I have made the observation that most every plant when it shoots from
its seed
with its first leaves, that these first leaves are rarely (perhaps
never) the same as
what all the other leaves of this plant matures into. Would it not save
the plant
some energy in its early growing if all the leaves were the same from
birth to
maturity?

Anyway, does anyone know if any plant exists wherein its first leaves
are
no different from any other of its leaves?

And the question I am mostly interested in is whether these first leaf
are an
evolutionary vestiges such as human vestiges of gill slits. So are these
first
leaves vestiges of all plants that can be traced back to some ancestral
first
plant. Or, instead of being evolutionary vestiges, are the first leaves
different
from later leaves as in animals the fetus is different from the later
growing
animal.

What I am trying to reconcile in thought is why would a plant invest
energy in
its first leaves of leaves that are very much different from all later
leaves, when
it probably would be better for the plant if all of its leaves during
its entire lifetime were one and the same type of leaf.

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

25 May 2003 21:13:19 -0700 galathaea wrote:
(snipped what I wrote)


While others omg each other to make themselves feel better about being
jerks, I see that some of your question have still been left

Well, my killfile has been greatly effective for the past many years and
you are welcome to copy and use it. I waste none of my time on anything
they write.

http://www.archimedesplutonium.com/M...llfiledom.html


unanswered. One concerns the evolutionary homologies of the
cotyledons, ie. can cotyledon shape be used for phylogenetic
relationships. Unfortunately, the "ontogeny recapitulates phylogeny"

Not exactly sure of what that means, or is trying to convey.

I brought in the subject of animals and vestigial evolutionary form
such as the example of gill slits in humans because it appears that
most first leaves of plants look about the same and are very different
from the later mature leaves of those plants.

So one of my questions was whether these first leaves have some
better energy capture of photosynthesis that later mature leaves lack
in quality of photosynthesis capture. Sort of like the idea that a beginner
child of bicycle uses trainer wheels before going solo.

So are these cotyledon first leaves superior to later leaves? Or would
any and all plants be better off if there first leaves were noncotyledon and
were exactly like all the other later mature leaves? If so would suggest
that cotyledon leaves are evolutionary vestiges just as gill slits in
humans are evolutionary vestiges and although they act as the first
photosynthesis of the plant, they are inferior to the photosynthesis
if these first leaves were not cotyledon but rather instead what the
future mature leaves are.

I doubt any scientist has researched whether a cotyledon first leave
is any superior to later leaves. My guess at this time is that they are
inferior in photosynthesis because they are evolutionary remnants
of the gene coding just like gill slits are remnants of nonfunction.

I would guess if there were a means of testing whether a later leaf is
superior in photosynthesis to a cotyledon leaf that such would be the
case. That is a guess. A guessed based on the idea that animals have
remnants that the gene code cannot seem to get rid of and that the
cotyledon first leaves were the aeons ago leaves like gill slits in humans.

Can you think of a means of testing whether a cotyledon leaf is superior
or inferior in photosynthesis to a later mature leaf? I cannot not at this
moment but I am unfamilar with the literature and methods of botany
to do such a test. Perhaps someone has already found a means of doing
that test.

I have a baby pear true at this very moment coming from seed. It had
a cotyledon first leaves and now it has 2 new leaves of what a pear
leaf really is. So I wonder if a means of testing the photosynthesis
of the cotyledon leaf of pear and then the photosynthesis ability of the
next 2 leaves of that pear is.


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

Yes, my pinenut trees seem to have the same first leaves as later mature
leaves of that pine. But I wonder if any pine or spruce or evergreen has
a cotyledon that looks more like a pear cotyledon than mature pine
leaves. I wonder if we trace all cotyledon leaves of all plants whether that
track leads to the evolutionary history of the past to common ancestors.

Perhaps the gene coding of all plants of the genetic region that does the
cotyledon maybe a marker of the history of all plant species, that we
can tell which species is ancestral to another.


cotyledon often must be structured to particular environments.

Well if that is the case then it sinks the idea that cotyledon is an
evolutionary remnant. Perhaps a fractional or percentage adaption
because most cotyledons are fairly similar. So that environment has
not played much of a role.


However, the cotyledon's role does have a fairly large evolutionary
history in the vascular plants. It was a necessary adaptation to

You know how blood is often compared between species to find out
if one is ancestral to the other. Perhaps cotyledon variations is a marker
in plants to tell if one is ancestral to another.


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

Yes, but that is the important question for me to find out. I want to know
if cotyledon leaves are superior in anyway to later leaves. I would guess
they are inferior because they are evolutionary vestiges like gill slits in
humans that the gene code could not get rid of totally. I would guess that
if plants could have a choice of their first leaves being cotyledon or being
what later mature leaves are that all plants would forego the cotyledon
stage and have all of its leaves, the very first ones all be what the later
mature leaves look like. This guess is based on the presumption that later
leaves of a plant species are its most efficient photosynthethic leaves. And
that the first leaves of cotyledon are like a dumpsite of ancient genetics
of that plant, just as human embryos get rid of its gill slit during the embryo
stage.



2) separates two major evolutionary forms of the vascular plants, the
monocots and the dicots.

I bet if all plants had their choice, they would choice having all their leaves
from their first to their last as all the same and that the cotyledon stage of
a plant is the getting rid of ancient genetics that are there. I would need some
reliable experimental method to test whether cotyledon leaves are superior or
inferior to later leaves. Such a method probably does not exist yet.

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

You must have missed my reply. The first leaves on a flowering plant are not
true leaves, and they are not evolutionary vestiges of anything. They are
called cotyledons, or seed leaves. They are the endosperm that was inside the
seed. They contain starch and/or sugar, and are there to feed the baby plant
until it has enough roots & leaves to feed itself. If you want an analogy from
the animal kingdom, it is the equivalent of the yolk sac on a baby fish.
Go get yourself some dried lima beans. Put them in a jar next to the glass,
backed up by some wet paper towels. Leave them in a well-lit spot for a week or
so & watch what happens.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)

In article ,
Iris Cohen wrote:
You must have missed my reply. The first leaves on a flowering plant are not
true leaves, and they are not evolutionary vestiges of anything. They are
called cotyledons, or seed leaves. They are the endosperm that was inside the
seed. They contain starch and/or sugar, and are there to feed the baby plant
until it has enough roots & leaves to feed itself. If you want an analogy from
the animal kingdom, it is the equivalent of the yolk sac on a baby fish.
Go get yourself some dried lima beans. Put them in a jar next to the glass,
backed up by some wet paper towels. Leave them in a well-lit spot for a week or
so & watch what happens.

He's probably killfiled you for lack of belief in his Atom Totality
religion.

What he should really do is plant some Scarlet Runner beans (Phaseolus
coccineus) next to some common beans (P.vulgaris). The former have
hypogeal cotyledons which don't spread out into "seed leaves". However
both have first true leaves with only one rather than three leaflets.
No doubt this would stimulate ab initio theories about how much more
advanced the former is over the latter, evolutionarily, since the
'seed leaves' are more like 'normal' leaves!

Of course, if he were actually observing rather than pontificating, he
might have noticed a few things about onion and corn seedlings, and if
he would exert himself to open a biology textbook he might learn a bit
about why his pine seedlings look different from his angiosperm
seedlings.

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

I am not sure if there is something similar that goes on in humans with their
baby teeth. Whether that is similar to first leaves of plants. It is said that we
experience baby teeth that fall out before we get real teeth. That maybe just
a myth though.

26 May 2003 22:22:38 -0700 galathaea wrote:
(mine snipped)


Most definitely. We always start grasping and fine tune only later.


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.

What I had tried to convey in my first post was the variability of
forms in the cotyledon. This is strong evidence to point to the fact
that they have been an active part of evolution and are not mere
vestiges. They have a purpose separate from those of the mature
leaves of the plant: although they too participate somewhat in
photosynthesis, they are in reality a part of the seed mass and store
starch and other materials to assist in getting the plant growth
started. Making comparisons between cotyledons and mature leaves
would not be beneficial; they are separate organs with separate jobs.

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.

The reason's cotyledons may not appear in certain plants is because
other seed mass may be sufficient for those plants in the environments
in which they have adapted. Other plants rely heavily on the
cotyledons for their immediate readiness to participate in assisting
the plant's early growth, and photosynthesis, transpiration, and other
tasks normally assigned to leaves may be done by the cotyledons after
first emergence from the soil.

So, basically, what I am trying to show is that the cotyledons should
be seen more as separate organs than as early developmental forms.
They have evolved quite alot and take many forms, and I do not believe
it would be proper either genetically or by form to characterize them
as evolutionary vestiges.

But I do enjoy the question. It is certainly a valid line of
reasoning, and fortunately there is alot known about these fascinating
little cotyledons to provide a fairly good answer. Unfortunately, I
think the answer is most likely negative...

Thanks for answering the question with clarity.

Which leads me to a different line of questioning-- as always in science,
it never ends but leads into new routes and viaducts.

My pinenuts and potatoes do not seem to have cotyledons. So I am guessing
that only plants whose seed is insufficient in energy (ie mass) must have
some cotyledon structure in order for the plant to have enough energy to
reach the noncotyledon-Leaf stage. A pinenut has sufficient energy reserves
that its first leaves are identical to all later leaves and same goes for the
potato. May have that wrong but if correct would suggest that Size of seed
as per mass is directly related to whether a cotyledon must exist or not. The
tomato seed is puny in size and so must have a large cotyledon.

Question for Galathaea if not bored: Has there been a research done on the
size of seed (mass) correlated to whether the plant has or has not a cotyledon
and whether at a particular mass all plants of a greater mass have no cotyledon
(potato, pinenut etc). My pear tree had a cotyledon and its seed is small same
with strawberry seeds but a coconut or nut trees may not have cotyledon?
Is there any correlation between size of seed per mass and whether it has
a cotyledon or not?

P.S. in my earlier post I was asking whether some method exists that tells
us how much photosynthesis is going on per square area of a cotyledon leaf
compared to a mature leaf. In light of the new understanding above that a
cotyledon is a different "organ" so to speak, perhaps we can use cotyledons
as a gauge.

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

moments ago I wrote:



P.S. in my earlier post I was asking whether some method exists that tells
us how much photosynthesis is going on per square area of a cotyledon leaf
compared to a mature leaf. In light of the new understanding above that a
cotyledon is a different "organ" so to speak, perhaps we can use cotyledons
as a gauge.

By gauge I mean that if there exists a math relationship of size by mass to
existence of a cotyledon then also the size of the cotyledon should also be
correlated to size of seed. A strawberry seed is so tiny compared to a pear
seed that the cotyledon of a strawberry should be *relatively* larger than the
pear cotyledon per size.

And so the mass of seed and the size of cotyledon (per mass also) may indicate
how much photosynthesis is taking place between a mature leaf compared to
a cotyledon leaf.

When it all comes down to the essential parts, it is photons of light and
area of photosynthesis and of course mass of the plant structure.

(1) photons
(2) unit of area
(3) mass of plant structure

Has any scientist worked out those 3 parameters on cotyledon?

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

Iris Cohen schreef
They are called cotyledons, or seed leaves. They are the endosperm that
was inside the seed.

+ + +
Although I hate to spoil a good religious argument I feel dutybound to point
out that cotyledons are part of the embryo, and have nothing to do with
endosperm. Reserves can be in both the cotyledons and endosperm: this is
correlated with the systematic position of the taxon in question.
PvR

28 May 2003 12:17:41 -0700 galathaea wrote:



Unfortunately, most of the information on cotyledons I have comes from
textbooks and not research papers (and the textbooks are notoriously
poorly bibliographed). From what I have read, though, there will be
more constraints on the system than due to the functionality you have
mentioned because the cotyledons are also sources of starch storage in
the early plant development. To a great extent this will come from
the seed mass, and so there does seem to be an opposite relationship
at work here too: that cotyledon size will likely not grow that large
for small seeds. If you couple this with the statements found in a
couple of books that photosynthesis occurs less in the cotyledons
(probably an over generalization, but the observation is probably one
of measuring fraction of chlorophylls which one can extract from a
cotyledon versus mature plant leaves), then you probably have a
limiting factor to size. In fact, it would appear that overgrowth may
be counteractive, and that the size factors due to photosynthetic
capabilities and plant food storage might be more applicable to the
true leaves. And of course, there is the crucial factor of
transpiration and the environmental niche which the plant resides in,
where the size differences can be extraordinary (desert plants versus
tropical plants for the extremes).

But I do think there are likely important relationships here, and if a
literature search turns up empty, doing the biometric studies would
certainly be a proper exploration for you. I don't think any of the
relationships will be linear (which in my book is a plus!). Good luck
in your quests for knowledge!

Well thanks. I see that you post to sci.logic and sci.math also. Keep up the
good work of furthering science with discussion. I may return to cotyledon
thoughts.

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

From: Archimedes Plutonium

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.

The cotyledons of a seed are often adapted for storage purposes, and not as
efficient photosynthesis organs. There are some cases where the cotyledons are
good at photosynthesis, such as _Ipomoea_, and some other cases where the
cotyledons photosynthesize and the leaves do not (to any appreciable extent)
such as _Cuscuta_. In general, cotyledons confer some advantage to the plant
by supplying stored nutrients as well as often giving a little bit of
photosynthetic product as well.

Sean



--
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Last updated 08-04-02 with 15 pictures of the Aztec Ruins.
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Sean Houtman schreef
The cotyledons of a seed are often adapted for storage purposes, and not
as efficient photosynthesis organs. There are some cases where the
cotyledons
are good at photosynthesis, such as _Ipomoea_, and some other cases where
the
cotyledons photosynthesize and the leaves do not (to any appreciable
extent) such as _Cuscuta_. In general, cotyledons confer some advantage to
the
plant by supplying stored nutrients as well as often giving a little bit of
photosynthetic product as well.

Sean

+ + +
A very narrow view, disregarding all plants with hypogeal germination. To
say nothing of [...]
PvR