4.Seed Germination, Harvesting and Storing Flashcards
What is a seed?
A seed is the product of sexual reproduction. Formed from ovules as a result of fertilisation. Method by which plants reproduce.
What is a Testa?
- Seed coat for protection
- Tough outer shell
- May need damaging before germination - nicking, soaking, soil particles etc.
Horticultural benefits of propagation from seed
- Produces variation/adapt, evolve, survive
- Only method for some species
- Can get large numbers from one plant
- Easily stored - sometimes for many years
- Cheap
- Can prevent virus transmission
- E.g Nigella damascena
What are the limitations for propagation by seed?
- Some plants may not produce viable seed
- Lack of uniformity
- Difficult germination - may have deep dormancy and need scarification
- Some seeds don’t store easily (recalcitrant - need warm humid conditions)
- Time to maturity - seed may not be produced for many years
- Cultivar names can only be used when the new plant is identical to the parent
What is a viable seed?
- Has the potential for germination when conditions are right. Contains living embryo
- Can vary between species from a few weeks to centuries
What is seed dormancy?
- When viable seed fails to germinate even when all germination conditions have been met
- Prevented by germination by a chemical ‘lock’
- Can only be ended by a particular conditions
- E.g cold then warm temp/ digestive juices after being eaten
- Scarification / stratification can often be used to help encourage germination
Describe changes in germinating seed
- Takes in water - often through soft/damaged area of testa
- Respiration rate increases
- Breakdown of food store
- Rapid cell division
- Splitting of seed coat/testa
- Emergence of radicle
Describe general preparation and storage of seeds.
- Collect ripe seed (when seed pods are brown)
- Choose ones that are pest and disease free and true to type
- Store pods and capsules in a warm place until they split
- Clean the seed so is free from dust and debris (sieve)
- Place in paper bag to be kept dry and cool
- Lidded plastic box with silica gel in fridge
- Label and date
- Protect from rodents
- Once packet is open the ageing process will begin
When should seed be harvested?
- As seed ripens (in most cases)
- Seed from dry fruits should be collected on a dry day
- Dry on the plant for as long as possible into the autumn, ideally until the pods become so dry they are crispy
- If this is not possible, uproot the plants and hang them upside down somewhere warm until the pods are completely dry
What are recalcitrant seeds?
Give example.
- Moist/fleshy seed that easily lose their viability if stored for any length of time
- They cannot have moisture content below 20–30% w/o injury.
- Includes many tropical plants
- Difficult to store and conservation is problematic.
- Mangifera indica (Mango)
- Quercus robur (English Oak)
What are orthodox seeds?
Give examples of vegetables and flowers.
- Dry seed, must be kept in cool/dry conditions when stored
1. Daucus carota (carrot)
2. Nigella damascena
What is seed viability/germination affected by?
- The condition of the seed when first stored
- How long it is stored (viability diminishes over time)
- What seed is being kept
- Whether respiration is controlled (the aim is to slow down respiration. If respiration is not controlled then seeds may use up food needed to produce strong, healthy plants.
- Dormancy – some seeds may become dormant if stored and to promote germination dormancy must be broken
Describe preparation and storage of Solanum lycopericum (Tomato) fruits for seed storage.
• Harvesting
Harvest healthy fruit which is free from damage when it is ripe/fully mature.
• Maceration
Macerate the fruit by pressing the fruit with a board, squashing by hand or scooping out the seeds from the flesh
• Separation
The seeds can be separated from the flesh by placing the pulp in a bucket of water for a few days. The flesh and dead seeds float and the live seeds sink to the bottom. Seeds can be separated with the use of a sieve.
• Drying
Dry in airy place or in gentle heat; on greaseproof paper
- Store
Place in a labelled paper bag and in a seed tin or plastic container with silica gel
