1.3

Question 1

Scarification

Meaning in nature

Answer 1

In nature a hard seed coat gradually becomes permeable to water by:
passing through bird/animal digestive tract
Action of soil micro-organisms
Repeated wetting/drying
Repeated freezing /thawing

Question 2

Scarifying

Meaning

Answer 2

Scratching testa to let water and oxygen in

Or

To removes mechanical restraint eg sand papering or filing the seed coat

Question 3

Example of scarifying

Answer 3

Used on older cultivars of Lathyrus odoratus.
Seed coat is ‘chipped’ or ‘nicked’ with knife or blade, or rubbing with file
Care must be taken to avoid damaging the embryo.
Best site - immediately above the tips of cotyledons.
Temp 13-18 degrees C
Approx 30 days

Question 4

After ripening

Definition

Answer 4

• Storing in warm conditions
• without moisture
  Allows embryos to mature if necessary.

Question 5

Examples of after ripening to overcome seed dormancy.

Answer 5

Ilex aquifolium
Fraxinus excelsior
Solanum lycopersicum
Carrots
Parsnips
Tropical palms

Question 6

Example of moist stratification

Answer 6

Fraxinus excelsior

Moist, warm stratification in sand, peat or vermiculite.

60 days at 20 C
12 - 16 weeks cold stratification at 1 - 5 C

Question 7

Soaking

Answer 7

Eg. Cerci siliquastrum

Pour boiling water over seeds to promote germination
Germination occurs between 30 and 90 days at 13-16 C

Question 8

Chemical treatments

Answer 8

Usually used commercially.

Sulphuric acid is used for Gleditsia triacthus

Question 9

Cold stratification

Answer 9

Seeds are mixed with moist sand, peat or peat substitute in polythene bag. 4 parts substrate to 1 part seeds.
Seeds allowed to take up water in warm.
Once swollen bag is chilled about 1 - 5 C
Bag should be shaking occasionally to aerate contents.
Some species germinate as soon as chilling period is completed, others need normal germination requirements.

Question 10

Warm stratification

Answer 10

Temp 15 - 20 C
Moist conditions
Up to 12 weeks
Then cold stratification ‘winter’ treatment
Reduces germination inhibitors or increases promoters.
Thought to influence seed coat permeability and embryo development.

Question 11

Fire and smoke

Answer 11

Some seeds do not germinate naturally until fire has cleared an area of vegetation. The heat of the fire causes the seed coat to fracture after ripening of embryo.

Chemicals in smoke can also break dormancy.

Common in South African plants eg.Protea spp.

Question 12

Plant growth regulators

Answer 12

Zea mays

Responds to application of mix of gibberellins to break dormancy.