Seed Germination1

7/30/2019 Seed Germination1

1/50

Explain the two types of

reproduction in plants

2/9/09

New material

1


2/50

Asexual (or vegetative)

Maintains the same traits.

Sexual (seeds)

Very variable

2


3/50

List two causes for embryo

abortion

3


4/50

Non-filling

Failure to accumulate required food reserves

Empty pods

Parthenocarpy

Development of fruit without pollination

Can be natural or artificial

Example: banana

4


5/50

What does it take to have a

viable seed?

5


6/50

There must be both

Pollination

fertilization

6


7/50

Distinguish between dioecious

and monecious

7


8/50

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

8


9/50

How are seedless water melon

made?

9


10/50

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.

10


11/50

List the three principles of seed

propogation

11


12/50

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)

12


13/50

What are the three stages in

germination?

13


14/50

Activation

Digestion

Seedling growth

14


15/50

What happens during activation?

15


16/50

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

16


17/50

What happens during digestion

in seed germination?

17


18/50

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

18


19/50

What happens during seedling

growth of germination?

19


20/50

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

20


21/50

What happens to the plant once it

begins during stage II of plant

growth?

21


22/50

2/16/09 8:51

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

22


23/50

How is seed quality measured?

23


24/50

Viability = germination percentage

Prompt germination

Vigorous seedling growth (hard to quantify) Should look healthy

nice green leaves

Strong stems

24


25/50

What happens once seed growth

begins?

25


26/50

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

26


27/50

List the different types of

primary dormancy

27


28/50

Seed coat dormancy

Mechanical dormancy

Chemical dormancy Morphological dormancy

28


29/50

Describe what happens during

mechanical dormancy?

29


30/50

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

30


31/50

What happens during chemical

dormancy?

31


32/50

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.

32
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/Ranunculaceae


33/50

What happen in morphological

dormancy?

33


34/50

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

34


35/50

Distinguish between seed dormancy

and seed coat dormancy.

35


36/50

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

36


37/50

What is hard seededness and

how is it overcome?

37


38/50

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

38


39/50

List two ways to overcome

impervious seed coats.

39


40/50

1. Action of microorganism

2. Mechanical abrasion (scarification)

1. Chemical approach

1. conc H2SO4)

2. Mechanically

1. Sand paper

2. Tumbling with hard surfaces

40


41/50

Distinguish between primary and

secondary dormancy

41


42/50

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.

42


43/50

What is secondary dormancy?

43


44/50

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.

44


45/50

How are seeds released from

secondary dormancy?

45


46/50

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

46


47/50

List 5 scarification methods of

overcoming domancy.

47


48/50

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)

48


49/50

List 4 environmental factors

affecting germination

49


50/50

Water

Temperature (extreme)

Gas exchange (O2

, CO2

)

light

Seed Germination1

Documents

Transcript of Seed Germination1