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Explain the two types of
reproduction in plants
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New material
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Asexual (or vegetative)
Maintains the same traits.
Sexual (seeds)
Very variable
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List two causes for embryo
abortion
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Non-filling
Failure to accumulate required food reserves
Empty pods
Parthenocarpy
Development of fruit without pollination
Can be natural or artificial
Example: banana
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What does it take to have a
viable seed?
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There must be both
Pollination
fertilization
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Distinguish between dioecious
and monecious
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Dioecious refers to plants with both male and
female reproductive parts.
Monecious refers to plants that have males
and females reproductive parts on separate
plants
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How are seedless water melon
made?
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Developed in Kiana Japan
1. A 2n (one from each parent) water melon treatedwith cochicine to produce a 4n plant
(during cell division the pairs do not line up because of the colchicine)
2. The 4n plant is crossed with a 2n plant to produce a3n plant
1. The 3n watermelon is seedless and allowed to flower.
3. The 3n plants (nest to en plants fields) the 2n plantsare the pollinators
Muscatine grapes works the same way.
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List the three principles of seed
propogation
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Viability of seeds
Alive, have a living embryo
Seed must be subjected to appropriateenvironmental Water
Light
Oxygen
Temperature (peppers = 90 F)
after ripening requirements = Any primarydormancy must be removed (i.e locular jelly intomato must be removed prior to germination)
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What are the three stages in
germination?
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Activation
Digestion
Seedling growth
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What happens during activation?
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Activation involves: Imbibition of water (softens the testa or seed coat)
A physical process = dead seeds also imbibe water
Enzyme activation (stored enzymes are produced-embryo) Help make more enzyme
germination
Cell elongation - first visible sign
Synthesis of enzymes Occurs within a few hrs. of imbibition
Reactivation of previously synthesized enzymes
Synthesis of new enzymes as germination starts
Cell elongation and emergence of radical First visible evidence of germination
From cell enlargement rather than from division
Emerges in few hrs or days after initiation ofgermination
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What happens during digestion
in seed germination?
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Fats, proteins, CHO stored in endosperm
digested to simpler substances
Translocation to growing points of embryo
(radicle, plumule, hypocotyl)
Active growth (synthesis of enzymes, proteins,
hormones etc)
H2O uptake and respiration continue at steady
rate
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What happens during seedling
growth of germination?
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Begins with cell division at both ends of
embryo axis
Expansion of seedling structures
Embryo consists of an axis bearing 1 or more
seed leaves (cotyledons)
Radical emerges from base of embryo axis
Plumule (growing point of shoot) from
upper end above cotyledons
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What happens to the plant once it
begins during stage II of plant
growth?
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Increase in fresh and dry weight and decrease
in weight of storage tissue
Respiratory rate increases steadily
Storage tissue ceases metabolic activity
Water uptake increases because of actively
growing seedling
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How is seed quality measured?
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Viability = germination percentage
Prompt germination
Vigorous seedling growth (hard to quantify) Should look healthy
nice green leaves
Strong stems
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What happens once seed growth
begins?
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There is increase in fresh and dry weight and a
decrease in weight of storage
RS rate increases steadily
Storage tissue ceases metabolic activity
Water uptake increases because of actively
growing seedling
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List the different types of
primary dormancy
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Seed coat dormancy
Mechanical dormancy
Chemical dormancy Morphological dormancy
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Describe what happens during
mechanical dormancy?
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Mainly in plants with seeds embedded in shell
Stone fruits peaches
They will still imbibe water but germinating
embryo will not emerge due to cementing
material that t is holding it together
Softening through microorganism
This will overcome mechanical dormancy
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What happens during chemical
dormancy?
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ABA (abscisic acid a germination inhibitors) prolong leaching withwater (example tomatoes) or remove seed covering.
Leucoanthocyanidins
prevents seed germination until the chemical inhibitors are brokendown or are no longer produced by the seed, often physiologicaldormancy is broken by a period of cool moist conditions, normallybelow (+4C) 39F, or in the case of many species in Ranunculaceaeand a few others,(-5C) 24F. Other chemicals that preventgermination are washed out of the seeds by rainwater or snowmelt. Abscisic acid is usually the growth inhibitor in seeds and itsproduction can be affected by light.
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http://en.wikipedia.org/wiki/Ranunculaceaehttp://en.wikipedia.org/wiki/Ranunculaceaehttp://en.wikipedia.org/wiki/Abscisic_acidhttp://en.wikipedia.org/wiki/Abscisic_acidhttp://en.wikipedia.org/wiki/Abscisic_acidhttp://en.wikipedia.org/wiki/Abscisic_acidhttp://en.wikipedia.org/wiki/Ranunculaceae7/30/2019 Seed Germination1
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What happen in morphological
dormancy?
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Embryo is not fully developed at time of
dissimination ( seed peels)
Enlargement occurs after the seed has
imbibed water before germination begins.
Examples:
Ginseng
Rhododendron
carrots
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Distinguish between seed dormancy
and seed coat dormancy.
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Seed dormancy
Primary dormancy
Seed is separated from
plant
Prevents immediate
germination Regulates time; conditions,
and place where germination
occurs
Seed coat dormancy
A form of primary dormancy
Testa prevents imbibitioin(water uptake)
Germination can be induced
by any method Scarification (softens seed
coat)
i.e. Chenopods = spinach,beets
Convolvalceae = sweet potatomonrning glory family
Solonaceae = tomatoes
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What is hard seededness and
how is it overcome?
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Hard seededness can happen in one of two
ways:
Naturally seed maturation during dry conditions
Artficially drying seeds at high temperatures
To overcome hard seededness:
Harvest when seeds slightly mature
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List two ways to overcome
impervious seed coats.
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1. Action of microorganism
2. Mechanical abrasion (scarification)
1. Chemical approach
1. conc H2SO4)
2. Mechanically
1. Sand paper
2. Tumbling with hard surfaces
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Distinguish between primary and
secondary dormancy
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Primary dormancy involves removal of the
after ripening requirement
Secondary dormancy is another mechanism to
prevent seed germination of an imbibed seed
if the environmental conditions are not met.
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What is secondary dormancy?
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A further adaptation to prevent germinationof imbibed seeds if the environmentalconditions are not met.
Those conditions involves: Unfavorable high temp
Unfavorable low temps
Prolonged darkness
Prolonged light (photo dormancy)
Since most seed dont need light to germinate.
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How are seeds released from
secondary dormancy?
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Induced by chilling, light, treatment with certainhormones GA
Scarification also can release 2o dormancy
Michanically Chemically (conc H2SO4)
10 min
6 hours
Wash seed to remove acid
Heat (hot water 170 to 212 F) Drop in hot water until water cools
Ei pines
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List 5 scarification methods of
overcoming domancy.
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Mechanical scarification
Sand paper, tumbler, cement mixer
Hot water 170 to 212 oF
Acid (conc H2SO4)
Warm moisture (3 4 months)
High temperature (after a forest fire)
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List 4 environmental factors
affecting germination
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Water
Temperature (extreme)
Gas exchange (O2
, CO2
)
light
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