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Seed Dormancy and Population Models in Plant Species

Explore the concept of seed dormancy and its importance in population dynamics in plants. Learn about different dormancy mechanisms and population models used to study plant populations.

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Seed Dormancy and Population Models in Plant Species

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  1. Ch. 5: Population Structure and Changes

  2. Plants “Special” • High phenotypic plasticity (Done) • Indeterminant growth (Done) • Clonal growth (Done) • Seed dormancy Dana Carvey as the Church Lady

  3. Plant Features • 4) Seed dormancy • Dormancy: arrested growth embryo • Lupinus arcticus (10,000 yr) • (arctic lupine) • Lotus (400 yr)

  4. Seed dormancy • Seed bank: pop’n dormant seeds • In soil

  5. Seed dormancy • Seed bank (/m2): • Ag fields: 20,000-40,000 • Tropical forest: <1,000 • Subarctic forest: 10-100

  6. Seed dormancy • Seed bank: population dormant seeds • On plant • closed cone pines (ex, knobcone pine) • Serotinous cones (open postfire) • Banksia (Australia)

  7. Dormancy mechanisms • 1) incomplete embryo development

  8. Dormancy mechanisms • 2) biochemical trigger • environment cue starts germ. • stratification: cold) • sumorization: heat. Some desert annuals. Max. germ.: 50 C, 4 wk

  9. Dormancy mechanisms • 3) impermeable seed coat/fruit wall • scarification: breaks Sand paper!

  10. Dormancy mechanisms • Scarification: Fire • Ex: chaparral (shrub vegetation: Mediterranean climate) • Pine Hill flannel bush (Fremontodendron decumbens) • Best germ.: 5 min @ 100 C! Another study by Tony Danza!

  11. Dormancy mechanisms • Scarification: Mechanical abrasion • Ex, smoke tree in arroyo (

  12. Dormancy mechanisms • 4) germination inhibitors (seed coat/fruit wall)

  13. Importance of seed banks • 1) May differ from vegetation • Ex, African rain forest • 147 tree spp. • 22 in seed bank (none same as growing)

  14. Importance of seed banks • 2) Most pop’n: seed bank • Ex, CA annual grassland. • 100 grasses/m2, 30,000 seeds/m2

  15. Importance of seed banks • 3) Seed bank genetic reservoir • Differ from

  16. Ch. 5: Population Structure and Changes

  17. Population Models • 1) Simple discrete-time model • N(t) = number now • Future time (t+1): • N(t+1)=N(t) + B + I - D – E

  18. Population Models • 1) Simple discrete-time model • Usu. ignore I & E

  19. Population Models • 1) Simple discrete-time model • Usu. ignore I & E • Important metapopulations ( • Ex, Cakile (sea rocket)

  20. Population Models • Ex, Cakile (sea rocket) summer winter Tony D!

  21. Population Models • Ex, Cakile (sea rocket) • Beach pop’n “source”, dune “sink” pop’n winter summer

  22. Population Models • 1) Simple discrete-time model • Nt = number now • At time (t+1): • N(t+1)=Nt + B + I - D – E

  23. Population Models • 2) Continuous time models • b=birth rate • d=death rate • rmax=b-d; intrinsic rate of natural increase • Rate pop’n change=dN/dt • dN/dt=Nrmax Curve?

  24. Population Models • 2) Continuous time models • dN/dt=Nrmax • Exponential growth. Ideal conditions…

  25. Population Models • 2) Continuous time models • Limiting • Logistic growth. Pop. max. @ K (carrying capacity):

  26. Population Models • 2) Continuous time models • Eqn.? Start dN/dt=Nrmax • Add “scaling factor” (K-N)/K • dN/dt=Nrmax (K-N)/K • N small, (K-N)/K almost 1 • N near K, (K-N)/K very small

  27. Population Models • Plant Point 1: K based on density • Animals: most inds. • Plants: hi modular • Crowding capacity: combine density

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