Plants
- Created by: music1996
- Created on: 03-04-15 20:21
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- Plant Reproduction
- Pollination
- Pollination is the transfer of pollen grains from the anther to the stigma of a plant of the same species
- Self-Pollination
- The pollen from the anthers of a flower only are transferred to the stigma of the same flower or a different flower on the same plant
- Cross-Pollination
- Pollen is transferred from the anthers of one flower to the stigma on a flower on a different plant of the same species
- Types of pollination
- Wind pollinated
- Small, green inconspicuous flowers
- No scent
- No nectar
- Anthers hang outside flower
- So wind can blow pollen away
- Large feathery stigmas
- Providing large Surface Area to catch pollen grains
- Large quantities of small, smooth, light pollen
- Insect Pollinated
- Large, colourful petals
- Scent
- Nectar
- Anthers within the flower
- Stigma within flower
- Small quantities of sticky pollen
- Wind pollinated
- Genetic consequences of self and cross pollination
- Self-pollination leads to self-fertilisation (inbreeding)
- Depend on random assortment/crossing over during meiosis and mutation to generate variation in the genotypes of gametes
- Display less genetic variation
- Advantage is that offspring produced will be adapted to a stable environment
- Depend on random assortment/crossing over during meiosis and mutation to generate variation in the genotypes of gametes
- Cross-Pollination leads to cross-fertilisation
- Outbreeding more important evolutionary
- Because different genotypes are required for natural selection to occur
- Outbreeding more important evolutionary
- Mechanisms to ensure out-breeding
- Anthers and stigma mature at different times
- Anthers and stigma are at different levels in the flower
- Separate male and female flowers on different plants
- Self-pollination leads to self-fertilisation (inbreeding)
- Flower structure
- Sepals
- Protects the flower in bud
- Petals
- Brightly coloured
- Scented
- May produce nectar
- Corolla
- Acts as landing platform for insects
- Stamen
- Filament
- Long structure which supports the anther and contains phloem tissue to supply anther with sucrose and other organic molecules needed for pollen grain formation
- Anther
- produces polled grains which contains the male gametes
- Filament
- Carpel/Pistil
- Ovary
- Contains one or more ovules which contain the female gametes
- Style
- Stalk like structure
- Stigma
- surface which receives the pollen
- Ovary
- Receptacle
- Apex of the flower stalk, bearing the flower parts
- Sepals
- Fertilisation and seed development
- Fertilisation is the process whereby the male gamete fuses with the female gamete to produce a zygote
- pollen grain lands on stigma and starts to absorb water
- germinates to produce a pollen tube
- Pollen tube grows down the style secreting pectinase enzymes and digesting the tissues of the style
- Pollen tube enters ovule via the micropyle
- tip of pollen tube bursts releasing male gamete into embryo sac
- The male nucleus fuses with the female nucleus producing a zygote
- tip of pollen tube bursts releasing male gamete into embryo sac
- Pollen tube enters ovule via the micropyle
- Pollen tube grows down the style secreting pectinase enzymes and digesting the tissues of the style
- germinates to produce a pollen tube
- Seed Structure
- Monocotyledons
- seeds containing one cotyledon
- surrounded by food reserve
- typical of cereal grains
- seeds containing one cotyledon
- Dicotyledons
- seeds containing two cotyledons
- Contain food reserve within them
- broad bean
- seeds containing two cotyledons
- integuments become testa
- Micropyle remains
- fertilised ovule becomes seed
- Fertilised ovary becomes fruit
- plumule (embryo shoot)
- Radicle (embryo root)
- endosperm develops from embryo sac
- food reserve
- Monocotyledons
- Germination
- Requirements
- Water
- for mobilisation of enzymes
- cell vacuolation
- cell transport
- Temperature
- optimum temperatures for enzymes
- Oxygen
- aerobic respiration
- forms ATP
- required for metabolism and growth
- forms ATP
- aerobic respiration
- Water
- water absorbed by seed
- causing tissues to swell and mobilises enzymes
- testa ruptures
- radicle pushes through downwards
- plumule then pushes through upwards
- amylase enzyme hydrolyses starch into maltose
- transported to growing points
- cotyledons stay below ground
- plumule bent over in a hook to prevent soil abrasion to the tip
- plumule emerges from soil and unfurls and starts photosynthesising
- Cotyledon food reserves depleted
- plumule emerges from soil and unfurls and starts photosynthesising
- plumule bent over in a hook to prevent soil abrasion to the tip
- cotyledons stay below ground
- transported to growing points
- amylase enzyme hydrolyses starch into maltose
- plumule then pushes through upwards
- radicle pushes through downwards
- testa ruptures
- causing tissues to swell and mobilises enzymes
- Requirements
- Pollination
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