25 May 2003 21:13:19 -0700 galathaea wrote:


unanswered. One concerns the evolutionary homologies of the
cotyledons, ie. can cotyledon shape be used for phylogenetic
relationships. Unfortunately, the "ontogeny recapitulates phylogeny"
pattern found in animals does not apply anywhere near as well in
plants. This is particularly true after the seed is formed, were much
separation of form has alreadt occurred. The cotyledon's shape can be
fairly similar across several species of a genera, but it rarely keeps
this similarity over genera. This is because the duties of the
cotyledon often must be structured to particular environments.
However, the cotyledon's role does have a fairly large evolutionary
history in the vascular plants. It was a necessary adaptation to
support plant growth through to the phase where it can produce enough
food on its own by photosynthesis. In fact, the number of them (1 or
2) separates two major evolutionary forms of the vascular plants, the
monocots and the dicots.

I think I can summarize my initial question better today. Often it takes
several days to make a question better.

Question: Why should any plant have its first two leaves very much different from all other successive
leaves? That is the question that is bothering me. Why
should my baby pear tree have its first two leaves so starkly different from
its future leaves. Do these first leaves confer some superior advantage to the plant
or are they different because of the ancient past of the species, the genetic mess
of the species is brought forth in its first leaves.

I believe it is a question of whether genetic-mess (like gill slits in humans) or
whether these first leaves confer some survival advantage on the seed growing
to maturity.

My guess is that it is "genetic mess of the past". And that if the plant had a choice of having its
first leaves such as a pear tree, that the plant would have
all of its leaves of one type. That the true pear leaf is superior in every way
such as photosynthesis ability than the cotyledon first leaf.

Archimedes Plutonium,
whole entire Universe is just one big atom where dots
of the electron-dot-cloud are galaxies