sexual reproduction in flowering plants b) pollination & fertilisation
TRANSCRIPT
Sexual Reproduction in Flowering Plants
b) Pollination & Fertilisation
Learning objectives• Define the terms: pollination, self-pollination• Outline methods of pollination including:
cross-pollination & self pollination• Define the term: fertilisation.• Outline seed structure & function of following:
testa, plumule, radicle, embryo, cotyledon • Explain embryo & food supply (endosperm or
seed leaves)• Classify plants as monocotyledon or
dicotyledon & distinguish between them.• Make reference to non-endospermic seed. 2
Sexual reproduction in flowers
Sexual reproduction in flowers
Can you answer the following from your JC Science
• Pollination involves the transfer of pollen from the _______________ to the __________________
• Self-pollination: _________________________ • Cross-pollination: ___________________________ Put these stages of sexual reproduction in order
(a) Germination(b) Seed and fruit formation (c) Pollination(d) Seed dispersal(e) Fertilisation
• http://www.youtube.com/watch?v=RuYrFwDuYn0&feature=fvw
Answer the questions on the following video
1. What method is used to transfer pollen in daffodils?Insect
2. What type of pollination occurs in daffodils?Cross
3. Name 1 feature found in flowers involved in insect pollinationLanding strips to guide insects into flower, nectar, colourful petals
4. Describe the appearance of the pollen of flowers involved in wind pollination
Smooth, produced in large amounts
5. What happens in some flowers if cross pollination doesn’t occursSelf pollination
6. How do plants prevent self fertilisationRelease chemicals that favours pollen from other plants
7. How do imperfect flowers prevent fertilisationMale and female parts are out of sync
Pollination
Pollination
Transfer of pollen from the anther to the stigma of a flower of the same species
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Pollination
Pollination
PollinationSelf pollination
• Transfer of pollen from an anther to a stigma of the same plant to form zygotes
Cross pollination• Transfer of pollen from
the anther to the stigma of a different plant of the same species to form zygotes. Most common. Cross pollination increases variation.
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Methods of pollination
• Insect Pollination
• Wind Pollination
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Pollination by Insects
What do flowers, that are involved in insect pollination look like? 1. Petals: Large & coloured2. Scented3. Nectaries to produce nectar4. Anthers and Stigmas inside the flower5. Pollen: Spikey E.g. : tulip, buttercup
Adaptations for wind pollination
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Pollination by Wind
What do flowers, that are involved in wind pollination look like? Petals: small and greenNo scentNo nectaries or nectarAnthers and feathery stigmas hanging outside the flowerPollen: Large amounts & smoothE.g.: grass, oak
Learning Check
1. What is pollination2. Name 2 types of pollination and explain each3. Name 2 methods of pollination4. For each method, explain the appearance of
the flower.
Fertilisation
Fertilisation
• Fertilisation is the fusion of the nuclei of the male (n) and female (n) gametes to produce a zygote (2n)
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Fertilisation
• The pollen grain produces the male gametes
• Embryo sac produces an egg cell and 2 polar nuclei
Polar nuclei
Embryo sac
Egg cell
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Stigma
Style
Ovary
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Embryo Sac
Polar nuclei
Egg Cell 21
Pollen Grain
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Pollen Tube
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Tube Nucleus
Generative Nucleus
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Tube nucleus disintegrates
Mitotic division of generative nucleus to form 2 male gametes
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One Male gamete fuses with the two polar nuclei to form the triploid endosperm nucleus
One male gamete fuses with the egg nucleus to form the diploid zygote
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3n Endosperm nucleus
2n Zygote
Double fertilisation
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Learning Check
1. What is fertilisation2. Name the 2 types of nuclei in the ovule that
are involved in fertilisation3. Explain the method of fertilisation in 3 steps4. What is double fertilisation
Sexual Reproduction in Flowering Plants
c) Seed Formation
Seed formation
Endospermic & Non-EndospermicMonocots & Dicots
3n Endosperm nucleus
2n Zygote
Seed Formation: A seed develops from a fertilised ovule
• The zygote grows repeatedly by mitosis to form an embryo
• Embryo: (part of seed that) becomes the new plant
• An embryo consists of a• plumule (shoot)
• a radical (root)
• cotyledons (food stores needed for germination)
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Seed Formation
• The endosperm nucleus (3N) divides repeatedly to form the endosperm in endospermic seeds. This endosperm acts as a food store for the developing seed
• e.g. maize
3n Endosperm nucleus
2n Zygote
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Seed Formation
• In non-endospermic seeds the endosperm is used up in the early stages of seed development so the food is stored in the cotyledons
• e.g. broad bean 3n Endosperm nucleus
2n Zygote
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EndospermFood store for developing embryo
EmbryoPlumule, radicle, cotyledons
Integuments, becomes the seed coat
Seed Formation
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If all the endosperm is absorbed by the developing embryo the seed is a non-endospermic seed e.g. broad bean
Seed Formation
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If all the endosperm is not absorbed by the developing embryo the seed is an endospermic seed e.g. Maize
Seed Formation
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Cotyledon:
- Seed leaf specialised for food storage. - Stores food such as starch and sugar
Testa:- Seed coat.
Seed types and structure
Seed
embryo
Plumule (immature shoot)
Radicle (immature root)
Cotyledon (food supply or seed leaf)
endosperm Food store
All seeds
In some seeds
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Endosperm
Seed coat (testa)
Cotyledon
Plumule – will develop into a new shoot
Radicle – will develop into a new root
Endospermic Seed e.g. Maize
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Endospermic seed: contains endosperm when fully developed
• Moncotyledons (one cotyledon)• Small, food is stored in the endosperm• Cotyledon absorbs food from endosperm and
passes it onto embryoE.g. Maize
Seed coat (testa)
Cotyledon
Plumule
Radicle
Non-Endospermic seed e.g. Broad Bean
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Non-endospermic seed: Has no endosperm when fully formed
• Dicotyledons (2 cotyledons)• Food is stored in the cotyledons• No longer has endosperm as it is used upE.g. broad beans
e.g. Broad Bean e.g. Maize
Plumule
Radicle
Cotyledon
Endosperm
Non–endospermic and Endospermic seed
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Classification of seedsClassified according to two features:1. Number of cotyledons (Seed leaves)
Monocotyledon Dicotyledon
2. Presence of endosperm Present – Endospermic Absent – Non-endospermic
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Broad Bean – Non-Endospermic DicotTesta 2 Cotyledons
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48Stems are herbaceous Stems can be herbaceous
or woody
Grass Barley
DaisyRose
Example of Monocot and Dicot
Monocot Dicot
Grass Buttercup
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Learning Check
1. What method of division occurs in a zygote to form the embryo
2. Name the 3 parts of the embryo3. What 2 ways are seeds classified4. Explain endospermic and non-endospermic5. Give an example of each of the above6. Name 3 features of a monocot and 3 features of
a dicot7. State 2 places food is stored in a seed?
Can you…….• Define the terms: pollination, self-pollination• Outline methods of pollination including:
cross-pollination & self pollination• Define the term: fertilisation.• Outline seed structure & function of following:
testa, plumule, radicle, embryo, cotyledon • Explain embryo & food supply (endosperm or
seed leaves)• Classify plants as monocotyledon or
dicotyledon & distinguish between them.• Make reference to non-endospermic seed. 53