I thought I'd share a botanical oddity that falls into the category
of "things I probably wouldn't have believed without seeing for
myself":

Some researchers at a plant growth facility here have been growing a
very large number of corn plants, both from seeds and also many plants
derived from tissue culture. [The project is something to do with
developing pest and/or herbicide resistant strains]

Most are typical _Zea mays_ plants with a basically distichous alternate
phyllotaxy throughout, but individuals with aberrant leaf arrangements
also occur. When young, the aberrant ones seem at first glance to just
have rosettes with more rows of leaves than the usual two, but closer
inspection shows that they in fact consistently have a regular
opposite-decussate phyllotaxy. Older plants are more obviously opposite-
decussate, with opposite pairs of leaves alternating at right angles
and with opposite pairs of axillary "ears". The sheathing bases of the
pairs of leaves overlap one another [i.e, each is the 'outer leaf' on
one of the two margins]. The mature stems are more or less square. The
basal branches of the terminal male-flower "tassel" are similarly
opposite-decussate in arrangement.

I would estimate that between 1% and 3% of the hundreds of tissue-
cultured plants show this very strange [for corn, and for any member of
the grass family] phyllotaxis. They seem to be regularly produced in low
numbers.

Perhaps a closer study of the apical meristems and leaf primordia of
young individuals could be published, at least to document the existence
of this aberration. It may be of potential interest to any researchers
into phyllotaxy, if such still exist.

Does anyone know if this or similar oddities have been reported
before?

It seems likely to me that this isn't a new genetic trait, but is
perhaps just an alternative expression of the normal
phyllotactic-control mechanisms [whatever _they_ are] in a novel
setting without some of the normal developmental constraints acting
on an embryo forming in a seed. [Growing the seeds of these plants
will help show whether it is heritable, but I don't think this has been
done yet.]

cheers

This is interesting. Has anyone determined whether this leaf and/or ear
arrangement results in increased productivity?

M. Reed

"monique" wrote in message
...
This is interesting. Has anyone determined whether this leaf and/or ear
arrangement results in increased productivity?

Well, I do get the impression they have more leaves than normal.
[Perhaps twice as many?] Yours is an interesting question, but so
far as I know this phenomenon hasn't been reported or studied
before...

cheers

"mel turner" schreef
Well, I do get the impression they have more leaves than normal.
[Perhaps twice as many?]

***
If they have twice as many leaves as normal, maybe it is not that the leaves
have an unusual position, but that the leaves have their normal postion, but
twice in each position?
PvR

In message , mel turner
writes

Does anyone know if this or similar oddities have been reported before?


Before I chime in, are you interested in aberrations in corn, in
Poaceae, or in general?
--
Stewart Robert Hinsley

"P van Rijckevorsel" wrote in message
...
"mel turner" schreef
Well, I do get the impression they have more leaves than normal.
[Perhaps twice as many?]

***
If they have twice as many leaves as normal, maybe it is not that the
leaves
have an unusual position, but that the leaves have their normal postion,
but
twice in each position?

I confess that I'm not quite sure what "twice in each position" means.
There are two leaves at each node of the stem, but they are on
opposite sides of the stem.

It may be that these opposite-leaved plants form approximately the
same number of nodes as their alternate-leaved brethren, which
would of course give them twice as many leaves.

I was just told that there is an already published, known mutation
of corn that causes this morphology. I'll pass on the reference
when I get it.

The thing that struck me as most interesting about these plants is
that this isn't a case of them showing various irregular phyllotaxies.
They are either just as regularly opposite-decussate as any mint plant,
or completely normal and alternate/distichous.

I've also seen the reverse change in some other plant species that are
normally opposite-decussate: some tropical Acanthaceae shrubs in which
individual branches would grow out with what appeared to be a
perfectly regular spiral alternate phyllotaxy.

It's as if the two phyllotaxies aren't all that far apart in terms of
developmental controls.

There of course has to be more to it, or there wouldn't be so many
major taxonomic groups that are all one or all the other. There'd
likely be many more species in which phylltaxy is variable and
irregular on the same plant [Broussonetia papyrifera comes to mind as
being very plastic from opposite to alternate, and I've seen many
Aristotelia shoots go from whorls of 3 or 4 down to opposite and
finally to alternate leaves].

cheers

Stewart Robert Hinsley wrote:
In message , mel turner
writes


Does anyone know if this or similar oddities have been reported before?


Before I chime in, are you interested in aberrations in corn, in
Poaceae, or in general?

I've always been fascinated by Feijoa sellowiana (Myrtaceae), which
commonly has alternate, opposite, whorled (3s) and very occasionally
whorled (4s) on the same shrub/tree. They don't seem to switch during a
growth flush, but when a new flush starts, it can be different from its
parent branch.