AGR 3506 Plant Propagation - Sexual
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Advantages
• Most inexpensive• Able to multiply planting material (seeds)
most rapidly• Easy to plant• Seeds can be stored over a long period• Greater variation in plants, provide
resistance to pests & diseases• Possible to select for new genotypes
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Disadvantages
• Crops are not uniform
• Cannot guarantee quality of the crops
• Some seeds are not viable
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What are seeds ?
• the term encompasses :- fruit- Vegetative parts- True seeds
• true seeds
- Seed coat - testa
- embryo- endosperm
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Development of Seeds
• Pollination
• Fertilization
- Self pollination
- Cross pollination
- zygote → embryo- endosperm
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Seed germination
• Requirements for germination- temperature- water- oxygen- light?
• Process from seeds to seedlings
- dependent on seed viability and environment
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Seed Germination
• Seeds without endosperm• Assisted germination
- orchids
• small seeds, no endosperm
• natural germination :
with help of symbiotic mycorrhiza
• artificial germination :
in vitro - use of media under sterile conditions in laboratory
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Seed Viability
- Percentage of seeds that germinate
- Measure of viability : % germination
- Seed Testing
germination in controlled conditions rate of germination is also considered
Tetrazolium Test (2,3,5- triphenyl tetrazolium chloride)
gross measure of germination
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Seed dormancy
- Inactive phase of seeds
- causes :
- Seeds will not germinate
• impermeable seed coat
• immature embryo
• chemical factors
• unsuitable environment
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Breaking dormancy
• Scarification to make seed coats permeable – physical or chemical methods
• vernalization – low temperature
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Seed Storage
- Seeds are living organs
- seeds are stored for later use
- storage requirements depend on species
- avoid excessive respiration and enzyme activity
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Seed Storage
- method – monitor temperature, humidity, oxygen level of storage conditions. Low temperature and humidity are ideal
- low temperature storageCold room CryopreservationLiquid nitrogen : - 1960 C
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Seed Certification
- To ensure that seeds are true to type- Seed Certification- Seeds are certified by special agencies
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- 4 classification of seeds :
• Breeder Seed : breeder• Foundation Seed : from Breeder Seed• Registered Seed :
to multiply Certified Seed
• Certified Seed :