Date: 9 May 1995 09:33:09 -0500
Sender: "Mark Sorrells" (mark_sorrells@qmrelay.mail.cornell.edu)
Subject: Preharvest Sprouting & dormancy
Reply to: Preharvest Sprouting & dormancy
For those interested in grain dormancy etc., the 7th International Symposium
on Pre-Harvest Sprouting in Cereals will be held in Japan on July 2-7.
If anyone is interested I would be glad to send our abstract. This is the
title: QUANTITATIVE TRAIT LOCI ASSOCIATED WITH PREHARVEST SPROUTING
RESISTANCE IN WHEAT
M.E. Sorrells & J.A. Anderson, Dept. of Plant Breeding, Cornell University,
Ithaca, NY 14850; Plant Sciences Dept. North Dakota State University, Fargo,
ND 58105
Mark Sorrells
--------------------------------------
Date: 5/9/95 12:24 PM
From: Jack Dekker (jdekker@iastate.edu)
Subject: Dormancy and Vigor
Hello Seed Biology List People,
Here is a question that has occupied several of us in my lab for
some time recently, that I would like to have feedback, opinions,
(Articles?), etc. about. I will phrase it in terms of an hypothesis:
The physiological systems that control the seed behaviors of vigor and dormancy are qualitatively the same, but only differ quantitatively.
Any comments?
Jack Dekker (jdekker@iastate.edu)
Iowa State University
3218 Agronomy Hall
Ames, Iowa 50011
TEL: 515.294.8229
FAX: 515.294-3163
-------------------------------------
Date: 9 May 1995 14:28:13 -0500
Sender: "Mike Foley" (foley@btny.purdue.edu)
Subject: Dormancy and vigor
Jack - Your should talk to Eric Roos about your hypothesis. He might suggest to you that dormant seeds are actually low vigor seeds and afterripening increase their vigor. I do not want to put words in his mouth or take his comments out of context, so I will let you pursue it with him further. I do not think there is much in the literature directly related to your hypothesis but there maybe some papers that relate indirectly, and perhaps would give some support or direction.
On my recent quest to understand the basis for breaking dormancy by warm-dry afterripening I have read a lot of material. Some of the individuals/groups that may give you some leads are recent papers by Vertucci and Roos, Ellis and Hong, old and new papers from Leopold's lab, old and new papers from the Crowe's lab, anything that relates to seed aging/deterioration/longevity/sugars/ vitrification, anything on desiccation tolerance in biological organisms (Hoekstra's lab), etc. Good luck.
Mike Foley
------------------------------
Date: Tue, 09 May 1995 14:56:56 MDT
Sender: Bruce Maxwell (ussbm@trex.oscs.montana.edu)
Subject: Dormancy
Seed biology subscribers,
I am a plant population ecologist working primarily on weeds in small grain production systems of the Great Plains. My group has been conducting research for the past 3 years on the impact of parent plant environment at the time of seed maturation, on seed viability, germination and dormancy in wild oats. We have consistantly measured lower viability and higher dormancy on seeds maturing in the crop canopy understory. We think that maybe a fungus or bacteria could be involved in the observed response. Has anyone else observed similar phenomena or have ideas about the fungus or bacteria hypotheses?
Bruce Maxwell
Montana State University
------------------------------
Date: 10 May 1995 10:04:14 -0500
Sender: "Mike Foley" (foley@btny.purdue.edu)
Subject: Dormancy
Bruce - I have never paid any attention to the specifics of whether researchers have observed more dormancy in seed derived from wild oat plants in the understory. However, there are numerious references in the literature from many years ago to the present, and from numerious researchers that dormancy in cereal seeds including wild oats is greater if conditions are cool, moist during development. Several researchers have also demonstrated the depth of dormancy can be increased by growing the plants under reduced photoperiods. For example 8 vs 16h light. The question that comes to mind is, are the environmental conditions in the understory different (cooler, more moisture, less light) than above the crop canopy?
I have never seen anything in the literature relating the depth of dormancy to association with microorganisms during development. My guess in there could well be a rich microflora associated with developing wild oat seeds and it would be worth exploring your hypothesis. There was a symposium in Canada in ~1983 on wild oats. Someone at that symposium (I don't recall the name) presented a paper on microflora associated with wild oat seed (in the soil?). There probably was a proceedings from that meeting and it might be found in some library somewhere.
Mike Foley
------------------------------
Date: Wed, 10 May 1995 10:53:00 -0700 (PDT)
From: "Pallais, Noel" (N.PALLAIS@CGNET.COM)
Subject: Dormancy
I am probably the most pleased to join Seed Biology Electronic Conference. I have worked for 12 years with sexual potato seeds at the International Potato Center in Lima Peru, and it has been a lonely experience (lack of peer discussions) to work with the wild seed of a vegetatively domesticated crop.
My main interest is seed dormancy. My present endeavor is to domesticate "true" potato seeds by selecting "suicide" seeds (i.e. those that germinate readily after freshly-harvested under 27C). I welcome any questions, ideas, comments or suggestions. I need all the help I can get. This work was done 10,000 years ago for most of the seeds you are all working with.
I am also interested in other topics related to dormancy and domestication of true seeds, e.g. lack of seed deterioration when seeds are dormant, secondary dormancy, importance of embryo type other than seed maturity or incompatibilities??? etc. I am looking forward to learning and participating in this seed biology network.
Noel Pallais
------------------------------
Date: Thu, 11 May 1995 09:49:17 -0400
From: Prof Patricia Berjak (BERJAK@biology.und.ac.za)
Subject: Dormancy
Referring to your point about lack of deterioration when seeds are dormant, Villiers' proposal that, if hydrated, a dormant seed can carry out maintenance and repair function, is probably pertinent. A dry seed, on the other hand, will accumulate damage but cannot carry out repair processes.
Patricia Berjak
------------------------------------
Date: Thu, 11 May 1995 12:45:00 -0700 (PDT)
From: "Pallais, Noel" (N.PALLAIS@CGNET.COM)
Subject: Dormancy
Thank you Patricia. All I have is evidence that dormant true potato seeds retain optimum germination vigor when stored sufficiently dry under high temperatures provided we remove seeds from high temp soon after dormancy has been released. Our results suggest potato seeds begin to deteriorate under these conditions only immediately after dormancy has been lost. When seeds are stored dry deterioration begins slowly after dormancy is lost, but when dormant seeds are stored at above the critical moisture (5%) and at high temp, deterioration occurrs too suddenly and proceeds too rapidly such that we have never been able to catch them in time.
As I understand Villier's hypothesis, dormant seeds "do" deteriorate, but this deterioration is not evident because it repairs itself during subsequent hydration. I find this very interesting and quite important to our work because we are now recommending low moisture and high temperature to accelerate the rate of dormancy loss during afterripening in dry storage. I presume if deterioration happens, repair would not be 100%, which is what I feel we are getting when we stop high temp exposure in time.Though I was aware of Villier's work and conclusions, I must confess I never thought it might apply to potato seeds. In my mind, dormant potato seeds do not deteriorate until they lose dormancy, because they are in a state of homoestasis. I could be wrong!
Noel Pallais
---------------------------------------
Date: Fri, 12 May 1995 12:40:00 -0700 (PDT)
Sender: "Pallais, Noel" (N.PALLAIS@CGNET.COM)
Subject: Potato seed dormancy: Afterthought!!
Allow me a brief afterthought from my spurr of the moment comments in reponse to Patricia's suggestion about Villier's repair proposal vis a vis dormancy of "true" potato seeds.
Indeed, it seems evidence of deterioration which proceeds in slow motion when seeds are dry and "fast-forward" when moist, tends to disagree with the hypothesis that dormant seeds deteriorate except they have a more efficient repair system which is activated when seeds are hydrated again. Does my reasoning sound reasonable?
It is possible the dormancy mechanism of Villier's seeds is based on different inhibiting factors than those of sexual potato seeds. After all, dormancy is the effect; the causes might be physical or hormonal, or both (my feeling about potato seeds), and these factors might located in the testa, endosperm, embryo or in all three (Ibid). My observations lead me to suggest whatever different combination of dormancy factors different genotypes of potato posses (and the variability is tremendous in tetraploid progenies of potato which often vary at the species or sub-species level), inhibition is released with the same mechanism that causes degradation or aging (i.e. higher temp faster dormancy loss, etc.).
Noel Pallais
---------------------------------------
Date: Fri, 12 May 1995 16:43:07
Sender: R.H.Ellis@reading.ac.uk (Dr. Richard Ellis Agric Reading)
Subject: dormancy and vigour
Re discussions on dormancy and vigour
This is somewhat of a perennial issue. It is quite clear that dormancy and longevity in air-dry storage are often correlated, but the reverse can also be shown. Thirty years ago Professor EH Roberts showed that in that sense (and several others, eg Q10s) with studies in rice there was no causal relation between the two. I won't repeat those arguments here.
One further thought that occurs to me concerns phytochrome mediation of germination; clear in this case that the ler and the hir operate at different stages in germination and this plus cycling of inhibition and loss in dormancy (e.g. in Rumex) makes the story much more complicated than viability and vigour.
Clearly, in soil seed banks dormancy is the key to SEED survival (because if the seed germinates it is no longer a seed) but some of the comments in this correspondence about dormancy and longevity cannot prove anything (on grounds you can only disprove a hypothesis). Indeed those comments have been written in such a way as to suggest (by reversing the logic) that if dormant seeds die then there can be no link. There is indeed evidence in some species at least (especially those tree seeds which show considerable dormancy) that dormant seeds die even under comparatively benign conditions before losing dormancy but that non dormant seeds survive as seedlings.
The actual question raised initially concerns the physiology of the different processes; but isn't this a question we cannot answer until we know what each is?
I expect my argument also shows dangers of becoming circular.
Richard Ellis
The University of Reading, UK
---------------------------------------
Date: 12 May 1995 12:05:36 -0400
Sender: "Anwar Khan" (anwar_khan@qmrelay.mail.cornell.edu)
Subject: Seed biology research infor
You may be interested in knowing (and possibly attending) about the two important upcoming conferences related to seeds, etc.
1. Workshop on "Quantification of plant dormancy" on August 2 at the Amer. Society of Hort Sccience Meetiings in Montreal, Canada July 30 to August 2, 1995. Topis of discussion and presenters include: Quantification of seed dormancy-physiological and biochemical approaches by A. A. Khan, quantification of seed dormancy of deciduous orchard species by S.D. Seeley, quantification of bud dormancy-physiological approaches by L. H. Fuchigami a and Use of hormones and growth regulators in quantifying bud dormancy by Miklos Faust.
2. Crop Science Society Symposium on "Seed priming and synthetic seeds" on October 30, 1995 at St Louis, Missouri. Tentative topics and speakers are as follows: Overview of synthetic seeds, embryogenesis and practical issues by Dennis Gray, Synthetic seeds and desiccation tolerance by Bryan McKersie, seed priming and drying by Anwar Khan, Oxygen and loss of desiccation tolerance in submerged priming systems by Young Rog Yeoung and Dale Wilson, practical aspects of commercial seed priming with liqid carriers emphasizing research needs by Stuart Akers and practical aspects of commercial solid matrix priming emphasizing new possibilities by John Eastin.
Anwar Khan