Very true. And it indeed happens. The question relates as to why there
are so many of these crosses produce tetraploids. The number of
unreduced gametes is small, yet their percentage of success is much
higher then the haploid gametes which outnumber them by a huge amount.
Thus something must be going on that gives the unreduced gametes a
biological advantage.
Chuck Chapman
--- In iris-species@yahoogroups.com, David Ehrlich <idavide@...> wrote:
>
> There doesn't seem to be any a priori reason why the haploid pollen
tube shouldn't reach the ovule to fertilise the diploid ovum.
Similarly, there's no reason why the resulting triploid zygote should
not be viable. It would be sterile, but it might still be a vigorous
plant.
>
>
>
>
> ________________________________
> From: irischap <irischapman@...>
> To: iris-species@yahoogroups.com
> Sent: Thursday, December 11, 2008 9:01:19 AM
> Subject: [iris-species] Re: HYB: diploid - tetraploid crosses
>
>
> An interesting question. Some of the literature on plant Physiology
> may have some good information.
>
> A speculation is that the pollen tubes of the diploid pollen are
> larger and probably more vigorous then their monoploid brethren. At
> least the pollen tubes would be larger and have more of the cell wall
> precursors and be better able to dissolve tissue as they grow down the
> style. In tetreaploids the style will be longer then diploids, so
> farther to go, so many monoploid pollen grains may not be able to go
> the distance.
>
> Just some speculation.
>
> Chuck Chapman
>
> --- In iris-species@ yahoogroups. com, Bill Chaney <billchaney@ ...>
wrote:
> >
> >
> >
> > Since I have not seen any posts for a couple days, thought I would
> ask a question I have been pondering for some time. These winter days
> give me time to poke around the web and do a little on-line library
> research.
> >
> > I am also cross posting to iris-photos and iris-species. If that is
> not appropriate, my apologies. I am new to both groups. My
> observation is that iris-photos seems to be mostly TB breeders and the
> iris-species group has a somewhat wider interest. Is that accurate?
> I know many of you will get this twice. Sorry.
> >
> > So my question is: In making crosses of diploid and tetraploid
> plants, my understanding is most people use the diploid pollen on
> tetraploid pod parents because some of the pollen cells may be diploid
> (unreduced) giving rise to viable tetraploid seed. There seems to be
> some good evidence of this happening in the literature in a variety of
> plant groups. (One of the advantages of being emeritus from the
> University is that I still have electronic library access.) So what
> happens to the all the reduced pollen? Does it germinate and produce
> pollen tubes, but just not result in viable gametes? In some cases I
> know triploid plants are produced, but these seem uncommon in iris.
> Is that true? Any suggestions for some good cold night reading on the
> subject?
> >
> > Thanks
> > Bill
> >
>
