GERMINATION:
According to ISTA it is the capability of the seed to germinate where its aspects of essential structure indicate either it is capable of germination under favourable conditions. Test is usually made on 400 pure seeds randomly selected.
Substrate
Two types of substrate are generally used
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Sand
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Paper
Growing Media & Dormancy
Growing media must have
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Good Water retention capacity
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6.0-7.5 pH
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Conductivity
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Cleanliness and freedom from toxicity
Dormancy breaking Treatments
There are certain seeds that are unable to germinate under favourable conditions so ISTA recommended additional treatments for breaking dormancy
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Pre-heating
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Pre chilling
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Soaking
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Chemical Treatment
Germination Conditions
Prepared samples shifted to germination room and germinator for different duration
Different factors affecting germination are
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Temperature
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Water
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Humidity
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Light intensity
Seedling Evaluation
Final counting takes place when seedlings attained developed structure. Evaluation of seedling takes place according to ISTA rules
Seedlings categorized into
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Normal
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Abnormal
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Dead seeds
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Hard seeds
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Fresh Un-germinated seeds
Difference of Normal & Abnormal Seedling
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Normal Seedling: Intact seedling must have well developed roots, stem and leaves
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Abnormal Seedling: Abnormal seedlings have improperly developed roots, stem and leave
Other abnormalities
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Stunted growth
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Stubby growth
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Deformed
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Necrotic
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Glassy
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Spindly
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Loops & spirals
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Split & cracks
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Decayed
Results
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Results compiled and expressed in percentage
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Round the percentage of normal seedlings up or down the nearest whole number
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Sum of all values must be equal to 100
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After compilation results forwarded to Quality Manager for further processing
VIGOR TESTING
Tetrazoilium Test
It is another method used to measure viability of seeds in shortest time period. This is a biochemical test that may be used to make a rapid assessment of seed viability.
It involves three steps
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Preconditioning (Imbibition)
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Preparation and Conditioning
Evaluation
Seeds are soaked in distill water for 24 hours then sometimes cut the seeds and then soaking the seeds in 2,3,5 triphenyl tetrazolium chloride solution for different time duration.
Final evaluation take place under high magnification of microscope using ISTA handbook on tetrazolium test.
Seed Vigor is the sum of those properties that determine the activity and performance of seed lots of acceptable germination in a wide range of environments. It provides more sensitive index of seed quality than the standard germination test.
CONDUCTIVITY TEST
Conductivity test is performed to check the leakage of electrolyte from the seeds to detect pre emergence failure due to increase of soil born fungi which interfere with its normal development
On the basis of secretion of electrolytes by seeds in the water, sowing time can be detected
Peas and beans are usually tested by this method.Two replicates of fifty seeds are placed in 500 ml beaker containing 250 ml de-ionized water.Samples are incubated at 20 °C for 24 hours. The conductivity meter readings are recorded and converted in to micromhos/cm-1.The weight and conductivity reading for the test replicates averaged and conductivity per gram of seed weight is calculated.
OTHER METHODS USED
ACCELERATED AGING TEST
COLD TEST
