Angelica research

This article was instigated by an initial study done to acclimatize the herb angelica archangelica into California. Angelica is native to high altitudes and high latitudes. In these rather harsh environments the demand made on the harvesting of the plant root has created a concern among plant scientists has put the plant on the endangered list. This in large part is due to the poor germination rate of the seeds. Much research has been focused on enhancing the germination rate so that the plant could be grown in large lots and reintroduced to its native habitat since it is a valuable medicinal plant. However, in doing research for this project the online abundance of the research led to many abstracts and articles on germination of the herb. As I collected these articles a pattern in the research itself began to appear that I thought would be interesting as the subject of an article in itself.

The research methods used to test germination rates of angelica revolved around several issues, chemical treatment of the seeds as a pre- soak, layering and refrigeration of the seed for chill requirement, quick loss of viability in storage, and the need for light to be involved in the germination process. I will outline the results of some of these various approaches using information from the various abstracts so that a persistent hidden pattern in the research protocols can be revealed.

Chemical pre-soak

In the first article on angelica germination in the American Journal of Science these researchers focused on the use of three chemicals, potassium nitrate, sodium hypochlorite and thiourea. This comprehensive project also compared polyhouse, open nursery bed and laboratory germination rates. Laboratory seeds were surface sterilized with mercury chloride and germinated in glass dishes on filter paper. For viability seeds were layered in polythene bags at low temperatures 39°F and room temperatures 70°F for shorter or longer times to test for length of viability, moisture imbibition and chill requirements of seeds. Germination rates were tested with seeds from four different natural populations. Tests of viability at different harvest sites showed a wide range of viable seeds between the different sites. These differences became more pronounced when the responses to the different populations became specific to particular seed soaks. Seeds from one population had greater germination from soaking in sodium hypochlorite while seeds from another population manifest minimum germination from soaking in that chemical. The thesis drawn from these procedures was that perhaps the chemical forms of nitrogen caused a “shift in the respiratory metabolism of the pentose phosphate pathway”. The conclusion was that different populations respond differently to plant regulating substances.

This idea was enhanced when there were very fluctuating  results from the chemical pre-soaks in the field trial plant groups. Some groups favoring one or another chemical seed soak and seed depth for sowing. The conclusion from this work was that the presoaks are helpful in reducing germination time for angelica seeds but the results are specific to the particular population.

The next article on seed soaking describes the use of KOH or potassium dioxide (lye) as a seed soak.  This article gave parts per million dilutions for the KOH and timing in minutes for the seed soak to achieve maximum germination. The idea here was that alkaline solutions are effective solvents for the protective barriers that plant seeds use to guard against moisture penetration that causes premature germination. This article concluded that KOH was a universal agent in enhancing germination in hard to germinate seeds.

There was a short paragraph citing the possible influence the position of the seed on the mother plant had on the potential for germination.

Still dealing with the seed soak approach, the next article described experiments with seed soaking and photoperiod of angelica. This article refers to GA or plant growth regulator (gibberellic acid) as a means for enhancing germination. It also addresses the use of dormant stratification of seeds in refrigerated conditions as a way of maintaining  viability. Even with the framework of the addition of these chemical substances there was an underlying theme in several of these articles pointing to the differences that exist between the different populations that produce the seed.  Since the seed soaking didn’t seem to be a conclusive outcome I decided to go over the articles again to see if there was any other avenue of research.

More careful reading of the first article revealed, buried under descriptions of chemical seed soak interactions, a short paragraph citing the possible influence the position of the seed on the mother plant had on the potential for germination.  That put the focus away from chemicals to the concepts familiar to plant morphology and led to a source cited in that article.

Plant morphology

This source was a game changer for me since it was written as a summary of the seminal works of Baskin and Baskin on seed morphology.

The general point of view of these respected researchers is that it is the mother plant and not the embryo itself, that determines the resistance or susceptibility of the embryo to the process of germination. That is,  the last growing season creates patterns of substances in the mother that determines the germination potentials of the embryos in the seeds of the next generation. Here is was not simply a matter of seed soak chemistry but of a kind of morphological inheritance or memory that could begin to explain why the different populations had quite different potentials for germination.  In a word it suggested that what the wine growers call “terroir”.

Terroir is a term describing the development of phenotypic based on the accumulative forces of not only the plant variety itself but also the soil type, the climatic niche, and even the particular growing conditions of one season that go to make up the profile of successful or not successful vintages. What if the terroir enabled the mother plant to confer qualities on the seed that gave it a kind of primer for how to behave in the next growing season? This direction could be taken even further in considering a more direct role of the mother plant. A question arose as to whether the germination variations in different populations could be influenced by the condition of the seed at harvest time.  Could it be that the terroir of one locale dictated a different set of instructions into one population in one year than in another population in a different locale and that these influences came to a head when the seed was harvested and taken from the mother plant?  A search for harvesting parameters for angelica seed led to the following paper.

This research took the work of Baskin and Baskin to a logical end by observing the difference in the seed viability of seed taken from three different sites on the plant itself. Being a biennial and an umbel bearing plant, angelica bears fruits on the ends of elongated seed stalks that rise from the central root in the second year. A vigorous growth will produce several umbels around the primary umbel. The indications in this paper stated that seeds of angelica taken from the primary umbel of the plant showed heightened potentials for germination while seeds taken from a secondary umbel showed far less viability. Could this be the source of the variation in population differences seen in the other research? Remember that the differences showed up even when the same seed soak chemicals were used on the different populations.

To take this line further in botanical taxonomy angelica archangelica is andromonoecious. The following site explains the difference in seed structure from the same plant.

All flowers of the primary and secondary umbels are bisexual, or secondary umbels have both bisexual and male flowers. Seeds from primary umbels have a significantly higher germination rate than seeds from secondary umbels; many of the seeds that do not germinate lack an embryo . Andromonoecious means that in general the primary umbel has florets that are both male and female, that is they are complete flowers like those found in the composites. However, the florets of the secondary umbels, depending upon the stressors found in the circumstances of growth may be complete flowers that are both male and female or entirely male. Male flowers will have a vestigial seed with no embryo.

Summary

If we  step back now and take a survey of these various research parameters it can serve as an instructive overview of the need to keep  pushing through accepted goals and expectations for the experimental work to see if further horizons of influence can be observed. The initial studies cited here focused on chemical seed soak as the goal of the research with the focus of finding through experiment the most effective chemical for breaking down seed or embryo resistance to  germination. Then when the chemistry was found to be effective to a certain degree in one population but not to the same degree in another population the search needed to be broadened to seed morphology and the action of the mother plant on the germination rate of the seeds.  This then led to the morphology of the plant itself and the influence on the placement of the seed head on the plant as an indicator of viability.

It might be possible in a Biodynamic framework to include here the position of the moon with regard to the timing of the seed harvest and the sowing of the seed for the purposes of the germination experiment. Of course this would stretch the issues of the viability of angelica archangelica seeds into uncharted territory for contemporary science. However, it is presented here as a potentially valid avenue for research since it appears that, even in well conducted scientific experiments it seems that what the researcher is searching for is what shows up as the outcome of the research.