Plants

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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
      • 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
        • Cross-Pollination leads to cross-fertilisation
          • Outbreeding more important evolutionary
            • Because different genotypes are required for natural selection to occur
        • 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
    • 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
      • Carpel/Pistil
        • Ovary
          • Contains one or more ovules which contain the female gametes
        • Style
          • Stalk like structure
        • Stigma
          • surface which receives the pollen
      • Receptacle
        • Apex of the flower stalk, bearing the flower parts
    • 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
      • Seed Structure
        • Monocotyledons
          • seeds containing one cotyledon
            • surrounded by food reserve
          • typical of cereal grains
        • Dicotyledons
          • seeds containing two cotyledons
            • Contain food reserve within them
          • broad bean
        • 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
    • 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
      • 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

Comments

music1996

Meant to have the title "Plant Reproduction" but don't know how to change titles...

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