#2 Flashcards
What is a seed?
Sexual reproduction propagule of an angionsperm
_________ are pollinated and mature to from the grass seed.
Florets
Grass seed consists of a __________sandwiched between two floral bracts, the ________- and ________.
caryopsis, lemma, palea
What is inside the caryopsis?
________
__________
_________
_____________
_____________-
Seed Coat
Pericarp
Aleurone
Embryo
Endosperm
What is the Aleurone?
Thin, proteing aceous layer, plays important role in germination
Embryo
Minature Plant
Endosperm
food supply for sustaining the plant during germination until it is capable of producting its own food through photosynthesis
What is the Scutellum?
Located between the ___________ and __________
absorbs food stored in the _________
Embryonic tissue
Coleoptile
Protective sheath of the embryonic shoot
Shoot Apex
Meristem where new shoots arise from
(From Embryo)
Coleorhiza
1.
2.
3.
- Sheath that protects the radicle
- Anchors seed in soil
- Absorbs water and nutrients from soil
3 necessry factors for germination
Water
Proper Temperature
Oxygen
What is not possible until the seed imbibes water? (Required for metabolic processes)
Germination
Break down the Biochemical Events of Germination
1.
2.
3.
4.
5
6
7
8
- Water initiates process
- Seed Absorbs water and swells and develops pressure within
- Sead coat ruptures and respiration occurs (requring O2)
- Respiration initiates biochemical and morphological events —-> plant
- Triggers scutellum to produce hormones (giberellins)
- Giberellins stimulate aleurone layer to make enzymes
- Enzymes make starch into sugar (nourishes the embryo)
- Embryo starts to grow
morphological events
1
2
3
4
5
6
7
- Caryopsis with embryo
- Seed coat cracks
- Coleorhiza emerges, anchors embryo in soil, and absorbs water - Radicle pushes through the side of coleorhiza and penetrates the soil
- primary roots emerge laterally from seed
- coleoptile emerges, heads toward surface
- roots begin to branch
- coleoptile breaks soil surface, plumule emerges through coleoptile
What happens once the Plumule emerges from the soil?
1
2
3
4
- Photosynthesis begins, seedling becomes independent of endosperm for food supply
- Now you need sunglight, food source is gone
3 Adventitious Roots develop from nodes at base of new shoot
- Seminal roots die, adventitious roots remain
Successful Seedling Development
1
2
3
4
- Available Moisture - seedling susceptible to desiccation
- Temperature- soil temps critical for germination
- Sufficient Light- Cool season grass does not require light for germination, however, some warm season grassses have a light requirement (crabgrass)
- Oxygen
