D3.1 plant reproduction

Define flowering plants/ angiosperms

A large category (phylum) in the plant kingdom that have flowers as their reproductive structures. Plants can have either male or female reproductive structures or both

Define stigma

sticky tip of the carpel where pollen will enter through

define petal

brightly coloured modified leaves to attract insects/ pollinators

define style

tube connecting stigma to ovule

define ovule

egg cells (female gamete) and is the site of fertilization where embryo and developing seed are housed in and is contained in ovaries

define anther

organ producing pollen (male gamete)

define filament

stalk supporting anther

define sepal

outer layer to protect bud of developing flower

define pistil/ carpel and what parts of the plant is in it

it is the female parts of the flower (stigma, style, ovule)

what is the stamen

the male parts of the flower (anther, filament)

where are female gametes and male gametes produced?

female gametes are produced inside ovules and male gametes are produced in the pollen grain (gametes are produced through the process of meiosis)

define pollination

transfer of pollen from anther to stigma

how is pollen transferred

Pollen can be carried by wind or pollinators (insects, birds, small mammals). Pollinators feed on nectar produced by the flower, pollen grains may attach to their legs/ wings/ back/ body and transfer to stigma of same or diff. flower as the pollinator moves around

what does the pollen grain do after reaching the stigma?

Pollem gain elongates and germinates to form a pollen tube which extends down the style into the ovary. Male gamete is transported down the pollen tube.

What are the two forms of pollination?

Self-pollination and cross-pollination

self pollination: transfer of pollen to stigma of the same hermaphroditic plant

cross-pollination: transfer of pollen from one plant to stigma of a different plant of the same species

explain why pollination is a form of sexual reproduction

• Gametes are produced through meiosis

• fertilization is the fusion of gametes to form a zygote

• cross-pollination increases genetic diversity

what are some method of pollen transfer

1) via animals

• transfer of pollen via animals such as bats, insects and birds

• flowers can be brightly coloured, rich with nectar or emit a sweet smell

2) wind

• many flowers of grasses and cereal crops are pollinated by wind

• flowers are usually small, unscented and do not have nectar (usually a dull appearance)

what are some mechanisms that promote cross-pollination and prevent self-pollination

RECALL! many flowers are hermaphrodites (contain both the female and male reproductive parts)

self fertilization will naturally produce offspring that will show less variation than their parents in comparison to those that are a result of fertilization from two gametes of different individuals

• several mechanisms prevent self-fertilization in hermaphrodite flowers

• anthers and stigma are separated from each other to prevent self-pollination

• stamens (with pollen) and stigmas may mature at different times

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

define self-incompatibility mechanisms

• self-pollination involves breeding between close relatives

• individuals will resemble their relatives genetically (the variability of genes is reduces)

• self-incompatibility is often defined as the inability of hermaphroditic flowers to produce zygotes after self-pollination

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

  • genes may be present that are incompatible with each other (e.g. the aloe plant can recognise its own pollen and does not allow fertilization to occur)

where does fertilization happen?

It occurs in the ovule

what is the process of fertilization?

Fertilization occurs when male gamete fuses with the female gamete in the ovule. Zygote forms and develops into embryo within a seed

what is the dispersal of seeds

seed dispersal is the carrying of the seed away from the vicinity of the parent plant.

why does dispersal of seeds need to occur?

it needs to occur or else the seed will compete with the parent plant for resources. Seeds may be dispersed by wind, water or animals

what are the three ways that wind is dispersed and how?

1) wind

• light with adaptations such as wings or hair (e.g. dandelion and maple)

2) water

• seeds are buoyant

• specialised structures or husks help the seeds float e.g. coconut, water lilies

  • coconuts can move up to 10m from the parent plant just by bouncing and rolling after falling to the ground from a height of 10-20 m

  • they can survive up to 120 days afloat on the sea

3) animals

• seeds are often covered by fruit which animals may eat and then discard the seeds elsewhere

• seeds may be consumed with the fruit and then deposited in the faeces some distance away

• some animals store/hide them over the winter months

• some adaptations like hooks and spines allow seeds to hitch a ride on passing animals

• burrs and velcro

what is consisted in the seed structure?

• seed coat: formed from the ovule wall

• hilum: scar where it used to be attached to the ovary/ fruit

• radicle: embryo root

• hypocotyl: embryo stem

• epicotyl: embryo leaves

• cotyledon: food (starch) storage tissue

what are the required conditions for germination

1) water

• seeds absorb water through the micropyle

  • causes the cotyledons to secrete plant growth substances

• seeds dry out for dispersal

  • at germination all cells need to rehydrate so that metabolic reactions can occur

2) oxygen

• energy is used in many of the metabolic events in germination

• energy is produced by aerobic respiration n

3) warmth

• metabolic events in germination require enzymes

  • sensitive to temp (temp is often used as a trigger for germination)

  • e.g. many seeds from temp climates only germinate after being exposed to cold temperatures for several days before the warmer temperatures

  • this results in germination in spring

• ideally 25-30 c

define germination

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

• begins with the uptake of water and is complete when the radicle emerges from the seed

what is the procedure of the germination of a plant?

• it begins with the uptake of water

• is complete when the radicle emerges from the seed

• stored food in the seed is used to drive this process

• germination will only occur when the conditions are ideal (otherwise it remains dormant, where metabolic activities have slowed down)

• dormancy period vary from plant to plant

outline the procedure of the development into a seedling

• rapid growth results in the primary root (radicle) emerging → marks the end of germination

• the plumule/shoot appears

• plant is now referred to as a shoot

• light plays an important part in how the seedling oriented themselves

• the plumule emerges in a hook like state in order to protect the delicate growing tip