R2104 1.1 Describe the structure of seeds and their significance in propagation

Question 1

What is a seed?

Answer 1

• A seed is a product of sexual reproduction
• Seeds are structures that develop from the fertilised ovule in seed bearing plants
• Haploid cells from one parent plant combine with haploid cells from another plant. This recombination to form a diploid seed is sexual reproduction

Question 2

Benefits of sexual reproduction

Answer 2

1. Variety - helps plants survive and spread
2. Greater variation in genetic material enables plants to adapt to changin conditions
3. Inherited weakness cannot become dominant
4. Seeds survive in the ground for a long time. Germination can be staggered over long time intervals, which increase chances of survival
5. Fruits have many different mechanisms to spread seeds over large distances and colonise new areas

Question 3

Horticultural benefits of propagation from seed (5)

Answer 3

1. It produces variation from which new cultivars can be developed. Main method of producing new cultivars.
2. Seed can generally be stored easily and remain viable for a long period
3. Cheapest and easiest method of producing large numbers of plants
4. It may be the only way of propagating some species
5. It can be a way to avoid virus transmission
6. Provenance can be carefully sourced
7. Guaranteed seed sources are available

Question 4

Horticultural limitations of propagation from seed (6)

Answer 4

1. Some plants produce no viable seed
2. Certain seeds do not store easily
3. Lack of uniformity. Seed raised plants are variable in colour, form and vigour - for example a lack of consistency in bedding plants
4. Seed-raised plants can take longer to reach maturity (apple and pear trees)
5. Unique characteristics such as disease resistance will not necessarily be maintained when plant is propagated from seed
6. Some seeds are slow or difficult to germinate. sometimes with dormancy mechanisms to overcome

Question 5

3 major parts of a seed

Answer 5

1. An embryo
2. A food store to fuel growth
3. A protective outer coat to keep embryo safe and make sure it does not dry out before conditions are right for germination

Question 6

Parts of a seed: Testa

Answer 6

1. Protective seed coat
2. Can be tough and may need to be damaged before it can germinate
3. Formed from outer layers surrounding ovule

Question 7

Parts of a seed: Embryo

Answer 7

1. Young plant contained in the seed
2. Consists of: cotyledon(s), plumule, hypocotyl, epicotyl and radicle

Question 8

Parts of a seed: Cotyledon

Answer 8

Seed leaf that provides a store of food for the germinating seed. May be one or two cotyledons

Question 9

Parts of a seed: Plumule

Answer 9

Part of the seed that becomes the first shoot

Question 10

Parts of a seed: Radicle

Answer 10

Part of the seed that becomes the first root

Question 11

Parts of a seed: Hilum

Answer 11

Point where seed was attached within ovary

Question 12

Parts of a seed: Micropyle

Answer 12

Where the pollen tube entered the ovule during fertilisation.
Sometimes water can enter here and trigger germination

Question 13

Parts of a seed: Hypocotyl

Answer 13

Connects pulmule to radicle. Lies below cotyledons and gives rise to the root

Question 14

Parts of a seed: Epicotyl

Answer 14

Between pulmule and radicle. Is above the cotyledons and gives rise to the stem

Question 15

Examples of plants usually propagated from seed (6)

Answer 15

1. Daucus carota
2. Phaseolus vulgaris
3. Solanum lycopersicum
4. Lobelia erinus
5. Nigella damascena
6. Lolium perenne

Question 16

Main horticultural use of seed propagation with
Examples of plant types and their seed

Answer 16

1. Vegetable growing e.g Daucus carota, Phaseolus vulgaris
2. Bedding plant production e.g. Lobelia erinus
3. Annual / biennial flowers e.g Nigella damascena, Cosmos bipinnatus
4. Fruits e.g. Solanum lycopersicum
5. Lawn grasses e.g Lolium perenne
6. Native trees and shrubs e.g. Quercus robur, Crataegus monogyna
7. Perennial plants e.g. Dainthus deltoides