first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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) |
first leaves of plants-- thought of as evol.vestiges or
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. |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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. |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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 |
first leaves of plants-- thought of as evol.vestiges or
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 |
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