Re: Observations on seed treatment with NaOCl


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Abgeschickt von Peter Corkhill am 03 November, 2003 um 14:44:16

Antwort auf: Observations on seed treatment with NaOCl von Michael Weinert am 30 Oktober, 2003 um 06:22:09:

Michael, regarding your first conclusion I am sure you are right that a small quantity of seeds in a large volume of bleach solution bleach a lot faster than a larger weight of seeds in a smaller volume of bleach of the same concentration. I am also prepared to believe that the action of the bleach will be fiercer in the first situation. This means that just asking someone “how long do you bleach the seeds of Cypripedium x” produces a pretty useless answer unless you know the amount of seeds and the volume of the bleach, as well as its strength. Although I don’t have any scientific evidence to support this view it comes from just watching what happens in practice as the colour fades in different bleaching situations. Because of this, for my own purposes, I have tried to standardise my bleaching over the years and always use 20ml of a standard strength solution and fill the tip of the same micro-spatula, to measure out the seeds. I would weigh the seeds but normal mortals do not normally have access to such an accurate balance, as they are very expensive and usually only in universities or research establishments.

Your second conclusion, that there are at least two different types of seeds in the same pods and there exists a type that needs little if any bleaching, also comes as no surprise. I attended a lecture several years ago in London given by Marilyn Light about her work germinating Epipactis helleborine seeds in Canada. She also found two types of seeds, one that germinated readily when the seeds were very fresh and another that were very difficult to germinate. I remember suggesting from the floor that this could well be a plant strategy evolved to exploit situations for immediate germination and dormant seeds for long-term storage/survival. I felt my suggestion was not taken very seriously at the time so I was amused that you came to a similar conclusion. I have noted that even when sowing green pod seeds that not all jars from the same pod germinate equally and concluded that seeds from different parts of the pod get sown into jars with their immediate neighbours. In fact you can often see that seeds in one part of the pod are loose and fall out, while at the other end seeds are less well developed and have to by teased out.

Perhaps when you noted two types of viable seeds, it is just a reflection of this differential development within the pod. The first seeds to develop will have more time to accumulate the dormins that inhibit germination but the last to develop will have a lot in common with green-pod seeds, which will germinate with no direct bleaching at all.

Does this help us to germinate Cyp seeds? I am not sure but greater knowledge of the subject would certainly be an advantage, it would make an excellent student or research project! But I am too long in the tooth and prefer in any case to take the easy way where possible and germinate green-pod seeds. However, I have noticed that occasionally when I have got the timing wrong and sown seeds I judged to be too old for green-pod culture, some germination occurred anyway – so maybe you are right and the feature occurs in Cyps too.

Peter




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