Seed dormancy and Germination Flashcards
What is dormancy?
The physiological control of the embryo
What does embryo dormancy do?
Levels the plant growth regulators (hormones)
Have growth-inhibitors and lack growth promoters
How is dormancy overcome?
Through exposure to low temperatures which meet chilling requirements of the seed
Artificially applying growth regulators
What is embryo immaturity?
Some species are immature at the time fruit shed
What is seed coat impermeability?
Impermeable to water or oxygen which imposes dormancy through preventing growth
Seeds need scarification
What is seed coat dormancy?
Have chemical growth inhibtors in the seed coat that need to be leached out by water before seeds will germinate
What is the light requirement?
Some species require exposure to dim light in order to germinate
What type of light promotes germination?
Red light
But far red light inhibtis it
What is phytochrome?
The pigment that percieves light
What is serotiny
Cone scales are glued by resin and must be exposed to warm temperatures to open
so serotinous cones are encouraged to open
needs heat
Can some seeds lack domancy?
Yes, lodgepone pine and red alder lack dromancy
What is germination?
the resumption of growth by embryos when exposed to favorable conditions
What steps are needed for germination?
- Seeds swell so the seed coat ruptures
- Cell division occurs in the embryo and radicle elongates and extends out of the seed
- Hormones produces initiate enzymatic activity
- Elongation of the hypocotyl pushes cotyledons aboveground and the epicotyl grows
When is the process of germination complete?
when enough photosynthetic tissue is exposed to support further growth.
What does it mean to be positively gravitrophic?
Grows in the direction of the gravitational pull
