II. GERMINATION TEST:
Germination testing is considered as the most important quality test in evaluating the planting value of a seed lot. The ability of seeds to produce normal seedlings and plants later on is measured in terms of germination test. Testing of seeds under field conditions is normally unsatisfactory as the results cannot be reproduced with reliability. Laboratory methods then have been conceived wherein the external factors are controlled to give the most uniform, rapid and complete germination. Testing conditions in the laboratory have been standardized to enable the test results to be reproduced within limits as nearly as possible as those determined by random sample variation.
Objective
The ultimate objective of seed germination testing is to obtain information with respect to the planting value of the seed and to provide results which could be used to compare the value of different seed lots.
Definition
Germination of a seed lot in a laboratory is the emergence and development of the seedling to a stage where the aspect of its essential structures indicates whether or not it is able to develop further into a satisfactory plant under favourable conditions in soil (ISTA, 1985). These essential structures are a well-developed and intact root system, hypocotyl, plumule and one or two cotyledons according to the species Seedlings cannot be evaluated in a germination test until these essential structures are clearly identifiable and the reported percentage germination expresses the proportion of seeds which have produced normal seedlings within the period specified for each species.
General Principles
Germination tests shall be made with seeds from the pure seed fraction of a purity test. A minimum of four hundred seeds are required in four replicates of 100 seeds each or eight replicates of 50 seeds each or 16 replications of 25 seeds each depending on the size of seeds and size of containers of substrate.
The seeds shall receive no pretreatments excepting those recommended in the following Table.
TABLE-1
|
Crop |
Media |
Temperature |
1st count |
Final count |
Addl.directions |
|
Paddy |
BP, TP,S |
20-30,25 |
5 |
14 |
Preheat(50° C) Soak in water or HNO3 24 hours |
|
Ragi |
TP, BP |
20-30 |
4 |
8 |
0.2% KNO3(2 to 3 hours) |
|
Maize |
BP, S |
20-30, 25 |
4 |
7 |
- |
|
Cumbu |
TP, BP |
20-30 |
3 |
7 |
0.2% KNO3(2 to 3 hours) |
|
Sorghum |
TP, BP |
20-30, 25 |
4 |
10 |
Prechill |
|
Bengal gram |
BP, S |
20-30, 20 |
5 |
8 |
- |
|
Blackgram |
BP, S |
20-30, 25 |
4 |
7 |
- |
|
Cowpea |
BP, S |
20-30, 20 |
5 |
8 |
- |
|
French bean |
BP, S |
20-30, 25,20 |
5 |
9 |
- |
|
Greengram |
BP, S |
20-30, 25 |
5 |
8 |
- |
|
Horsegram |
BP |
30 |
3 |
5 |
- |
|
Peas |
BP,s |
20 |
5 |
8 |
- |
|
Redgram |
BP, S |
30 |
4 |
6 |
- |
|
Castor |
BP, S |
20-30 |
7 |
14 |
- |
|
Groundnut |
BP, S |
20-30, 25 |
5 |
10 |
Remove shells, Pre heat 40° C |
|
Gingelly |
TP |
20-30 |
3 |
6 |
- |
|
Soya bean |
BP, S |
20-30,25 |
5 |
8 |
- |
|
Sunflower |
BP, S |
20-30, 25 |
4 |
10 |
Ethrel 25ppm 48 hrs |
|
Cotton |
BP, S |
20-30, 25 |
4 |
12 |
Hotwater(85°C-1 minute) |
|
Sun hemp |
BP, S |
20-30 |
4 |
10 |
- |
|
Cluster bean |
BP |
20-30 |
5 |
14 |
- |
|
Oat |
BP, S |
20 |
5 |
10 |
Preheat30-35°c prechill |
|
Dhaincha |
TP,BP |
20-30 |
5 |
7 |
Rub seed coat on paper |
|
Sugar beet |
TP,BP,S |
20-30;15-25 |
4 |
14 |
Prewash multigerm 2hrs,monogerm 4hrs |
|
Ashgourd |
S |
30-35 |
5 |
14 |
Light |
|
Bittergourd |
BP,S |
20-30,30 |
4 |
14 |
- |
|
Bottlegourd |
BP,S |
20-30 |
4 |
14 |
- |
|
Cucumber |
TP,BP,S |
20-30,25 |
4 |
8 |
- |
|
Pumpkin |
BP,S |
20-30,25 |
4 |
8 |
- |
|
Ridgegourd |
BP,S |
30 |
4 |
14 |
- |
|
Snakegourd |
S |
30-35 |
- |
14 |
Dark,GA3 500 ppm 24hrs Remove seed coat |
|
Watermelon |
BP,S |
20-30:25 |
5 |
14 |
- |
|
Brinjal |
TP,BP |
20-30 |
7 |
14 |
- |
|
Chilli |
TP,BP |
20-30 |
7 |
14 |
Kno3 |
|
Bhendi |
BP,S |
20-30 |
4 |
21 |
- |
|
Tomato |
TP,BP |
20-30 |
5 |
14 |
Kno3 |
|
Onion |
TP,BP |
20-15 |
6 |
21 |
Prechill |
|
Amaranthus |
TP |
20-30 |
- |
8 |
Light |
|
Coriander |
TP,BP |
20-30,20 |
7 |
21 |
- |
|
Spinach |
TP,BP |
15-10 |
7 |
21 |
Prechill |
|
Carrot |
TP,BP |
20-30,20 |
7 |
14 |
- |
|
Radish |
TP,BP |
20-30,20 |
4 |
10 |
Prechill |
|
Turnip |
TP |
22-30,20 |
5 |
7 |
Prechill,Kno3 |
|
Field bean |
BP,S |
20-30,25 |
4 |
10 |
- |
|
Cabbage |
TP |
20-30,20 |
5 |
10 |
Prechill,Kno3 |
|
Knol-Khol |
TP |
20-30,20 |
5 |
10 |
Prechill,Kno3 |
|
Cauliflower |
TP |
20-30,20 |
5 |
10 |
Prechill,Kno3 |
|
|
|
|
|
|
|
NOTE: (1) Prechilling: The replicates for germination are placed in contact with the moist substratum and kept at low temperature(between 5° c and 10° c)for upto seven days for all agricultural and vegetable seeds.
(2) Potassium nitrate(Kno3): Instead of water 0.2%Kno3 Solution (prepared by dissolving 2g Kno3 in one litre of water) is used to saturate the germination substratum at the beginning of the test. Water is used for moistening thereafter.
(3) Gibberellic acid(GA3): Required concentration should be prepared. For preparing 1000ppm solution dissolve 1gmGA3 in 1000ml of water, for 500ppm dissolve 500mg in 1000ml of water and for 100ppm,100mg should be dissolved in1000ml of water. When concentration of GA3 is not mentioned ,any concentration ranging from 100 to 500ppm should be used. Seeds should be soaked in required concentration of GA3 for 17hrs at room temperature, dried on the laboratory table and put for germination.
The seeds arranged in replicates are tested under favorable moisture conditions and in accordance with the methods prescribed in the above Table. After the period indicated in the table the replicates are examined and counts are made.
General
Requirements for Germination
Seeds require certain conditions for normal germination. The most important requirements are substrata, moisture, temperature and light.
Suitable substratum
The substrata serve as a moisture reservoir and provide a surface or medium for which the seeds can germinate and the seedlings grow. The commonly used substrates are paper, sand and soil.
Paper substrate
Most widely used paper substrates are filter paper, blotter or towel (kraft paper), these are easy to handle versatile and comparatively cheap.
Sand
It may be necessary to wash and sterilise the sand before use. For reuse of sand it must be washed, dried and resterilized. Sand which has been used for testing chemically treated samples, should preferably be discarded without being reused, if however, it is reused it should be ascertained that chemicals which may have accumulated in the sand do not cause phytoxic symptoms.
Soil
Soil should be of good quality, non-caking and free from any large particles. It must be reasonably free from weed seeds, bacteria, fungi, nematodes or toxic substances, which might interfere with the germination of seeds, the growth of seedlings or their evaluation. Soil should allow adequate aeration for germination when water is added with a pH of 6.0-7.5. Before use soil may require sterilisation and soil is not recommended for reuse.
Specification of
Germination paper:
Germination paper should preferably possess a creaped surface. The paper should have an open, porous formation and he free from impurities or toxic substances that may affect seed germination. It should be free of fungi or bacteria which might interfere with the growth or evaluation of seedlings. It should hold sufficient moisture during the period of test and should possess sufficient strength to resist wear and tear during handling. The texture should be such that the roots of germinating seedlings will grow on and not into the paper.
The paper shall meet the following requirements.
|
Type of Paper |
Basis Mass (g/m2) |
Bursting Strength (kg/cm2) |
Capillary rise (in mm). Min |
PH |
Ash, % by mass (Max.) |
|
Filter paper |
130-135 |
1.0 |
30 |
6.0 to 7.5 |
1.20 |
|
Towel paper |
95-100 |
2.0 |
30 |
6.0 to 7.5 |
1.50 |
In this, test, comparison shall be made between germination papers of unknown quality and known acceptable quality. Pieces of paper should be cut to size and placed in petridishes or plastic boxes. Petridishes or plastic boxes should be lined with two thickness of such paper. The papers should be saturated with tap water and seeds of Brassica species or onion should be germinated. Evaluation may be done by comparing the development of the seedlings grown on unknown quality of paper and those grown on the known quality of paper. The evaluation of seedlings shall be made after 3 days in case of Brassica and after 6 days incase of onion. If paper of unknown quality contains toxic substances, the root tips will be shortened and sometimes discoloured, root hairs ‘bunched’ and sometimes plumules shortened.
Determination of
Capillary Rise
Cut ten strips of paper each 10 mm wide, five in the machine direction of the paper and five in the cross-machine direction. Immense each strip in distilled water at 27 ± 2 °C to a depth of 20 mm at the end of the strip. After 2min measure the height to which the water has risen in the strip, to the nearest 1 mm. Calculate the average of the 5 strips in the cross machine direction. The lower of these two averages shall be taken as the result for the test.
SPECIFICATION FOR
SAND
Sand shall be clean and free from clay like material dirt, crushed stones or pebbles. The particle size of the sand shall be such that whole of the material shall pass through 850 micron IS sieve (aperture 0.85 mm) but shall be retained on a 45 micron IS sieve (aperture 0.045 mm). It should not contain toxic materials to cause injury to seedlings. The pH should be within the range from 6.0 to 7.5. The specific conductance should be within the range from 0.01 x 0.02 ms/cm2.
Biological Test for
Toxic Materials:
In this test, comparison shall be made between sand of unknown quality and sand of known pre tested quality. Sand should be placed in petri dishes or boxes to form a uniform layer 2 cm deep. It should be moistured to its 50% water holding capacity, Seed of onion or Brassica species should be placed and cover to a depth of 1 cm of moist sand. Evaluation may be done by comparing the development of the seedlings grown on the unknown quality and those grown on known quality as described for testing the germination paper.
Storing of Samples
The official samples after testing should be stored in controlled storage (3