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9.4 Reproduction in Angiospermophytes

9.4 Reproduction in Angiospermophytes. I. Flower Structure & Function. Flowers are the reproductive structure of plants (4 parts) 1. sepals 2. petals 3. stamens 4. carpels Flowering involves a change in gene expression in the shoot apex.

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9.4 Reproduction in Angiospermophytes

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  1. 9.4 Reproduction in Angiospermophytes

  2. I. Flower Structure & Function • Flowers are the reproductive structure of plants (4 parts) 1. sepals 2. petals 3. stamens 4. carpels Flowering involves a change in gene expression in the shoot apex. The switch to flowering is a response to the length of light and dark periods in many plants.

  3. B. All 4 floral parts are important but only stamens (“male” organs) and carpels (“female” organs) produce gametes C. A flower with all 4 parts is called “Complete”, if it doesn’t have all 4 parts it is called “incomplete” D. A flower with both stamens & carpels is said to be “perfect”, whereas an “imperfect” flower has one or the other but not both Complete flower

  4. E. Functions of flower parts

  5. Male & Female Flower Parts

  6. II. Pollination & Fertilization • Pollination: placement of pollen onto the stigma of a carpel by wind, water or animal carriers; a pre-requisite to fertilization 1. Self Pollination 2. Cross pollination

  7. B. Fertilization: the union of haploid gametes (pollen and egg) to produce a diploid gamete 1. Occurs within the ovary of a plant 2. Pollen tube grows down from the stigma to the ovary through the style 3. the gamete is now the seed

  8. C. Seed Dispersal: action of the seed moving from its place of origin to another site where it will grow

  9. III. Seed Structure

  10. IV. Germination Germination is the development of a new plant • Conditions needed for Germination 1. water to rehydrate dried seed tissues 2. Oxygen aerobic respiration to produce ATP. 3. Ideal temperature and pH for enzyme activity 4. Some seeds need special conditions to germinate a. fire b. testa disruption c. freezing

  11. 5. Seeds do not carry out photosynthesis • Seeds use used energy stored in cotyledons for cellular processes • This is in the form of amylose Seed Germination

  12. V. Seed Metabolism during Germination • Water is absorbed & activates cells • Synthesis of gibberelins (plant growth hormones) • Gibberelins cause synthesis of amylase • Amylase hydrolyses stored starch to maltose • Maltose is further broken down into glucose which is used for cellular respiration and converted into cellulose

  13. VI. Phytochrome & Flowering A. Photoperiodism: reaction of plants to the length of daylight (night is the critical time).

  14. B. Phytochrome: photoreceptor, a pigment in plants used to detect light. Sensitive to light in the red and far-red region -inactive form by red light (Pr) (660nm) -active form by far-red light (Pfr) (730nm) -moonlight produces a greater percentage of far-red light than sunlight, so during the night the phytochrome is slowly converted to its inactive form -more phytochrome is converted in a longer night, allowing the plant to measure the length of the night.

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