40 Questions
What is the purpose of stratification in seed germination?
To break seed dormancy by providing low temperature
Which of the following seeds requires a brief period of incubation at 40 to 50°C before germination?
Paddy (Oryza sativa)
What is the purpose of hot water treatment in seed germination?
To break hard seed coats in legumes
Which of the following chemicals is used to break seed dormancy in oat, barley, and tomato?
Potassium nitrate
What is the result of applying low levels of growth regulators like Gibberellins and Cytokinins to seeds?
Seed dormancy is broken
Which of the following light treatments helps in breaking the dormancy of photoblastic seeds like lettuce (Lactuca sativa)?
Red light
What is the purpose of presoaking seeds in 100 ppm GA3?
To break seed dormancy in sorghum
What is the reason for endogenous dormancy in seeds?
Presence of germination inhibitors
What is the relationship between seed size and injury?
Small seeds are less likely to be injured
Which shape of seed provides more protection?
Spherical seeds
What is the effect of provenance on seed longevity?
Provenance influences the longevity of seeds
What is the most critical factor influencing seed longevity?
Seed moisture content
What happens to seeds stored at high moisture content?
The loss of viability becomes very rapid
Why is it necessary to dry seeds before storage?
To prevent mold growth and extreme desiccation
What can lead to damage and loss of viability in seeds?
Micro flora, insects, and mites
How can the activity of micro flora be controlled?
By controlling relative humidity, temperature, and moisture content
What are the general requirements for seed germination?
Suitable substratum, adequate moisture, and favourable temperature
What is the purpose of using soil as a substratum in germination testing?
To confirm the evaluation made by other methods
What is the indicator dye used in the topographical tetrazolium test?
2, 3, 5 triphenyl tetrazolium chloride
Which method of germination testing is generally used for large sized seeds?
Sand
What is the result of incubating viable seeds in tetrazolium solution?
The seeds turn red
Who developed the method of tetrazolium test?
Lakon
What is the purpose of germination testing?
To determine seed viability
What is the requirement for the methods of germination testing?
Based on Rules and Guidelines laid down by ISTA
What is the principle behind the Topographical Tetrazolium Test?
Reduction of tetrazolium by dehydrogenase enzyme activity
What is the time frame for estimating seed viability using the Topographical Tetrazolium Test?
within 12-20 hours
What is an advantage of the Topographical Tetrazolium Test for dormant and slow germinating seeds?
The test is highly useful to assess their viability
What is a limitation of the Topographical Tetrazolium Test?
All of the above
What is the purpose of the Embryo-excision method?
To assess seed viability
What is a characteristic of viable embryos in the Embryo-excision method?
They remain firm and slightly enlarged
What is the purpose of the Ferric chloride test?
To detect mechanical damage
What is the result of mechanical damage in the Ferric chloride test?
Seeds turn black
What type of plants are excluded from the legislation?
Microorganisms
What characteristic must a plant variety possess to be eligible for protection under the act?
Must be new, distinct, uniform and stable
What is the purpose of compulsory licensing in the legislation?
In the public interest
What restriction is placed on farmers in the legislation?
They cannot sell branded seeds for commercial purposes
What is the purpose of the Seed Bill, 2004?
To regulate the seed industry
What is the purpose of accreditation of Indian Council of Agricultural Research centres and private organizations?
To conduct performance trials
What is the term coined by Mr. Hope Shand, the erstwhile Research Director of Rural Advancement Foundation International (RAFI), in 1998?
Terminator technology
What is the characteristic of terminator seeds?
They prevent germination after one generation
Study Notes
Seed Injury and Longevity
- Small seeds are less likely to be injured than large seeds
- Spherical seeds provide more protection than flat or irregularly shaped seeds
- Provenance (place of seed production) affects seed longevity, e.g., red clover seeds grown in Canada stored for four years with 80% germination, whereas seeds grown in England and New Zealand stored only for three years with 80% germination
- Seed moisture content is the most important factor influencing longevity, with high moisture content decreasing storage life and low moisture content causing damage due to desiccation
- Seeds should be dried to a safe limit for storability, suitable for the crop, before storage
Microflora, Insects, and Mites
- These organisms can lead to damage and loss of viability
- Microflora activity is controlled by relative humidity, temperature, and moisture content of seeds
- Treated seeds with fungicides can be stored for longer periods
Temperature Treatments
- Some seeds require exposure to chilling temperatures for germination, which can be achieved through stratification or artificial temperature control
- Brief incubation at 40-50°C can break dormancy in some seeds, e.g., paddy (Oryza sativa)
- Hot water treatment can break hard seed coats in legumes
Light Treatments
- Exposure to red light can break dormancy in photoblastic seeds, e.g., lettuce (Lactuca sativa)
Treatments with Growth Regulators and Other Chemicals
- Application of low levels of growth regulators like Gibberellins, Cytokinins, and Ethylene can break seed dormancy
- Potassium nitrate (0.2%) and thiourea (0.5-3%) can also be used to break seed dormancy in certain crops
General Requirements for Seed Germination
- Suitable substratum, adequate moisture, and favorable temperature and light are required for germination
- Crop-wise media or substrata, temperature, and duration of testing have been prescribed
Methods of Germination Testing
- Paper: Seeds can be tested for germination by placing them on, between, or in pleated strips of paper
- Sand: Seeds can be tested for germination by placing them on or in sand
- Soil: Germination can be tested using soil, but it is not recommended as a primary substratum due to inconsistent results
Rapid Methods of Testing Seed Viability
- Topographical Tetrazolium (TZ) test: Viable seeds turn red due to the presence of dehydrogenase enzyme activity when incubated in a tetrazolium solution
- Advantages of TZ-test: quick and easy estimation of seed viability, useful for dormant and slow-germinating seeds, and seeds can be used for germination after the test
- Disadvantages of TZ-test: difficulty in distinguishing between normal and abnormal seeds, and inability to detect microorganisms affecting germination
Embryo-Excision Method
- Embryos are excised from soaked seeds and incubated under normal conditions to assess viability
- Germinating embryos are considered viable
Ferric Chloride Test
- Mechanical injured areas of legume seeds turn black when placed in a ferric chloride solution, allowing for rapid assessment of mechanical damage
Factors affecting seed longevity and storability, including seed size, shape, and provenance. Understand how these factors influence seed germination.
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