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Germination

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Learning objectives (3/4) Define the term: Germination. Explain the factors necessary for and role of digestion and respiration in germination. Outline the stages of seed development 2

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1.What are the 3 factors needed for germination 2.What is germination 3.3.

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Germination Growth of seed or embryo into a plant 4

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Germination Factors necessary Water Oxygen Suitable temperature or Warmth Mnemonic: WOW Dormancy must be complete 5

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Germination Factors necessary Water Activates enzymes which break down food reserves in endosperm/cotyledon Medium for germination reactions e.g. digestion Transport medium for digested products 6

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Germination Factors necessary Oxygen Needed for cellular respiration Suitable temperature Allows maximum enzyme activity 7

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Events in Germination (detail) http://www.youtube.com/watch?v=TJQyL-7KRmw http://www.youtube.com/watch?v=TJQyL-7KRmw 1.Water is absorbed 1.Food reserves are digested in the endosperm and cotyledon to allow the food to change 2.Digested food is moved to the embryo for respiration 2.New cells are produced using amino acids 3.Glucose is turned into ATP to drive cell division 4.Radicle breaks through the testa 5.Plumule emerges above ground 6.New leaves begin to photosynthesise 8 Events in germination cease when the plants leaves have developed and the plant has started to photosynthesise

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Events in Germination Plumule Radicle Cotyledon 9

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Events in Germination Plumule Radicle 10

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Mass drops initially due to respiration, but then begins to increase due to photosynthesis Changes in dry weight of seeds during germination 11

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Food reserves in endosperm are transferred to the growing embryo Changes in dry weight of seeds during germination 12

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Germination of broad bean (hypogeal) 13

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Germination of broad bean (hypogeal) 14

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Seed water is absorbed through the micropyle Ground Germination of broad bean 15

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The testa splits Radicle emerges Germination of broad bean 16

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Radicle continues to grow Plumule emerges Germination of broad bean 17

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The plumule is hooked to protect the leaves at the tip Epicotyl Germination of broad bean 18

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The plumule grows above the surface of the soil Lateral roots develop Germination of broad bean 19

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Plumule straightens and the leaves open out Throughout Hypogeal germination the cotyledons remain below the ground Germination of broad bean 20

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Seed water is absorbed through the micropyle Germination of sunflower (Epigael) 21

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Radicle emerges Germination of sunflower 22

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Hypocotyl Hook Germination of sunflower 23

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Radicle grows downwards Seed coat discarded Cotyledons Germination of sunflower 24

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Leaves emerge Cotyledons wither Germination of sunflower In Epigeal germination the cotyledons rise above the ground 25

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Review the plant life cycle 1 4 2 pollen is transferred 3 After fertilization flower withers seeds disperse and germinate into new plant seeds develop in ovary 4 26

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Learning Check 1.Define germination 2.List the conditions of germination 3.Briefly describe the events in germination 4.When does germination stop 5.What is the difference in hypogeal and epigeal germination 27

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Can you Define the term: Germination. Explain the factors necessary for and role of digestion and respiration in germination. Outline the stages of seed development 28