BIOL 111 Lecture Notes - Gametophyte, Epicotyl, Gamete

7 views3 pages
22/09/11
All organisms show growth and development:
Growth: Quantitative irreversible increase in any cell parameters (eg. height,
volume, weight, number in populations, etc…)
Development: Qualitative changes in body structure or function at certain stages of
life cycle (eg. Development of organs [organogensis], achieving final shape
[morphogenesis] and size juvenile/adult phase, etc)
- Growth and development (size and shape) regulated by hormones
1) absicic acid: stress hormone
2) auxins: promotes stem elogation
3) brassinosteroids: related to steroid hormones in mammals
4) cytokinins: cell devision
5) ethylene: fruit ripening
6) gibberellins: seed germination
Growth graph: (number of cell per mL) vs Time S shape graph
- Small population, logarithmic growth, stationary phase (stable
population)
Effect of auxins on plant growth:
Tropic Growth Movements: shoot tips show positive phototropic growth
- coleoptile (conical structure which emerges from the soil) contains first
leaf:
o Auxin hormone stimulates shaded cells to grow more than cells in
the light, causing plant to bend towards the light
o Light perceived by apical tip of the coleoptile, bend occurs below
- Cell on its side: gravity pulls auxins to the bottom side = more growth,
growth of cells at bottom force plant to bend upwards
- Toxic to roots inhibits root growth, root will grow opposite way than
stem will grow, cells exposed to auxin will grow less so root will bend
towards cells with auxin
- Promotes apical dominance: diverts resources to upward growth of
plants, if apical part is cut lateral braches will grow.
Seed Germination:
Development of seed will depend on:
- Size of the seed: Small seeds germinate in response to light, if they are too
deep they cannot reach the surface before exhausting resources found in
cotyledon
- Seeds dormancy: Absicisc acid (ABA) allows for seed dormancy. When ABA
leeches out
- Gibberellins present: = germination
- Strength of seed coat: strong coat = difficult for roots to penetrate the seed
coat
Light requirement for seed germination:
Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.