Front Range Seed Analysts
1992 Seed Forum Volume 6 Number 3
THOUGHTS FROM THE FRONT RANGE
by Jim Bruce
This is a time for reflection on seed testing. Many of us continually
go through periodB Of self doubt as to why we are in this field, what does
it all mean, and are we actually doing anyone any good? I personally don't
feel alone when pondering these questions. I have yet to meet a seed analyst
who doesn't feel some misgivings about their choice in occupation or their
field of work. This is particularly true if you are a germination analyst,
as I am presently. The meetings give us a chance to visit with other analysts,
discuss problems we see, initiate new directions in the testing of seed,
and re
affirm our worth as competent analysts.
The germination analyst has a particularly hard spot in the field of seed testing. The seedsman needs this information for labelling and the germination test is what the grower associates with the quality of the seedlot. Yet, the seedsman and grower alike only want to hear the good side of the story, not being gracious for information which you see as betraying problems inherent within the that particular seedlot. Any problems have to be the fault of the analyst, not the seed or the person growing and conditioning them. I'm not discounting the fact that many of the questionable results of germination testing do stem from the analyst. In fact, this has been one of my pet projects over the years of being a seed analyst; determining the variation caused by the seed analyst and the interaction of the analyst with the test. But,.this is one of the reasons for having seed testing associations like the AOSA and the SCST, to minimize the subjective human input and make more objective evaluations of the data.
Seed germination has many problems. (I'm not saying that purity doesn't) . Germination isn't as standardized and is very subjective in its interpretation as we can all attest to. Many of our self doubts as to this occupation stem from our experiences with seed germination and whether anyone cares about the information which we can aquire from the germination test and its variations.
Sometimes, I would like to think of seed germination as this grand scientific endeavor that, like science should be, is straight forward and based upon sound scientific principles. But, I've been in the business too long. This is a subjective test. Actually, I knew this long before I gained entrance into the seed testing field. We are dealing with a living commodity. As with all life, nothing is absolute and we see the variations implied within populations, environments, growing seasons, and the individual as it reacts of the stimulii of life around it. Because our tests are subjective, we have to use the science of how Beeds germinate and grow in a loose manner, especially when trying to make an approximation of how the seeds will react in the field. In other words, as an educated guess.
The Association of Official Seed Analysts recognized this and set forth
to standardize the practice of germination testing. I see four principles
of
germination testing that they worked with in those early years
of seed testing. Many of these principles are still being worked on today
and evolve with seed testing as it meets the demand for the future. First,
the ASOA began work on methods to obtain simple germination of the seed
itself. What are the optimum temperatures for germination, how do we break
dormancy of otherwise viable seed, what do we do with those seeds we can't
get to sprout even after dormancy breaking procedures have been applied.
Second, how do we classify those seedlings which have germinated as to normal and abnormal growth. Most analysts would agree that this is one of the major areas of subjectivity in the testing procedure and causes some of the greatest descrepancies within and between laboratories. The AOSA is still addressing this and the publishing of the new seedling descriptions won't put an end to the controversy.
Third, the early analysts not only wanted to know how to get the seeds to germinate, but realized that each laboratory is a unique situation and the tests needed to be standardized in a manner which permits the duplication of test results between laboratories. I'll address this one and expand upon it in just a minute.
Lastly, our forefathers, (and .foremothers), of seed testing realized that even with research and rules concerning the above topics, this still is a very subjective test and certain limits of variation had to be accepted. Thus, came our statistical tolerances.
Germination testing has progressed and is still in evolution. Germination testing changes with germination problems to meet the demands of the seed trade. New crop species and cultivars tax our knowledge of germination and how to achieve the results which are expected of us as analysts. New harvesting and conditioning practices influence our germination tests and add frustration, yet excitement to what we thought was standard procedure. And let's not forget Mother Nature. She constantly changes the climatic conditions of the growing seasons and the physiological conditions of the seeds grown under her variability so that each year presents us, as analysts, with "seed problems" which have to be addressed.
Standardization still plagues us. This can easily be seen in our yearly referee tests. Reading the AOSA Rules for Testing Seed, one would think that methods for testing species are fairly standardized. Much research has been put forth by seed scientists toward standardization. Medias were looked into and studied for their seedling response, toxicity, and water holding capacity. Through these studies, we have come up with our towels, blotters, and kimpac which we accept for germination purposes. when the Rules state B,T,P for the substrata, we know that each of these media will supply us with an equivalent germination percentage within statistical tolerance of each other. This gives laboratories and seed analysts a choice of material which will fit into their laboratory requirements of cost, ease of handling, space requirements of their germinators, and availability of the media.
But other variables are harder to define and standardize. Temperature, moisture, light, count days, etc. are more elusive. I remember back to my junior high school biology days, studying seeds and plants for the first time and planting corn and garden beans around the outside of a jar to watch them grow and develop. We learned that there are three variables which affect seed germination: 1)temperature, 2) moisture, 3) and air, (of course I know now that some seeds have a fourth variable, light). The media was easily standardized as it is not a factor affecting germination, although it does affect the appearance of the seedling. it is these other variables which the seed analyst has the most control over and are the harder to standardize.
Temperature is controlled within the seed lab by the germinators. One would think that if you have a reliable germinator the problem of temperature is pretty much taken care of. But the optimum germination temperature is probably more evasive and variable than we realize. One only has to survey the various research on germination temperatures or view the variety of methods submitted as optimal, or best, for the AOSA publication on methods for germination of species not in the Rules. Optimum germination temperature is influenced by a number of factors including the cultivar, age of the seed, light, KN03 and other promoting chemicals, and pretreatment to name a few.
Moisture and air are my pet peeve germination variables. Air is fairly straight forward if you are dealing with ambient air as your source. It is the relative humidity.of the air which is much harder to control. But the moisture level of the media affects the germination of the seed as well as the air, or lack of it. Moisture is the one variable which the individual seed analyst has the most control over and also contributes, in my mind, the most variation between analysts and laboratories. The AOSA "thumb method" is quite vague and allows the analyst leeway for sloppy procedure. The Canadian seed rules at least have attempted to define some guidelines for properly moistening media. For paper towelling they recommend weighing the towels and adding moisture until the towel mass with water comes to a weight three times the weight of the dry towels.
The moisture level controls aeration to some extent. Too moist media at planting time forms, a film over the seed and cuts off the oxygen supply, thus making for sluggish germination or outright death of the seed. Treated cereals have also been known to be adversely affected by high moisture levels. The treatments are very hydrophyllic and attract water, cutting off the aeration which the seed needs to germinate.
Legumes with thin seedcoats, (soybeans, etc.), are subject to water imbibition damage by being placed upon too moist a media. In this case, water is taken up too quickly causing stress between the tissue layers of the seed. The resulting seedlings show abnormalities similar to mechanical damage such as broken and cracked cotyledons, cotyledon separation, and breaks along the embryonic axis.
Another problem with over wetting our media is evaporation. I remember one "carryover" cereal sample which I was having problems germinating at the usual 20C. As you know, the temperature of germination becomes more critical as seed is aged. The range of germination temperatures for fresh seed 1B quite wide and beyond the optimum, but the longer you store seed, the more the range narrows towards the optimum. Experimentation with this sample showed that it' preferred 25C over 20C. It took me a while to figure out that evaporation was the problem and the actual media temperature was 20C. Cereals also may display what is known as "water sensitivity" under high moisture regimes. This is a type of dormancy most of us have little understanding of.
With the AOSA/SCST Meeting being held here next year and all of the talk of standardization and harmonization, I hope that the above thoughts have prompted a little of your brain power on these lines. Just remember, the Rules and regulations under which seed testing work has been performed over the past 120 or so years have been developed and formulated to meet specific needs of the seed industry and have beed changed and redeveloped as conditions have changed and situations have demanded. Yet many of the basic problems of seed testing still exist and need to be readdressed as our seed trade becomes more and more international.