Front Range Seed Analysts
1996 Seed Forum Volume 10 Number 2
THOUGHTS ABOUT SEED GERMINATION by James R. Bruce
A tour pauses at your workstation and observes you evaluating seedlings in the germination test before you. It is explained to the tour that you are counting the sprouts to determine the germination percentage of the particular seedlot as required under the Federal Seed Act and the State Seed Law. As the tour moves on, one of the members leans over and asks, "Is this all you do all day; count seeds?"
The experienced analyst knows the appearance of what he/she is doing reflects only a small portion of what the test is and the knowledge needed to perform the test. The germination test simplistically appears to be a matter of counting out seeds to plant and then, after the required germination period, counting the "sprouts" to find the germination percentage. Often it is felt that anyone can be brought into a lab and quickly trained to plant and evaluate the germination test. It is the purity analyst that requires intensive training, not the germination analyst. In reality, to properly perform the germination test one must have a certain knowledge of the parameters of the germination test itself, seed morphology, seed germination, and seedling evaluation. Coupled with this knowledge, the analyst must obtain a good deal of practical skill concerning the test and its evaluation.
The germination test is extremely subjective. To limit the subjectiveness of this test, the Association of Official Seed Analysts has continually updated their rules for planting and evaluating the germ test. This has led to a more standardized test procedure and through their referees has had the effect of making more repeatable results between laboratories. But test results do often vary and this creates problems with the selling of seed. Much of this variance comes from the lack of understanding of the test and the lack of background knowledge about the germination of seed.
A germination analyst must be as familiar with the purity rules as a purity analyst. This is especially true of the rules governing pure seed units. How can one plant a "germ only" sample without thorough knowledge of what is supposed to be planted? Think of the variance in results if one analyst is planting pure seed and another is just blindly planting from the bag of seed given them.
Problems arise from the beginning of the test if the analyst is not aware of the proper germination conditions of the test. Awareness of dormancy breaking mechanisms and especially moisture conditions of the test are extremely important to the end results of the test itself. I have seen, and obtained myself, large variations in results based upon the initial moisture level and with subsequent watering, or not watering of the test as germination proceeds. Understanding how different species react to specific germination environments allows the analyst to adjust conditions to the most optimum for the particular species being planted. It is my experience that many beginning analysts are given a general "cookbook recipe" for watering and planting a germ test which is supposedly good for all species. It is only when problems occur that the analyst realizes that a simple thing, as supplying moisture to the test, is more complex than thought. Some species react dramatically to the moisture level supplied.
A thorough knowledge of dormancy mechanisms allows the analyst to supply conditions or modify the seed itself to germinate more uniformly and rapidly. This same knowledge can lead the analyst to understand why the seed isn't germinating or how the analyst themselves caused the seed to enter into a secondary dormancy and prevent a good germination. I remember a time when an analyst had allowed a grass sample to dry out during the test period. He couldn't understand why the sample had such a low germination when the tag supplied by the company showed a quite high germ and the species was not known to have dormancy. After performing the TZ test on the remaining seed and finding them viable, he confessed to have let the test dry out, thus inducing a dormancy that normally wouldn't have existed. How could he have known? He was unaware of what problems the analyst can cause and the role the analyst has on the results of the test. He was simply told that you plant and water the test and the seeds germinate.
A sound training in the parameters of the germination test are extremely important to good test results. Knowing for instance that with some species, beans are a good example, rolling the towels too tight will produce normal seedlings that mimic abnormalities described in the seedling descriptions of the AOSA Rules. Abnormalities induced by the test conditions supplied by the analyst are more common than one would think. The AOSA Rules state that seedlings growing upside-down are abnormal. But if one is folding towels, you will find quite a few of these supposed abnormals in the folds when evaluating the test. These generally are artifacts of the test conditions supplied.
Training should include germinating the same seedlot on different media. This is very enlightening and one will come to a greater understanding of seedling evaluation when one realizes that the seedlings react and often appear different on different media. If you couple this with growing that seedlot in your garden, you gain much insight on how abnormalities react in the field. I have seen through AOSA/SCST referees how analysts see more abnormalities if they are grown and evaluated on a media not normally used by the analyst. Unfamiliarity with the reactions of seedlings to various media or the use of different media by two labs can cause a large gap in the results.
The concept of seedling abnormality has evolved with modern agriculture. Modern methods of planting and harvesting require uniformity of stand and maturation. Many abnormal seedlings will produce a strong plant but will delay maturation to such an extent that with a once over machine harvest, the yield will be lowered or quality will suffer. Our evaluation leans heavily to the economic side of agribusiness. The analyst must have a strong background in seed germination and seedling growth to produce results that have meaning to the consumer. An understanding of seed morphology and physiology give a foundation from which the analyst, through day-to-day experience evaluating seedlings, can gain an intuitive sense to the condition of the seedlot and how it may react in the field. It is this intuition stemming from experience that allows the analyst to overcome germination problems and leads to standardization of test results.
Seed morphology and an insight into dormancy is a must f or the interpretation of the tetrazolium test. Here again, experience must be associated with this knowledge. As with the germination test itself, the analyst must have a thorough understanding of the parameters of the test. Staining of the embryo does not always insure a normal germinating seedling. Of all the tests an analyst can perform, the TZ test is the most subjective. It is very dependent on intuition. This intuition stems from experience and knowledge.
What seems like a simplistic test at first glance can be seen to contain much background knowledge and training to properly perform. To quote an old saying, "You can have two analysts with ten years experience. One analyst may have one years experience ten years over and the other may truly have ten years experience." If an analyst prepares the test and evaluates it strictly out of the cookbook, without thought to the species or the end result or without background knowledge and experience, the test results will be merely a set of numbers without true meaning to the consumer. We must strive to be the latter type of analyst, constantly updating our knowledge and backing it with daily experience. We must also continue to educate the public and our customers to the service we perform and the knowledge we've acquired about seeds and seed germination.