[Plant-biology] Corn plants with opposite leaves?

mel turner mturner at snipthis.acpub.duke.edu
Wed Jan 18 13:31:18 EST 2006


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







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