Front Range Seed Analysts
1997 Seed Forum Volume 11 Number 2
THOUGHTS ON SEED GEMINATION:
HISTORICAL USE OF KN03
by Jim Bruce
USDA/ARS National Seed Storage
Lab
I just finished writing the Seed Germination and Viability Course for CSU Continuing Education, and I've been reviewing what I have written for my section of this correspondence course. I realize that there is much about seed germination which I have learned over the past 20 years of testing seeds or have experienced by watching Mother Nature at work in my garden and on my meadow that has not been included in the course itself. One of the problems with writing a correspondence course is that you have to stick just to the basics of the subject. In a classroom situation, you have the time to go beyond the written word and explore the subject, which you are teaching in more detail. You can even get sidetracked with little interesting tidbits and details which would be too lengthy with the written word. In writing a correspondence course, you don't have this luxury.
I thought that I should share a few of the germination tidbits, which I have wondered about and investigated in the past 20 years. I realize that this will take some space, so I will start with recent thoughts and progress backwards through a couple of issues of the Seed Forum.
Just recently, I was pondering why the AOSA rules recommended using KN03 for the germination of some seed species. I didn't know for sure myself. I had heard that the usage of KN03 came out of an experiment to see if fertilizers had a positive effect on seed germination. After "surfing" through the literature, all I could find mentioning early KN03 research was a reference to the 1938 AOSA Proceedings. This was an article on the germination of several native grasses and the research to have them adopted into the AOSA Rules for Testing Seed written by Vivian Toole of the USDA. In this article, Ms. Toole states that they used KN03 in the experiment because "the germination enhancing effects have long been known." There was no reference in her bibliography to KN03.
I started going backwards through the AOSA Proceedings and Newsletters. I found KN03 being used in referees and research, but no answer to the question - Why? In 1917 the research committee stated that experiments with seed germination should
Include both water and KN03 to determine if the KN03 would give better germination results. They believed that this should be done because "it has long been recognized that KN03 has beneficial effects on the germination of some species." Dr. E. H. Toole, Vivian's husband, was the chairman of the committee that year.
An interesting sidetrack on the Tooles. Both worked at the USDA Seed Lab in Beltsville researching seed germination methods. It is surprising how many of the species in the AOSA Rules comes from their investigations - many of the Poas, Festucas, Boutelouas, Eragrostis, and many more. Mainly grasses.
I still didn't know why we use KN03 and how it came to be known for such "a long time" that it gave higher germination percentages for some species. I ask Arnold Larsen. His answer, "We've always used KN03 whenever researching a species germination requirements, comparing the results with water. It's known that KN03 aids the germination of some species, especially those with light dormancy".
I still didn't know. I did know that the Tooles seemed to be promoting its use. I decided to follow the Tooles. Starting with the 1916 AOSA Proceedings I began going backward in time looking for articles by either one of the Tooles. Unfortunately there were none. It seems that 1917 was the first year that we hear from these two. I figured that if they were just getting into seed testing literature, they must have gotten their admiration for KN03 from someone. The logical place to look was their predecesor at the USDA. This was Bertha C. Hite.
Bertha first used KN03 on Poa compressa along with 13 other nutrient solutions to note their effect on the germination of bluegrass. This wasn't an original idea though. It seems that her investigation was sparked by Dr. H. Roiling in his 1912 dissertation thesis entitled: "Keimversuche mit Grasern our Ermittlung des Einflusses des Alter und Licht auf dem Keimprozess ausuben." In his thesis he tries various nutrient solutions with and without light to enhance germination of grasses.
Here at last we find the first official use of KN03. It should be noted that both Hite and Roiling found that other nitrate containing nutrients had a greater effect but KN03 was settled upon for general usage because of the profuse molds which developed on the seed test with other solutions.
This could be the end of the story but being who I am, I had to see if there was any basis for KN03 enhancing seed germination in the natural environment. Once again, surfing the literature I find that in the years 1990 through 1993 F.A. Bazzaz studied the relationship of ammonia (NH4) and nitrate (N03) in disturbed and undisturbed soil conditions with their effects on germination and subsequent plant growth. He found that the NH4/NO3 ratio increased favoring NH4 in undisturbed perennial fields. Disturbance of these fields by plowing shifted the ratio to favor N03. He likewise found a similar situation in forest communities. Interestingly, Bazzaz found that under lowlight situations, N03 supplied plants grew better than those supplied NH4. The opposite was true under conditions of highlight.
As for seed germination Bazzaz found that both summer and winter annuals were stimulated by N03. Perennial species which normally colonize established sites tended to germinate more readily in soils with a higher NH4 level. He concluded that most annuals and some perennials that normally colonize disturbed sites had evolved to germinate in the high N03 environment created by site disturbance. Unfortunately, Bazzaz did not look into the relationship of N03 and light dormancy as it concerns seed germination.
What can we conclude about KN03 and its use in seed germination? It seems that KN03 is a natural for enhancing seed germination because of the N03 ion that becomes available when in solution. This mimics a natural trigger for some species which, when other requirements like temperature and moisture are met, says "time to germinate". This would be the reaction in nature under disturbed soil conditions. It also enhances the light reaction in some species, especially in low light situations. It could be that in our germinators those species that have light responses to more intense light respond under our low light conditions by a KN03 enhancement.
We may have included KN03 into our testing procedures because of some old experiments to see if plant nutrients would affect seed germination, but isn't it nice to know that they do have a basis in the natural world for why they work.