Reproduction in Flowering Plants

1. Reproduction in Flowering Plants Topic 9.3

2. Why flowers? • They smell good • They are colorful • They produce tasty nectar • They attract pollinators

3. 9.3.1 Flower Anatomy Male parts Female parts

4. 9.3.1 Draw and label a diagram showing the structure of a dicotyledonous animal pollinated flower. Know: • Sepal • Petal • Anther • Filament • Stigma • Style • Ovary

5. 9.3.2 Distinguish between pollination, fertilization, and seed dispersal. • Pollination • Transfer of pollen from anther to stigma by wind, insect etc. • Fertilization • the sperm entering the egg • Seed Dispersal • Seed = plant embryo + food reserves +testa • Seed being moved from mother plant via explosion, wind, consumption, or animal • Germination • the seed absorbing water and beginning to grow and develop

6. What is pollination? • Transfer of pollen from one anther of one flower to the stigma of another. • Can happen on the same flower: self-pollination

7. What is fertilization?Sperm entering the egg

8. 9.3 Reproduction in Angiospermophytes

9. 9.3.3 Dicot seed structure The IB calls the seed coat a “testa”

10. Seed dispersal • Seeds are dispersed in various manners: • Wind • Water • Animals • The structure of seeds indicates their dispersal type

11. 9.3.4 Germinationof Seeds • Conditions required: • Moisture • Needed so that metabolic action can take place • Temperature • Oxygen • A period of dormancy • Some conditions differ depending on seed and its environment

12. 9.3.4 Explain the conditions needed for the germination of a typical seed. Conditions vary among species • Depth of soil • Consumption by animals -- Seed is excreted in fertilizer • Water****** most important • Most species require an increase in moisture • Temperature • Some species require intense heat (fire) • Some species require a cold season followed by warmth Germination often follows Fire, drought or flood

13. 9.3.5 Outline the metabolic processes during germination of a starchy seed. • Water enters through the micropyle • Gibberellin(a plant hormone) is produced in the cotyledon • Gibberellin stimulates the production of the amylase. • Amylase catalyses the breakdown of starch into maltose • Maltose diffuses to the embryo for energy release and growth.

14. Germination of a dicot seed • Water is absorbed by the seed, kickstarting the formation of the hormone gibberellin Gibberellin forms here Water enters

15. Germination of a dicot seed • Gibberellin stimulates production of the enzyme amylase, which digests the starch in the seed into maltose Gibberellin Stimulates production of Amylase

16. 9.3.6 Explain how flowering is controlled in long and short day plants, including the role of phytochrome. The seasonal change in the length of the period of daylight or the period of darkness can control flowering. Long-day plants flower in the summer ,when nights have become short enough. Short –day plants flower in the autumn, when the nights have become long enough.

17. 9.3.6 Explain how flowering is controlled in long and short day plants, including the role of phytochrome. • Phytochrome—a plant pigment that receives red light, used to measure day length by plants. • When phytochrome receives red light after a dark period (night), it can signal that night is over. If the dark period was short enough, this causes a long day plant to flower. • When phytochrome receives a red light during a dark period (night) it can signal that night is over. This inhibits a short day plant from flowering, because the night was not long enough.

18. A flash of red light signals the end of the dark period. A flash of far-red light cancels the effect of the red flash. 2 forms of Phytochrome PR --Phytochrome that receives red light PFR --Phytochrome that receives far red light WhenPRreceives red light, it switches to PFR. When PFRreceives far red light, it switches to PR. In darkness, PFRconverts to PR –because it is the more stable form.

19. Phytochrome • Long-day plants flower in the summer, when nights have become short enough. Because the night is so short, enough PFRremains to signal the transcription of genes controlling flowering when the dawn breaks, and PFR receives the dawn’s far red light. • Long-day plants have a master gene that initiates flowering when switched on by PFR • Short-day plants flower in the autumn, when the nights have become long enough. PFR inhibits flowering, but breaks down before the long night is over. The dawn’s early light is received by the plant, and with no PFR, the plant begins the flowering process. • Short-day plants have a master flowering gene that is switched off by PFR