ac25 at cornell.edu
Mon Jul 12 20:19:59 EST 1999
No. Julias right.
Cauliflower is highly divided meristematic tissue. If you look at
sections in publications the two are indistinguishable in structure. Look
for articles by June Medford who has used this botanical oddity to obtain
large amounts of meristematic tissue to identify meristem specific genes.
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
> 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?
> 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".
> 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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