Angiosperms and seed structuer and germination Flashcards
cerial daily world calorie intake
> 50%
What are the big 3
Wheat
Corn
Rice
Why are the big 3 significant
because theyre the major food crops of the world
Groups with important seeds
cereal
legumes
mustard family
embryo consists of
cotyledons
epicotle
Hypocotyl
Radicle
Plumule
Monocot where is food stored in seed
endosperm
monocot What absobs food from endosperm
cotyledon
what is the plumule enclosed and protected by
Coleoptile
another word for cotyledon
scutellum
seed coat
pericarp
Cotyledon emerges from the soil when seed germinates
epigeal germination
Cotyledon remains in soil during seed germination
hypogeal germination
Epigeal bean germination process
- Root emerges
- hypocotyl elongates to form a hook
- hook straightens and pulls cotyledons and first true leaves above ground
Hypogeal in corn process
- radicle emerges from cotyledon
- coleoptile pushed up and plumule emerges
- primary root replaced by fibrous root
seeds that survive drying or freezing.
orthdox seeds
seeds that are not able to tolerate low temp and moisture.
unorthodox seeds
are orthodox or unorthodox seeds better for being stored for prolonged periods
orthodox
Germination
beginning or resumption of growth of seed
3 main requirements for Germination
Temperature, oxygen, water
light, however less plants need light to germinate
Water germination
Most seeds go through a dessicated state before germination
unorthodox seeds cannot survive desiccation
Oxygen germination
Oxygen is used in aerobic respiration; it is present in well aerated soil in pore spaces
why does waterlogged soil usually lead to ungerminated seeds?
Hypoxic conditions
temperature germination
Seeds can germinate over a wide range of
temps
Ranges of temperature tolerance min optimum max
Minimum : 0-5°C
Maximum : around 45°C
Optimum : 20-30°C
Light germination
A few plant seeds require exposure to light to stimulate germination
most plants do not require light to germinate
What type of plants commonly need light to stimulate germination
species with very small seeds
because they store few nutrients
what pigment linked with light and germination
phytochromeW
Variable stimulated by sunlight and the colour
red, P(subscript)fr
Variable stimulated by darkness and the colour
dark red, P(subscript)r
phases of Germination
Phase 1: imbibition; weight increases exponentially
Phase 2: lag phase, shit lags
Phase 3: Radical emergence, growth again
period of growth inactivity when environmental require for germination are met and its purpose
Dormancy
Delaying mechanism, assures that seeds will germinate at the proper time.
record for seed dormancy
30000 yrs
how do most seeds break dormancy
scarification or stratification
scarification
Breaking of seed coat by mechanical action
stratification
Cold temperatures; seed needs to be chilled and kept moist
