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Angiosperm Reproduction and Biotechnology Chapter 38 p. 771-780.

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Presentation on theme: "Angiosperm Reproduction and Biotechnology Chapter 38 p. 771-780."— Presentation transcript:

1 Angiosperm Reproduction and Biotechnology Chapter 38 p. 771-780

2 LE 38-2b Haploid (n) Diploid (2n) Key Simplified angiosperm life cycle Germinating seed Seed Simple fruit Embryo (2n) (sporophyte) Zygote (2n) FERTILIZATION Egg (n) Sperm (n) Embryo sac (n) (female gametophyte) Ovule Ovary Germinated pollen grain (n) (male gametophyte) Pollen tube Anther Mature sporophyte plant (2n)

3 Flower Structure  Flowers are the reproductive shoots of the angiosperm sporophyte Stamen: (“male parts”)  Anther: where pollen is produced  Filament: supports anther Carpal: (“female parts”)  Ovary: contains ovules (hold female gametophytes)  Stigma: where pollen lands  Style: encloses ovary & supports the stigma Time Lapse of Flowering Plant Life Cycle Flower Blooming (time lapse)

4 LE 38-2a Stamen Anther Filament An idealized flower Receptacle Petal Carpel Sepal Ovary Style Stigma Haploid (n) Diploid (2n) Key

5 Flower Variations  Many flower variations have evolved during the 140 million years of angiosperm history A) Symmetry: radial/bilateral B) Ovary Location: superior/semi- inferior/inferior C) Floral Distribution: individual flowers/inflourescence (clusters) D) Reproductive Variations:  Monoecious: stamen & carpal on same flower  Dioecious: stamen & carpal on different plants


7 Gametophyte Development and Pollination  Pollination is the transfer of pollen from an anther to a stigma Pollen grain produces a pollen tube that grows down into the ovary and discharges sperm near the embryo sac  Pollen develops from microspores within the sporangia of anthers  Embryo sacs develop megaspores w/in ovules  Bat Pollinating Agave Plant Bat Pollinating Agave Plant  Bee Pollinating Bee Pollinating

8 LE 38-4 Development of a male gametophyte (pollen grain) Pollen sac (microsporangium) Micro- sporocyte Micro- spores (4) Generative cell (will form 2 sperm) Each of 4 microspores Male gametophyte (pollen grain) Nucleus of tube cell MITOSIS (LM) 75 µm Ragweed pollen grain (colorized SEM) 20 µm Key to labels Haploid (n) Diploid (2n) MEIOSIS Development of a female gametophyte (embryo sac) Mega- sporangium Ovule Embryo sac Female gametophyte (embryo sac) Mega- sporocyte Integuments Surviving megaspore Micropyle Ovule Antipodal cells (3) Polar nuclei (2) Egg (1) Synergids (2) Integuments (LM) 100 µm

9 Double Fertilization  The pollen tube discharges TWO sperm into the embryo sac One sperm fertilizes the egg The other combines with the polar nuclei of the embryo, giving rise to the food-storing endosperm

10 From Ovule to Seed  After double fertilization, each ovule develops into a seed  The ovary develops into a fruit enclosing the seed(s)  Endosperm Development: Stores nutrients that can be used by the seedling OR Exports its food reserves to the cotyledons

11 Embryo Development  The first mitotic division of the zygote, splits it into a basal cell and a terminal cell Terminal cell → embryo Basal Cell → Suspensor → anchors & transports nutrients to embryo

12 Structure of the Eudicot Seed  1) Seed Coat: hard, protective shell that encloses embryo & provides food supply  2) Radicle: embryonic root  3) Embryonic Axis Hypocotyl: below cotyledon attachment Epicotyl: above cotyledon attachment  Contains shoot tip & 2 mini leaves  4) Cotyledon: “meat” of seed; stores food

13 Structure of Monocot Seed  Scutellum: thin, specialized cotyledon that absorbs nutrients during germination  Coleoptile: covers young shoot  Coleorhiza: covers young root

14 From Ovary to Fruit  A fruit develops from the ovary Protects enclosed seeds and aids in seed dispersal by wind or animals  Types: 1) Simple: derived from 1 carpal/several fused (i.e. peach, pea, nut) 2) Aggregate: results from single flower w/ 2+ carpals (i.e. raspberry) 3) Multiple: results from inflourescence (i.e. pineapple)

15 Developmental Origin of Fruits

16 Seed Germination  As a seed matures, it dehydrates and enters a phase called dormancy ↓ metabolic rate growth & development suspended  ↑ chances germination will occur at time & place most advantageous for seedling  Environmental cues required to break dormancy Change in temp or lighting

17 From Seed to Seedling  Germination depends on imbibition the uptake of water due to low water potential of the dry seed  1) Radicle (embryonic root) emerges first  2) Shoot tip breaks through soil surface  3) In many eudicots, a hook forms in the hypocotyl, and growth pushes the hook above ground  4) In maize & other grasses (monocots) coleoptile pushes up through soil

18 Seed Germination

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