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Reproduction in flowering plants

Reproduction in flowering plants. Differences between gymnosperms and angiosperms in reproductive structures. Ovule. Seed cones and pollen cones. Evolution of the flower. A stem ( receptacle ) developed with 4 whorls of leaves tightly clustered at the end.

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Reproduction in flowering plants

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  1. Reproduction in flowering plants

  2. Differences between gymnosperms and angiosperms in reproductive structures Ovule Seed cones and pollen cones

  3. Evolution of the flower • A stem (receptacle) developed with 4 whorls of leaves tightly clustered at the end. • 1. Outside leaves are protective (sepals) • 2. Inside this are leaves which are usually developed for attraction (petals) • 3. Inside these are the male sporophylls (Stamens composed of anther and filament) • 4. Innermost leaves are the female sporophylls (carpels)

  4. Evolution of the carpel TOP Leaf folds over Edges of the leaf meet and fuse Open leaf with ovules at the edges Section

  5. Flower variations • Monoecious e.g. maize - separate male and female flowers on the same plant (c.f. conifers) • Dioecious e.g. holly - separate male and female plants

  6. Wind not scented petals small and inconspicuous nectaries poorly developed Vectored scented petals large and coloured well developed nectaries Wind versus vectored pollination

  7. Ovule development Megaspore (n) divides mitotically 3 times to give 8 nuclei: 3 antipodal cells 2 polar nuclei Egg with 2 synergids

  8. Microspore (n) divides to give 2 nuclei. One of these (vegetative nucleus) looks after the house-keeping functions. The other (generative nucleus) divides to give 2 sperm nuclei. Pollen development

  9. Pollen lands on the stigma (pollination) where it germinates. It sends out a pollen tube down the style into the ovary where it is attracted to the micropyle of an ovule. 2 nuclei are released, one to fertilise the egg (fertilisation), one to combine with the 2 polar nuclei. This gives a triploid tissue, the endosperm which acts as a storage reserve in the seed. Pollination and fertilisation

  10. Embryo development ‘Torpedo- shaped, embryo Division to give embryo and suspensor Testa (seed coat) ‘Heart shaped’ embryo ‘Globular embryo’ Cotyledons Shoot apex Hilium (scar where the ovule was attached to the ovary) Root apex Suspensor Micropyle

  11. Simple fruits are formed from one or fused ovaries Peach 3 carpels fused at their edges e.g. Tomato Pea pod Apple - ovaries are overgrown by a fleshy receptacle

  12. Aggregate fruits are formed from separate ovaries from one flower Blackberry Strawberry

  13. Runners e.g. strawberry Rhizomes e.g. violet Tubers e.g potato Root suckers e.g. apple Grafting Cuttings Micropropagation Above ground horizontal stems Below ground horizontal stems swollen underground stems shoots formed from roots Asexual reproduction (vegetative propagation)

  14. 2 cotyledons expand to form ‘seed leaves’ Hypogeal- hypocotyl elongates Above ground Germination Epicotyl Seed Below Ground Hypocotyl Seed just about to grow out Epigeal- epicotyl elongates

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