sphinkson at worldnet.att.net
Thu Jul 15 02:55:30 EST 1999
A. Cary wrote:
> No. Julias right.
> Cauliflower is highly divided meristematic tissue. If you look at
> sections in publications the two are indistinguishable in structure.
> But if you stop looking in the book, and look at the plant, the stems (99% of the
> mass of the object of this discussion) you'll find already differentiated xylem,
> phloem, and support structure.
> for articles by June Medford who has used this botanical oddity to obtain
> large amounts of meristematic tissue to identify meristem specific genes.
Yes, this is the apex of a plant. You'll find meristem in the apex of plants !
> In plant development there is a transition from vegetative to floral
> identity in the meristem. This does not mean the cells are differentiated
> but rather that the developmental options for what the cells can become
> are restricted to bracts and flowers etc. The cells in the meristem are
> still proliferating and have not taken on their final fate, ie. are not
> differntiated. Sometimes under odd environmental conditions floral
> determination can be reversed. This condition is called 'floral
> reversion' and the meristem will start making vegetative organs again.
> But thats not very common. Cauliflower does eventually go on to
> differentiate into flowers and so the over-proliferation of the floral
> meristem is not a lethal condition.
> Meristematic tissue is considered to be undifferentiated but does still
> have an organization. Cells in culture that are loose and dissociate are
> called friable but they don't have to be friable to be undifferentiated.
> In old experiments, I can't remember who by, they could convert friable
> callus to more meristem-like orderly patterns by applying a slight
> pressure. But a young Cauliflower head is meristematic tissue.
> In article <37854229.243D933F at worldnet.att.net>, Steve Hinkson
> <sphinkson at worldnet.att.net> wrote:
> > Cauliflower is not "fleshy apical meristem tissue". Meristem is, by
> > undifferentiated cells. First, if it were meristem, all cauliflower
> would look
> > completely different (as does the undifferentiated cells grown for
> > mericloning). Second, it would as likely differentiate into new stems and
> > leaves as flowers. It doesn't.
> > This is the sort of academia that has discouraged me in the past. When you
> > don't cut and eat cauliflower, it blooms. Actually sorta' pretty for a cole
> > crop. So why should the bud clusters we eat be called mal-formed?
> They're just
> > juvenile.
> > Hypertrophied flowers? Cauliflower is flower buds, and the supporting stem
> > tissue. Some of my Orchids have been bred for hypertrophied flowers, and
> > cauliflower and broccoli have been bred for larger flower clusters, so the
> > preceding bud cluster will be larger too. I'll buy, as a definition,
> > "selectively bred hypertrophied flower buds".
> > *wink*
> > Steve
> > Julia Frugoli wrote:
> > > >At 12:07 AM -0400 7/9/99, David Hershey wrote:
> > > >>There does seem to be some controversy about whether cauliflower is
> > > >>really floral tissue. The Plant Science text by Hartmann et al. says it
> > > >>is "prefloral fleshy apical meristem tissue."
> > > >>
> > > >>A college Horticulture text says the edible part is "malformed or
> > > >>hypertrophied flowers" and "Hortus Third" calls it the "condensed and
> > > >>thickened malformed flower cluster."
> > > >>
> > > >>David Hershey
> > > >>dh321 at excite.com
> > >
> > > My understanding from the genetic work done in Arabidopsis and brassica is
> > > that
> > > cauliflower has been shown to be brassica with mutations in the the genes
> > > corresponding to the CAL or AGL9 gene and the AP1 gene in Arbidopsis. The
> > > CAL
> > > gene is a floral homeotic gene encoding a MADS domain protein homologous to
> > > AP1. It enhances the flower to shoot transformation in ap1 mutants, but has
> > > no visible phenotype when alone. Ap1 cal1 double mutants have inflorescences
> > > similar to cauliflower, resulting in a proliferation of apical meristem,
> > > making Arabidopsis look like cauliflower. So I think the short answer is
> > > the part of the cauliflower we eat isn't really a flower, just meristematic
> > > tissue.
> > >
> > > Julia Frugoli
> > > Department of Plant Pathology & Microbiology
> > > Texas A&M University
> > > Southern Crop Improvement Facility MS#2123
> > > College Station, TX 77843
> > > phone 409-862-3495
> > > FAX 409-862-4790
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