Seed Germination and Dormancy (Lab, Exercises 2 and 3) Flashcards
(22 cards)
A protective sheath that covers the emerging shoot (plumule) as it grows upward through the soil. Only found in monocots
Coleoptile
The part of the embryo between the cotyledons (seed leaves) and the radicle (embryonic root). Only found in dicots
Hypocotyl
Refers to the ability of a seed to germinate and form a mature individual
Viability
Seed type that has germination stimulated by
the presence of light
Positive Photoblastic
Light-inhibited seed type
Negative Photoblastic
Seed type that is light-insensitive, it germinates either in light or dark conditions
Neutral Photoblastic
A measure that combines germination speed and germination percentage into a single value, giving a better picture of both how fast and how many seeds germinate
Timson’s Germination Index
Indicates a faster and more complete germination (using TGI)
Higher TGI Value
TGI Equation
% IGV = ∑ G/t
Whereas:
G = percentage of seeds germinated at 2 day intervals
t = total germination period
Expected photoblastic types of Exercise 2 plants (Theoretical, my best guess)***
- Cucumis melo: Neutral Photoblastic
- Vigna unguiculata: Neutral photoblastic
- Solanum lycopersicum: Negatively Photoblastic
- Thymus vulgaris: Neutral Photoblastic
- Allium cepa: Negatively Photoblastic
- Cucumis sativus: Positively Photoblastic
Photoreceptors with roles in seed germination and seedling growth
Phytochrome (Red and Far-red light) and Cryptochrome (Blue and UV light)
Biologically active form of phytochrome
Pfr
Effects on hormones GA and ABA by Pfr
Suppresses ABA promotes GA
Basic requirements for seed germination
- Adequate water
- Oxygen
- Optimum temperature
- Light
- Nitrate
Most abundant
form of seed dormancy. It prevents seed germination until chemical changes
occur. Characterized by the presence of chemical inhibitors
Physiological Dormancy
Seed dormancy where seeds have underdeveloped
embryos, but is
differentiated. The embryos need time to grow and
germinate
Morphological Dormancy
Seed dormancy where seeds have water impermeable layers of palisade cells in the coat
Physical Dormancy
Methods used to break or weaken the seed coat to break seed dormancy
Scarification
Methods that simulate natural cold/dormancy-breaking conditions to break seed dormancy
Stratification
Expected photoblastic types of Exercise 3 plants (Theoretical, my best guess)***
- Cassia fistula: Scarification
- Leucaena leucocephala: Scarification
- Luffa acutangula: Stratification
Source of imposed dormancy due to the physical barrier of the seed coat or its chemical inhibitors. Broken by scarification
Coat-Imposed Dormancy
Source of imposed dormancy due to and underdeveloped embryo that is not ready to grow even if water and oxygen are available. Controlled by internal factors such as hormones. Broken by stratification
Embryo-Imposed Dormancy
