1. PLANT REPRODUCTION CONCEPTS- Seed Production
UNIT THREE
PLANT REPRODUCTION CONCEPTS- Seed Production

2. So far in Unit 3 we have talked about plant cell structure and Mendelian genetics. In this lecture we will
take a break from Mendel and look at the plant seed. The
seed will carry genetic information from one generation to the
Next…..so it is worthy of this brief detour

3. Plant Reproduction Concepts
Seed Dormancy
Seed Germination

4. Seed Dormancy
“The resting state or quiescence period that occurs in many plant species…but causes are not always the same”
May be a survival mechanism
Woody perennials in autumn (apples)
Allows embryonic plant to overwinter in seed form or some form of cold reistance

5. Seed Dormancy Seed Coat Dormancy (Go to next slide)
Seed coats surrounding embryo may be impermeable to water and gasses
Common in hard seed coat types like alfalfa, clovers, as well as some tree species
Seed coats may be softened by:
Scarification, mechanical abrasion
Heat treatment
brief exposure to boiling water
Acid scarification

6. The Seed Coat in a dicotyledon
Embryo
The Seed Coat in a dicotyledon

7. Seed Dormancy Seed Coat Dormancy
Seed coats surrounding embryo may be impermeable to water and gasses
Common in hard seed coat types like alfalfa, clovers, as well as some tree species
Seed coats may be softened by:
Scarification, mechanical abrasion
Heat treatment
brief exposure to boiling water
Acid scarification

8. Seed Dormancy Embryo dormancy Double dormancy
Common in woody perennials (black walnut)
Results from physiological or metabolic blocks that need to be removed
Stratification
exposed to chilling conditions and moist soils, will germinate in spring
Double dormancy
Seed coat and embryo dormancy in same species

9. Seed Dormancy Rudimentary embryos Chemical inhibitors
Fruits (seeds) discarded or shed before they are mature
Needs weeks or months to mature and germinate
Chemical inhibitors
Inhibitors may be found in endosperm that prevent or delay germination
Often leaching of seeds or exposure to rain will remove chemical inhibitors

10. Seed Germination Sequence of events in seed germination:
Imbibition of water  activation of hormones, enzymes  embryo growth  root and shoot differentiation(seedling establishment)

12. Bean plant on left showing epigeal germination; corn plant on right showing hypogeal germination ( Do you know the difference?)

13. Germination Requirements
Adequate moisture
Proper temperature
Good aeration
Light (in some species)
Freedom from pathogenic organisms
Freedom from toxic salts

14. “The End of a Perfect Day in Plant Science”
by Kinkade