attract pollinators
What are sepals?
Outer covering which protects the flower when in bud
What is a peduncle?
Stalk of the flower
What is the purpose of flowering?
To enable the plant to sexually reproduce
What are phytochromes?
Phytochromes are leaf pigments which are used by the plant to detect periods of light and darkness
What is photoperiodism?
The response of the plant to the relative lengths of light and darkness
What are the two forms phytochromes exist in?
Active form and inactive form
What is the inactive form of phytochromes converted into and when?
The active form when it absorbs red light
What is the active form of phytochrome broken down into and when?
It is broken down into the inactive form when it absorbs far red light
When will the active form revert to the inactive form?
In the absence of light
When is the inactive form predominant and why?
During the night as the active form is reverted in darkness
What can only the active form of phytochrome do and when does it differ?
Cause flowering
It differs in certain types of plants
What are the two categories plants can be classed as?
Short day or long day plants
What is the critical factor in determining the activity of plants?
Night length
When do short day plants flower?
When the days are short
What do short day plants require?
The night period to exceed a critical length and low levels of Pfr
What does Pfr inhibit in short day plants?
Flowering
When do long day plants flower?
When the days are long
What do long day plants require?
The night period to be less than a critical length and high levels of Pfr
What activates flowering in long day plants?
Pfr
What does the mnemonic SID the LAD tell us?
Short Day plants pfr Inhibits flowering
Long Day plants pfr Activates flowering
How can the flowering of short day and long day plants be manipulated?
By controlling the exposure of light
What must happen to the the critical night length for it to be effective?
It must be uninterrupted
When will long day plants traditionally not flower and why?
During winter and autumn because night lengths are long
When do horticulturalists expose long day plants to light source to trigger flowering?
During the night
What are an example of long day plant?
Carnations
When will short day plants traditionally not flower and why?
During summer months because the night lengths are short
How can horticulturalists trigger flowering in short day plants?
By covering the plant with an opaque black cover for roughly 12 hours a day
What happens once a seed is dispersed from the parental plant?
It will germinate resulting in a new plant
What does a typical seed contain?
Testa
Micropyle
Cotyledon
Plumule
Radicle
What is the testa?
An outer seed coat that protects the embryonic plant
What is the micropyle?
A small pore in the outer covering of the seed that allows for the passage of water
What is the cotyledon?
Contains the food stores for the seed and forms the embryonic leaves
What is the plumule?
The embryonic shoot
What is the plumule also called?
The epicotyl
What is the radicle?
The embryonic root
What is germination?
Germination is the process by which a seed emerges from a period of dormancy and begins to sprout
What are the four thing germination needs to occur?
Oxygen
Water
Temperature
Optimal pH
Why does germination need oxygen
For aerobic respiration
For the seed to develop what does it need?
Large amounts of ATP
Why does germination need water?
To metabolically activate the seed
What does the metabolic activation of the seed trigger?
The synthesis of gibberellin
Why does germination need temperature?
They need certain temperatures to sprout and for the optimal function of enzymes
Why does germination need an optimal pH?
Seeds require a suitable soil pH in order to sprout and for the optimal function of enzymes
What are five different specialised conditions for germination?
Fire
Freezing
Digestion
Washing
Scarification
Why does germination potentially need fire?
Some seeds will only sprout after exposure to intense hear
Why does germination potentially need freezing?
Some seeds will only sprout after periods of intense cold
Why does germination potentially need digestion?
Some seeds need animal digestion to erode the seed coat before the seed will sprout
Why does germination potentially need washing?
Some seeds may be covered with inhibitors and will only sprout after being washed to remove the inhibitors
Why does germination potentially need scarification?
Seeds are more likely to germinate if the seed coat is weakened from physical damage
How can germination be measured?
By the rate of seed growth over a set period of time
What is an example of fire affecting germination?
After bushfires remove established flora
What is an example of freezing affecting germination?
In spring following winter temperatures
