North American Fruit Explorers mailing list at ibiblio

[Tom Olenio <tolenio@sentex.net>]

Hi,

Did some quick research and it is ABA not IBA, which keeps seeds dormant.

=============
http://csm.jmu.edu/biology/mcmullck/class/topic20.html

ABSCISIC ACID

This is a GROWTH INHIBITING HORMONE. It was first noticed in the
dormant buds of ash and potatoes. Application of ABSCISIC ACID (ABA) to
vegetative buds changes them to winter buds by converting the leaf primordia 
into
bud scales. Its inhibitory effects on buds can be overcome by gibberellin. 
There are
currently no practical uses for abscisic acid.

GIBBERELLINS

More than 80 gibberellins have been isolated and identified chemically. The 
best
known is GIBBERELLIC ACID (GA3), which is also produced by the fungus
GIBBERELLA FUJIKUROI (foolish seedling disease on rice). These hormones
have dramatic effects on STEM ELONGATION (BOLTING).

The highest concentrations of gibberellins are found in SEEDS. In many plants,
gibberellins will SUBSTITUTE FOR THE DORMANCY-BREAKING COLD
OR LIGHT REQUIREMENT and promote the growth of the embryo and the
emergence of the seedling. They do this by stimulating cell elongation, which 
causes
the root to penetrate the seed coat or fruit wall.

Application of gibberellins to rosette-forming plants can cause them to FLOWER
even without their appropriate temperature or light requirement being met.
Gibberellin can thus be used to produce early seed production of biennial 
plants.
==========

But I think my WAG still applies, regarding the GA3 possibly breaking the 
chilling
hours.

If you notice, it says there is currently no use for ABA.  I wonder if it 
would be of
use in seasons where cool winter weather  is too slow in coming.  If you began
spraying ABA when colder weather "should" be starting, maybe you could 
prevent losses
due to a sudden seasonal change, happening very late in the season.  Sort of 
telling
the plants to put on their winter coats.

I know some people felt that the sudden winter last season killed off some of 
their
vines.

Just a thought.

Regards,
Tom

Thomas Olenio wrote:

> Hi,
>
> I have read two different reasons for seed dormancy;
>
>   * embryo finishes developing
>
>   * chemicals inside the embryo need to break
>     down to break dormancy
>
> If I recall properly, IBA (rooting hormone) is present in the embryo, and
> not until the IBA breaks down will the seed germinate.  Cold must help
> break down the IBA.
>
> So if you apply this to chilling hours...  (educated guess on my part)
>
> If the same situation holds true for limbs of trees (they do not leaf out
> in spring until IBA levels drop in the buds), then would GA3 (gibberelic
> acid) help to break the limb dormancy (chilling hours)?
>
> Would a spray or two of "tomato set" (GA3) help these under chilled
> grafts to bud out?
>
> Thanks,
> Tom
>
> --
> Thomas Olenio
> Ontario, Hardiness Zone 6a
>
> On Tue, 12 Jun 2001, Ed & Pat Fackler wrote:
>
> > Greetings folks:
> >
> >      My 2 cents worth on chill requirements of various fruit species.
> > Some time around 20 years ago when I was stupid enough to believe all 
> > these
> > written facts, I did some playing around with seed germination in an 
> > unheated
> > basement and other situations.
> >      After some few years of various types, based on what I saw at this
> > constant 55 degree basement situation, the following observations were 
> > noted.
> >      1.  Chill time does accumulate at this temperature, but the 
> > accumulation
> > is much slower to occur (than the written "fact" stated).  Or, the 
> > implication
> > from this was that so-called "hours or time" is coupled or dependant on
> > relative temperatures during this period.
> >      2.  Subsequent growth appeared to be somewhat slower or the 
> > seedlings did
> > not exhibit normal vigor until the 2nd year in a nursery.
> >      3.  One fact was substantiated or appeared to be anyway.  That was 
> > that no
> > chill time accumulates at temperatures below 32 degrees or seeds simply 
> > are
> > suspended indefinately.  I put some in a freezer with a constant temp. of
> > zero.  I took them out a year later, stratified and most germinated.
> >
> >      Or, to quote the late Dr. Bob Lamb of Cornell, "the more I learn of 
> > these
> > facts, the less sure I am of them".
> >
> > Ed, So. Indiana
> > del stubbs wrote:
> >
> > > I dont know how to figure chilling hours ....we certainly had 4 months
> > > completely below freezing, much below 0. I'd say an absolute minimum 
> > > would
> > > be 3000 hours below freezing and probably a lot more. I'll call around 
> > > and
> > > see if there is actually some gov. agency that actually records such 
> > > info.?
> > > any idea where to learn the chill req. of manchurian apricot?  Mn. Del
> > >
> > > >From: "Kieran or Donna" <redherring@tnaccess.com>
> > >
> > > >The chilling hour clocks on stone fruits tick only between 34 and 45
> > > >degrees
> > > >(anyone want to fine tune my numbers, which are from memory).  Your 
> > > >trees
> > > >might have clicked off some of the time, but then you got them warm.  
> > > >they
> > > >stopped ticking.  They're like apple trees I have heard of in Florida 
> > > >that
> > > >went dormant, stayed bare a whole summer, and leafed out the following
> > > >spring.  Apricots in general have short chilling requirements, that is 
> > > >why
> > > >they do so badly for us with our mild southern winters.  They're 
> > > >likely to
> > > >bloom in Febuary here.   You may indeed have to chill your trees to get
> > > >them
> > > >to come out.  Maybe a block of ice wrapped up with the pots would do 
> > > >the
> > > >job.  How many hours in a week?  What do apricots generally need?  
> > > >500-600
> > > >hours?   Do you think you got half that much before you brought them 
> > > >in?
> > > >Donna in TN
> > > >
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--
Thomas Olenio
Ontario, Canada
Hardiness Zone 6a



 

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