Seed Structure and Germination Flashcards
What genus’ contain important seeds
- Poaceae: cereals
- Fabaceae: legumes
- Brassicaceae: mustard
What are the big 3 major food crops worldwide?
Wheat, corn, and rice
Explain the seed structure of corn (monocot)
- Food source and starch is stored in endosperm
- Cotyledon absorbs
- Plumule is enclosed by the coleoptile
- Radicle is enclosed by the coleorhiza
- Pericarp is the seed coat
Epigeal vs hypogeal germination
Epigeal: the cotyledons emerge above the soil
Hypogeal: cotyledons stay in the soil
Explain the steps of a epigeous germination
- root emerges
- hypocotyl emerges and forms a hook
- hook straightens and pull cotyledons and true leaves above ground
Explain the steps of hypogeous germination
- radicle emerges from coleorhiza
- coleoptile pushes up, causing the plumule to emerge
Define orthodox seeds
Seeds that survive drying and freezing - easy to preserve
Define unorthodox seeds (recalcitrant)
Seeds lose their viability when exposed to low temperature and moisture
4 requirements for germination:
Water, oxygen, temperature, light
Germination: explain water
Germination: explain oxygen
- oxygen uses aerobic respiration in soil pore spaces
- can undergo hypoxic conditions where there is not enough oxygen to maintain homeostasis and the plants don’t germinate
Germination: explain temperature
Seeds germinate at a range of temperatures:
- min: 0-5C
- max: around 45C
-optimum: 20-30C
Germination: explain light
MOST plants don’t require light to germinate, but they use phytochrome pigment (Pr and Pfr)
What are the 3 phases of germination?
- inhibition
- lag phase
- radicle emergence
Explain dormancy
Definition: period of growth inactivity
Function: delays mechanism and assures that the seeds germinate at the right time
