1. Processes and Requirements
Seed Germination
Processes and Requirements

2. Germination What is germination?
I have used this word before in class
It is when the first embryonic root emerges from the seed coat
Germination is a process that begins only when certain conditions are met

3. Germination
Seeds from some plants will germinate as soon as they are released
Others go dormant (a type of hibernation)
They remain dormant until proper conditions are met
What do you think some of those conditions are?

4. Types of Dormancy Stratification Scarification
Triggered by temperature
Must go through a period of cold
And then warm up
Scarification
Triggered by break-down of the seed coat
What are some ways that a hard seed coat could be broken down?

5. Stages of Germination # 1 – Imbibition
Absorption of water
Usually dormant seeds have 5-10% moisture content
At proper conditions water is imbibed very quickly
What does this do to the seed?
It swells
Becomes turgid

6. Stages of Germination # 2 – metabolic activity surges
Proteins are made
Enzymes are produced
Amylase – converts starch to sugar
Protease – breaks down stored proteins into amino acids
Sugars and amino acids are sent to meristems
That is where growth takes place
Tips of the root and shoot

7. Stages of Germination #3 – metabolic processes increase
Swelling cells break seed coat
Root tip emerges downward
Stem shoot grows upward
Shoot begins photosynthesis
Root begins absorbing water and nutrients

8. Conditions for Germination
Conditions have to be right for the new plant to survive
They include:
Water
Air
Temperatures
Light/Darkness

9. Conditions for Germination
Water triggers the process
How much moisture is usually in the seed?
Oxygen must be present for the seed to germinate
It is needed for cellular respiration
Converts stored food into energy

10. Conditions for Germination
Temperature
Some seeds can begin germinating at as low as 32°F or as high as 105°F
Optimum Temperature is usually between 65°F and 80°F
Temperature influences metabolic activity
Usually faster at higher temps and slower at lower temps

11. Conditions for Germination
To begin germination:
Some seeds actually need light
Others need darkness
Light sensitive seeds have a photoreceptor pigment in their seed coat
Called Phytochrome
It sends a message to the seed to begin or stop germination

12. Seed Quality Is seed quality important?
Why
If you buy a bag of seeds to plant, how many do you want to grow?
Good seeds make good plants

13. Seed Quality Defined by two things: Viability Vigor
Ability of seeds to germinate under optimal conditions
Vigor
Ability of seeds to germinate under different conditions and still produce healthy plants

14. Seed Quality Seed producers test seeds for germination rates
These rates are printed on the label of the seeds you buy
How do they perform the test?

15. Seed Quality
What do you do with seeds until they are sold and planted?
Store them
The goal is to maintain viability and vigor while seeds are in storage
What is the best way to store seeds?
Cool temperatures
40° is usually good
Low humidity
About 15%