B9-B10 (plant Tropism + Reproduction) Flashcards
What is tropism?
Growth movement in response to stimulus
Towards stimulus -> positive
Away from stimulus -> negative
What are the stimulus, response and pos/neg response for photo/gravi/hydro tropism?
Phototropism:
Stimulus-> direction of sunlight
Pos response-> shoots grow towards the light
Neg response-> roots grow into the ground
Gravitropism:
Stimulus-> directions of gravitational force
Pos response-> roots growing down (with force of gravity)
Neg response-> shoot growing up (against the force of gravity)
Hydrotropism:
Stimulus-> direction of a water source
Response-> roots grow towards the water source
What is auxin?
Auxin is (multiple) plant hormone that speeds up growth in the shoot and slows growth in the root
Produced at the tip of the shoot
What is the role of auxin in phototropism?
Auxin diffuses to the shaded side of the shoot
Light from above -> auxin and light is evenly distributed -> growth is straight
Light from an angle -> auxin is diffused to shaded side -> cells on shaded side elongate (grows quicker) -> uneven growth -> shoot curves towards the sun
What role does auxin play in gravitropism?
Auxin is diffused to the lower side of the plant
Shoot -> auxin seeds growth -> shoot curves up
Root -> auxin slows growth -> roots curve down
Label and explain the structure of a flower (reproductive)
Stigma
Sticky pad for pollen to stick to
Style
Holds and elevates the stigma
Ovary
Produces ovules (female gamete)
Nectary
Produces and contains nectar
Sepal
Leftover from protecting the flower during development
Petal
Attracts pollinators via color
Filament
Holds and elevates anther (makes it easier to spread pollen)
Anther
Contains and produces pollen
Carpel
Stigma, style, ovary -> female reproductive system
Stamen
Filament, anther -> male reproductive system
Receptacle
Peduncle
What is pollination?
Pollen moving (either by wind or pollinators) to a different plant of the same species to fertilise
The transfer of pollen from the anther -> stigma
Label and explain the structure of a wind-pollinated flower (reproductive)
Petal
Small and dull in color
No need to attract pollinators
Anthers
Exposed to the wind
Easy to blow away
Stigma
Feathery for more surface area to catch the pollen
No nectary
No scent or nectar -> no need to attract pollinators and takes too much energy
What are the difference between wind and pollinator pollinated flowers?
Pollen grain
Wind -> small, light, easy to carry
Pollinator -> big, spiky, stick to pollinators
Stigma
Wind -> feathery
Pollinators -> sticky
Nectary
Wind -> no nectary
Pollinator -> nectar and scent (bird pollinated -> no scent)
Anther
Wind -> exposed to wind
Pollinator -> exposed so pollen can easily stick
Petal
Wind -> dull and small
Pollinator -> big and colorful
What is self pollination?
Pollen of the plant fertilises itself
What is cross pollination?
Pollen from one plant fertilizes another plant
Why is cross pollination more preferable?
Creates variety
Increases adaptation
Survival of the species
How is self pollination prevented?
Separate male and female plants
Different lengths of stigma and anther
Stamen and stigma mature at different times
-> impossible to self pollinate
->first stamen then stigma
Describe the process of plant fertilization and the formation of a pollen tube
Pollen tube formed from pollen grain
-> pollen lands on tube
-> chemical signals from style and stigma
-> pollen grain grows a tube from cell wall
-> male gamete travels through tube (cytoplasm)
Goes through style -> ovary -> ovule -> nucleus fuse = fertilisation
Note: pollen tubes can only be produced if it is a flower of the same species (hormones are specific)
What do the ovules and ovary become after fertilisation?
Ovule -> seeds
Ovary -> fruit
