Seeds and Seed Dispersal Flashcards
What is the role of seeds?
To protect and nourish embryos allowing embryos to survive a wide range of environmental conditions
Allow species to survive and regenerate
What is a dormant state?
Enables plant species to disperse into new environments and wait for good conditions to germinate
What does it mean to be viable?
They can germinate
What is the record for seeds persisting at non-freezing temperatures?
2,000 years
How do gymnosperm seeds develop?
From ovules
Lack a surrounding fruit
What is a seed wing?
An extension of a seed coat which aid in seed dispersal.
What does it mean to not be a fruit?
Not derived from an ovary
What is the outermost layer of the seed?
The seed coat
Where does the seed coat originate?
From the mother tree (sporophyte) so it is diploid
What does resin do?
Plays a role in seed dormancy, protecting the embryo from losing water, and deterring seed herbivore.
What is a megagametophyte?
The female gametophyte
Haploid from meiosis
produces eggs
Produces nutritional tissue to protect the embryo
What does fertilization do?
Produces embryos of new sporophytes which are diploid
What does an embryo consist of?
Cotyledons
Hypocotyl
Radicle
What is cotyledons?
embryonic leaves (the number of cotyledons is species dependent)
What is the hypocotyl
embryonic stem
What is a radical?
embryonic root
What is the shoot apical meristem?
a region of cells that has the ability to divide and create all the cells and tissues needed for new stem and leaves
What is the root apical meristem?
a region of cells that has the ability to divide and create all the cells and tissues needed for new roots
What is a root cap?
a covering that allows the root to grow through soil undamaged
Why are embryos oriented in some seeds?
So cotyledons and shoot apical meristems point towards the wider end of the seed so the radicle is near the narrower end of the seed
How do you know if a conifer is mature?
- If the embryo fills most of the cavity
2. The megagametophyte appears firm and waxy
What do cone scales do?
Flex and release seeds
What conditions promote flexing of cone scales?
Dry conditions
Why do conifers have seed cones that hang downwards
Takes advantage of gravity and wind to assist in seed dispersal
What does a seedbed do?
Promotes successful germination and early growth
Where are angiosperm seeds found?
Inside the fruit
What are some common features between gymnosperm seeds and angiosperm seeds?
Surrounded by a seed coat Have cotyledons (embryonic leaves) Shoot and root apical meristems Hypocotyl (embryonic shoot) Radicle (embryonic root)
What is the endosperm?
A tissue that holds nutritive reserves for the angiosperm embryo.
How is the endosperm produced?
Through the fertilization process in flowering plants
An embryo produces endosperm that is triploid and the endosperm will nourish and protect the developing embryo
What are cotyledons like in angiosperm seeds?
They are a lot larger
There can be one or two
What are monocot seeds like?
Have endosperm at maturity
Single cotyledon to absorb food
How are seeds dispersed?
Via animals
Wind dispersed
What is the magagemetophyte and what does it do?
The female gametophyte
Produces eggs when young
Becomes nutritional tissue in mature tree
Embryo is embedded in it
What does the suspensor do?
Pushes embryo into megagemtophyte
When are Douglas Fir seeds ready?
August and September
Cones are full size in july but mature later
What is the sctellum?
Cotyledon modified for food absorption
What is the coleoptile?
Protects and guides the plumule
What is the coleorhiza
Protects the radical
