R2104 1.2 Describe the process of and requirements for seed germination

Question 1

What is seed viability?

Answer 1

Whether or not it has the capacity to grow - whether the embryo is live.

Question 2

What is a viable seed?

Answer 2

Has the potential for germination when the required external conditions are supplied

Question 3

What is seed dormancy?

Answer 3

Seeds do not germinate even when environmental conditions (water,temperature and air) are suitable

Question 4

What is germination?

Answer 4

The growth of a plant from its seed to its appearance above ground. The emergence of the young root or radicle through the testa

Question 5

Process of germination (6)

Answer 5

1. Seed starts to take in water from the micropyle
2. Increasing respiration rate
3. Breakdown of food store to release energy
4. Rapid cell division
5. Splitting of testa
6. Emergence of the radicle

Question 6

Conditions for germination

Answer 6

1. Water for chemical process to begin
2. Oxygen for respiration
3. Temperature high enough to sustain growth
4. The light level the individual seed requires

Question 7

Germination process: Water

Imbibition

Answer 7

1. Water must be increased from around 10% in a dry seed to 70% or more
2. Uptake of water is called imbibition
3. This leads to swelling and breaking of the seed coat
4. A continuous water supply is needed if germination is to proceed at a consistent rate

Question 8

Germination process: Respiration

Answer 8

1. Oxygen is essential for respiration
2. On imbibition respiration rates increase dramatically as seeds food stores are broken down to produce energy and building materials for rapid cell division
3. Soil must not be water logged or oxygen will be unavailable to the embryo
4. Oxygen is the main source of the seedlings energy until it grows leaves

Question 9

Germination process: Temperature

Answer 9

1. Different species and even seeds to the same plant germinate over a wide range of temperatures
2. Most seeds germinate slightly above room temperature - 16-24 degrees C. Others germinate just above freezing. Some seeds germinate when soil is cool -2 to -4 degrees C, and some when soil is warm 24-32 degrees C
3. Sub optimal temperatures lead to lower success rates and longer germination times

Question 10

Germination process: Light

q

Answer 10

1. Can be an environmental trigger for germination
2. Most seeds are unaffecting by light or darkness
3. However many species in forest settings will not germinate until an opening in the canpoy allow light through.

Question 11

Germination process: Overview

Answer 11

1. Imbibition of water through microphyll
2. This cause metabolic activity to resume. Hydrolytic enzymes are activated that break down the food resources into metabolically useful enzymes.
3. In the beginning respiration is anaerobic until oxygen become available
4. Respiration releases the energy stored in the seed and fuels rapid cell division
5. As it takes on water the seed swells as it rehydrates. The swelling cause the seed coat to rupture and enables the radicle to emerge
6. After the seeding emerges from the seed coat it starts growing roots and leaves. At this point food reserves are exhausted and photosynthesis should take over.

Question 12

Epigeal Germination

Phaseolus vulgaris

Answer 12

1. Phaseolus vulgaris
2. Cotyledons are brought above ground
3. Hypocotyl appear first as a bent hook , and this brings cotyledons and plumule above ground
4. The first leaves above the ground are the seed leaves. These wither as food stores are used up and then the true leaves appear.

Question 13

Hypogeal germination

Vicia faba

Answer 13

1. Broad bean germinates and the cotyledons stay below the ground.
2. Epicotyl appears above ground first, bent over in a hook, protecting the pulmule.
3. The below ground cotyledons provide food for the pulmule and radicle as they develop
4. The first leaves to appear will be the true leaves