D3.1 PLANT REPRODUCTION

draw the structure of a hermaphroditic flower

outine the structures in a flower and its functions

stamen (male part flower)

• anther: pollen producing organ of the flower (male gamete)

• filament: slender stalk, supporting the anther (making it more accessible to pollinators)

pistil (female part flower)

• stigma: sticky, receptive tip of pistil, responsible for catching pollen

• style: tube shaped connection between stigma and ovule

• ovule: structure inside the ovary containing the female reproductive cells

other structures

• petal: bright, coloured leaves to attract pollinators

• sepals: outer cover which protects flower when in bud

• receptacle: supportive base for other flower structures

outine the process of sexual reproduction in flowering plants through pollination which leads to fertilisation

• female gametes produces inside ovules, male gametes in the pollen grain

• pollination which is the transfer of pollen from an anther to the stigma must occur for the male gamete to fertilize the female gamete

  • pollen can be carried by the wind or pollinators

POLLINATION:

• when a pollen grain interacts with the stigma, it elongates and germinates to form a pollen tube which extends down the style into the ovary

  • male gamete transported down the pollen tube to reach female gamete

FERTILISATION:

• when the male gamete fuses with the female gamete in the ovule, it forms a zygote which goes through mitosis to develop into an embryo within a seed

methods of pollination

• self pollination: transfer of pollen from anther to stigma of the same plant

• cross pollination: transfer of pollen from one plant to another plant stigma of the same species

  • increases genetic diversity

methods of pollen transfer

POLLINATORS

• pollen can be transfered via pollinators, aka animals (bats, birds, insects)

• flowers contain brightly coloured flowers and are rich with nectar which may emit a sweet smell → these factors attract pollinators

• pollinators feed on nectar produced by the flower and pollen grains may attach to their body and transfer to the same of different stigma on another flower when they move around, allowing for pollination

WIND

• some plants may not have factors to attract pollinators and are pollinated by wind

• wind carries pollen grains from the stamen on one flower to the stigma of another

• these plants typically produce large quantities of small pollen grains to increase chance of pollination

outline self-incompatibility mechanisms to increase genetic variation within a species

• self fertilisation will produce an offpsring that will show less genetic variation

  • to avoid this….

    • anthers and stigma are separated from each other

    • stamen and stigmas may mature at different times

    • male and female reproductive parts may appear in different flowers or on different plants

• if this doesnt work then dis will happen (imagine this is like 2nd line of defence)

  • self-incomaptibility mechanisms: inability of flowers to produce zygotes after self pollination

    • failure may occur during pollen germination, growth of pollen tube, fertilisation or embryo development

methods of seed dispersal

seed dispersal is the carrying of the seed away from the vicinity of the parents plant which must occur or else the seed will compete with the parent plant for resources

1. wind

• light adaptations such as wings or hair

2. water

• seeds are buoyant

• have specialised structures or husks to help the seed float on water

3. animals

• seeds are often covered by fruit which animals consume then discarded in the feces some distance away from its origin

• some seeds may have adaptations such as hooks, spines which allow seeds to attach/latch onto a passing animal

draw a seed

outilne the structure of a seed and outline its functions

seed coat: formed over ovule wall

micropyle: pore that allows water absorption

radicle: embryo root

hypocotyl: embryo stem

epicotyl: embryo leaves

cotyledon: food storage tissue

what is germination and outline the steps to germinate a seed

• germination is the resumption of growth by an embryonic plant in seed or fruit

  • this will only occur when the conditions are ideal, otherwise it will remain dormant

• steps

  • uptake of water through the micropyle

  • activation of hormones and enzymes

  • breakdown of stach to maltose in cotyledons

  • transport of maltose to embryo

  • maltose used to build structures and to provide energy for aerobic respiration to produce ATP

    • germination is complete when a radicle emerges from the seed

outline the steps from a seed to a seedling

• radicle emerges from the seed, marking the end of germination

• plumule appears, now reffered to as seedlilng