Posted November 2011


In Celebration of Psalm Nineteen:
God's handiwork in Creation

Chapter 10

The Creation of Early Plant Life*

NOTE:  See the page on plant body plans for a systematic summary of the plant phyla with early fossil examples. See the page on Body Algorithms for a discussion of the logic that is the basis of plant and animal body plans.

IntroductionPlants first appear in the fossil record as part of the great migration of life from the oceans to land, about 100 My after the first animals appeared. Prior to the appearance of plants, animals fed on the wastes of former life, and on bacteria, algae and one another. After plants and animals had established themselves on land, plants became the main (ultimate) source of food for land animals from grubs and insects to land animals and humans.

Plants naturally are associated with land because they are
air-breathing, and all except liverworts have stomata which help to regulate the passage of gases (water vapor, oxygen and carbon dioxide).01 All plants propagate sexually (at some stage in their life cycle) with embryonic spores or seeds02.

The delay in the appearance of plants, relative to the more complex animals (which appeared in the Cambrian, about 530 Ma), is because their arrival had to await the build-up of the ozone layer, which filters out the hard cosmic and solar radiation. This ozone layer gradually built up over the billion years after oxygen had reached a stable level (20-25%) in the atmosphere. The layer became an adequate filter during the late Silurian and the Devonian eras, about 450-400 Ma. Before this, the "greening of the land" was accomplished by algae and bacteria, which could thrive in spite of the lethal effects of cosmic rays because of their high reproduction rate.

The arrival of the main kinds of plants was relatively more drawn-out than was the case for animals (cf. Figure 1). The first plants appear in the late Silurian. The Devonian sees a great expansion of the simpler vascular plants which continues into the Carboniferous and Permian. In the Carboniferous, seeds and the conifers appear -- the gymnosperms, proper woody plants with an expansion of the secondary xylem. With the invention of seeds, the plants can for the first time move away from wet lowlands and begin to populate the higher and dryer regions of land. These seed plants proliferate through the Carboniferous, producing the great coal deposits. In the Permian, the crowning invention -- the flowering plant, the angiosperm -- appears, with seeds surrounded by nutrients (the ovary) to begin a new life.

Part of the fascination in the Creation Narrative for plants, is to contemplate just why this counter-intuitive extended creation of plants took place: after all, the spectrum of body plans for animals seems to be so much more complex than one finds with plants, and yet the full spectrum appeared earlier and in much more compressed time. Part of the answer seems to be that the development of plants had to take place as environmental conditions changed to support new innovations, and also because in many cases plants (in particular the angiosperms) developed in parallel with animals, particularly with flying insects and birds, in a symbiotic relationship.

Plant History
Figure 1
Geological Plant History03 
The Marcellus Shale. The Marcellus Shale is an interesting marker to start the discussion of the creation narrative for plants. There are few fossil remains in this formation, and it is likely that the main source of organic material is from bacteria and algae, which by the Margulis classification are Protists, not plants. However, Dana reports that spores are abundant04.

The shale (see the box) forms a thick black Permian layer just under the  fossil plant-bearing formations of northeast U.S.  Similar black shale formations occur worldwide, dating to roughly the same period. These black shales formed from algae during the Devonian Era, and were deposited in the oxygen-free bottoms of vast inland, mostly freshwater, lakes that covered the emerging North American continent.

The shale is relatively impermeable, so liquid and gaseous body remains were trapped, forming oil on the shallower western regions and gas on the deeper eastern regions, under heat and pressure. Recently these shales have become the source of "unconventional" oil and gas, as a result of hydraulic fracking which breaks up the shale and makes the trapped oil and gas available for extraction. The source is "unconventional" because the oils and gases are the products of algae, rather than land plants and animals.

The Marcellus Shale

Wiki: "Stratigraphically, the Marcellus is the lowest unit of the Devonian age Hamilton Group (400 Ma), [coincident with the earliest evidence of plant fossils -- e.g. the Rhynie cherts -- and shortly after the ozone layer was an adequate filter against cosmic rays so it could allow migration of plants and animals to land.--dcb]. The black shale was deposited in relatively deep water devoid of oxygen. ... To the west the formation may produce liquid petroleum; further east heating during deeper burial more than 240 million years ago cracked this oil into gas. ... The Marcellus Shale was formed from the very first deposits in a relatively deep, sediment- and oxygen-starved (anoxic), trough."

Marcellus Shale
Figure 2
Marcellus Shale
Vertical Cross-section Ohio to Pennsylvania

The carbonaceous black shales of the Marcellus Formation are at the base of the sedimentary rocks that contain organic remains over a broad region from New York to Virginia and the Mississippi to the Delaware River.

The First True Plants. The first fossil evidence for (multicellular) plants is the appearance of spores, around 470 My, during the Ordovician Era (488-443 Ma). Spores typically are airborne, and many of these first spores are trilete (indicating sexual reproduction and derived from a 4-way division of the mother spore into tetrads -- see Figure 3, and the box on Pollen, Spores and Seeds). They are the first indication of land -- or at least air-breathing -- plants. These early spores preceed the first actual plant fossils by over 50 My.

Devonian-SporeTetrad.gif Devonian-Spores.jpg
Figure 3a
Spore Tetrads
Rhynie Chert, ca. 400 Ma
Lower Devonian
Figure 3b
Archegonium ejecting sperm cells
Rhynie Chert
Lower Devonian

Because the early plant fossils were soft-bodied, it is not surprising that they didn't show up in the fossil record until much later than the hard-cased spores.
The earliest actual plant fossil is Cooksonia, a leafless vascular plant dated to about 416 Ma, at the boundary between the Silurian (443-416 Ma) and Devonian (416-359 Ma) eras (Figure 4).

Cooksonia-Wiki Cooksonia pertoni
Figure 4a
Cooksonia - Earliest Vascular Plant Fossil
Upper-Silurian, ca. 416 Ma
showing sporangia fruits.
Figure 4b
Cooksonia pertoni.
Upper-Silurian, ca. 416 Ma
Shropshire, England. Height 1 inch.

The Rhynie Chert (Early Devonian). By an act of providence, a Lilliputian forest of early small soft-bodied plants has been preserved
in-situ as full, undistorted 3-dimensional fossils, and dating to about 410-390 Ma, at the beginning of the Devonian Era (416-359 Ma) (Figure 5a). These are generally classified in the same (extinct) phylum as Cooksonia (phylum Rhyniophyta), and are vascular plants, with no leaves, but with sporangia and proper stomata, indicating aerobic photosynthesis.

Figure 5a
Rhynie Chert
Rhynia gwynne-vaughanii
Figure 5b
Algaophyton major
Rhynie Chert
Note: See also Figure 3.

The preservation in the Rhynie Chert is so detailed and complete that it is as if the plants had been photographed in three-dimensional form, in an instant of time, including "live" action shots such as the ejection of sperm cells from sporangia (Figure 4b). The preservation extends to microscopic details, and includes all growth stages of these vascular plants, and so are ideal for a deep scientific understanding of these first plants. They are vascular plants that grow from rhizomes (underground stems typical of club mosses, horsetails and ferns -- not proper roots). They do not have proper leaves, but are photosynthetic and do have stomata along the stems (which can be examined in microscopic detail).

The Rhynie chert was discovered by William Mackie while mapping the western margin of the Rhynie basin near Aberdeen, Scotland, in 1910–1913.

Devonian Flora -- The Devonian Era (416-359 Ma) was the start of a rapid expansion of land plants. During this period most of the features of plants -- except flowers -- appeared: rhizomes, roots, vascula (xylem and phloem), stomata, leaves, bark, secondary (supportive) wood, and seeds. The Devonian era ended with the Devonian Extinction which appeared to affect only marine animals, particularly corals.

The plants of the Rhynie chert were small in size, but they were followed in the late Devonian by forests of surprisingly tall trees. Many of the plants characteristic of the Devonian also appear throughout the Carboniferous. "A large part of the difference between the Devonian and Carboniferous floras is probably related to different geographical conditions. The wide swampy flats of the Coal period do not seem to have existed in the Devonian era. The land was probably less extensive and more of an upland character." [Dawson,
Acadian Geology, p. 533]

Figure 6 shows a typical forest scene from the Devonian Era. The plants of this era have relatively little woody matter, but still attain quite remarkably large size -- see for example the remarks on the Sigillaria (Figure 7), an ancient plant of the Lycophyte phyum (Pl-4), today represented by club mosses and lycopods, which are found on forest floors, grow from rhizomes (typical of phyla up to the ferns (Pl-7)) and reach a height of  a few inches. Similarly the Calamites are related to the modern Horsetails (Pl-6), also a small plant today. In addition to these there were a number of fern-like plants.

Marcellus Shale
Figure 6
A Devonian Scene
Showing A: Calamites; B: Psilophyton; C: Lepidodendron;
D:Lepidodendron; E: Cordaites; F: Sigillaria; G: Megalopteris;
H: Dadoxylon (a conifer); I: Asterophyllites; J: Cordaites;
K: Platyphyllum (Archaeopteris); L: Dragonflies (shown in error:
Carboniferous, not Devonian)05.
Dawson, Plants (1888), p. 49

Marcellus Shale
"A lumber-man would probably regard it as a tree nearly all bark, with only a slender core of wood in the middle ; and, botanically, he would be very near the truth. The outer rind or bark of the tree was very hard. Within this was a very thick inner bark, partly composed of a soft corky cellular tissue, and partly of long tough fibrous cells like those of the bark of the cedar. This occupied the greater part of the stem even in old trees four or five feet in diameter. Within this we would find a comparatively small cylinder of wood, not unlike pine in appearance, and even in its microscopic structure ; and in the centre a large pith, often divided, by the tension caused in the growth of the stem, into a series of horizontal tables or partitions. Such a stem would have been of little use for timber, and of comparatively small strength. Still the central axis of wood gave it rigidity, the surrounding fibres, like cordage, gave the axis support, and the outer shell of hard bark must have contributed very materially to the strength of the whole."
Dawson,     Acadian Geology, p. 431
Figure 7
Sigillaria (Upper Devonian and Carboniferous Eras)
Related to Club-Mosses and quill-worts (Pl-4)
Height up to 100 ft.
Trunk diameter up to 5 ft.
Dawson, Plants (1888), p. 112

Most of the plants in the Devonian Era propagated with spores (think of ferns today). Spore germination required a moist environment. The development of true seeds was needed to complete the transition to land, unrestricted by the need for a moist environment. True seeds first appeared in the late Devonian era. They were fern-like and seed bearing. Originally classified as cycads (which are modern seed-bearing) the name settled down to "seed ferns" (the literal translation of pteridosperms). Today, they are considered an extinct intermediate between ferns and cycads, but not directly related to modern ferns06.  "The most noticeable feature of these species is that the trunks contained very little woody tissue. Unlike all other tree-like plants the growth in girth, and therefore the stability of the entire plant, was generated by the bark.... Microscopic investigations have indicated that as much as 70% of our coal measures may have been created from these tree-like lycophytes [club-mosses].08"

Over the course of the Devonian Era, the root structures changed (Figure 8). Most of the rhizomes and roots were shallow. True roots as found in modern plants did not appear until later. The closest to true roots (stigmaria) branched like trees rather than like modern roots.

Figure 8
Devonian Plant Roots

left to right -- rhizomes: rhyniophytes, trimerophytes, herbal lycopods;
roots: tree lycopods; Tetraxylopteris & Archaeopteris progymnosperms;
gymnosperms  Elkinsia & Moresnitia;
rhizomes: zygopterid (extinct true fern) Rhacophyton09.
Gensel & Edwards, Plants Invade the Land, fig. 12.3 (2001)0

The Carboniferous Flora -- Gymnosperms. In the Carboniferous Era (359-299 Ma) the plants of the Devonian continued to flourish. Insects (originating in the Devonian) flourish in this era. All insects have three body parts: head, three-segment thorax and eleven segment abdomen10. Insects were the first flying animals. Fully-winged species appeared suddenly in the Carboniferous (380 Ma) and disappeared even more suddenly in the Permian (250 Ma)11. A startling example is the very large dragonfly-like insects with gossamer wings (Figure 9, cp.  Figure 6 (L)). These are the largest insects that ever lived. See the Box for a summary of the plant types found in the Carboniferous era.

Figure 9
Carbonaceous meganeurid dragonfly
(sub-)class Paleoptera
reconstructed (falsified) fossil
body length 1 ft. wingspan 2.5 ft.
Inset shows actual fossil -- most fossils are fragmentary.

Figure 10
Plant Diversity Tree

Univ. New Mexico

Figure 11 shows Carboniferous foilage and Figure 12 shows a typical Carboniferous scene, which is similar to a Devonian forest scene (Figure 6).

Figure 11
Carboniferous Foliage
Showing: A: Alethopteris (fern); B: Sphenophyllum; C: Lepidodendron (quillwort);
D: Asterophyllites (horsetail); E: Cordaites (gymnosperm); F: Neuropteris (fern);
G: Odontopteris (fern).

  Dawson, Plants (1888) p. 111

Figure 12
A Carboniferous Scene
Showing: A: Odontopteris (fern);  B: Lepidodendron (quillwort);
C: Cordaites (gymnosperm: seeds up to 1 cm. are common);
D: Pecopteris (seed fern); E: Calamites (horse-tail);
F: Sigillaria (club moss); G: Stigmaria (roots)

The main innovations in the Carboniferous era are the first conifers -- pines -- which are relatively rare fossils. The conifers appear to be upland plants which are washed down into the swampy coal formations

Dawson Acadian Geology notes: p421 Flora of Coal Formation

The Permian Flora -- Angiosperms.


The sudden appearance of angiosperms: Darwin called the origin of angiosperms an "abominable mystery". Angiosperms appear rather suddenly in the fossil record, with no obvious ancestors for a period of about 80 to 90 million years prior to their appearance. Not even fossil leaves or pollen are known from this earlier time.  D.I. Axelrod has suggested that we do not find early angiosperm fossils because the earliest angiosperms lived in dry, upland habitats where the were unlikely to be preserved as fossils. Though this idea has long been accepted, it has not been well investigated and so remains to be tested.

"Daniel Isaac Axelrod (1910-1998) suggested that we do not find early angiosperm fossils because the earliest angiosperms lived in dry, upland habitats where they were unlikely to be preserved as fossils. Though this idea has long been accepted, it has not been well investigated and so remains to be tested."  -- UCMP Berkeley 



The Stresses of Colonizing Land -- "Organisms in water do not face many of the challenges that terrestrial creatures do. Water supports the organism, the moist surface of the creature is a superb surface for gas exchange, etc. For organisms to exist on land, a variety of challenges must be met.

   1. Drying out. Once removed from water and exposed to air, organisms must deal with the need to conserve water. A number of approaches have developed, such as the development of waterproof skin (in animals), living in very moist environments (amphibians, bryophytes), and production of a waterproof surface (the cuticle in plants, cork layers and bark in woody trees).
   2. Gas exchange. Organisms that live in water are often able to exchange carbon dioxide and oxygen gases through their surfaces. These exchange surfaces are moist, thin layers across which diffusion can occur. Organismal response to the challenge of drying out tends to make these surfaces thicker, waterproof, and to retard gas exchange. Consequently, another method of gas exchange must be modified or developed. Many fish already had gills and swim bladders, so when some of them began moving between ponds, the swim bladder (a gas retention structure helping buoyancy in the fish) began to act as a gas exchange surface, ultimately evolving into the terrestrial lung. Many arthropods had gills or other internal respiratory surfaces that were modified to facilitate gas exchange on land. Plants are thought to share common ancestry with algae. The plant solution to gas exchange is a new structure, the guard cells that flank openings (stomata) in the above ground parts of the plant. By opening these guard cells the plant is able to allow gas exchange by diffusion through the open stomata.
   3. Support. Organisms living in water are supported by the dense liquid they live in. Once on land, the organisms had to deal with the less dense air, which could not support their weight. Adaptations to this include animal skeletons and specialized plant cells/tissues that support the plant.
   4. Conduction. Single celled organisms only have tyo move materials in, out, and within their cells. A multicellular creature must do this at each cell in the body, plus move material in, out, and within the organism. Adaptations to this include the circulatory systems of animals, and the specialized conducting tissues xylem and phloem in plants. Some multicellular algae and bryophytes also have specialized conducting cells.
   5. Reproduction. Organisms in water can release their gametes into the water, where the gametes will swim by flagella until they ecounter each other and fertilization happens. On land, such a scenario is not possible. Land animals have had to develop specialized reproductive systems involving fertilization when they return to water (amphibians), or internal fertilization and an amniotic egg (reptiles, birds, and mammals). Insects developed similar mechanisms. Plants have also had to deal with this, either by living in moist environments like the ferns and bryophytes do, or by developing specialized delivery systems like pollen tubes to get the sperm cells to the egg."

Plant Species in the Devonian and Carboniferous Strata
"After the surprisingly fast radiation of land plants in the Devonian, the Carboniferous is characterised rather by a further diversification of the already existing groups, than by the appearance of new groups."07.0

Rhyniophyta (extinct phylum)
Early Devonian (410 Ma).
Rhynie Chert
Sporangia, Rhyzomes,
Leafless (Stomata in stems)
Lycopods (Lycophytes, Pl-4)
Club Mosses, Quillworts07.1 Early Devonian (410 Ma to Present)
Oldest vascular plant still living today.
Produced up to 80% of coal from Carbonaceous07.1.
Sporangia, Needle leaves, Rhyzomes. homo- & heterosporous species.

Middle Silurian (Australia)

Middle Devonian

Trees to 120 ft.
minimal woody fiber,

Stigmaria (roots)
Sigillaria (leaves, branches)

spikemosses. [possibly] "longest living genus of higher land plants."07.1
The Carboniferous lycophytes of the order Lepidodendrales, which are cousins (but not ancestors) of the tiny club-moss of today, were huge trees with trunks 30 meters high and up to 1.5 meters in diameter. These included Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria. The roots of several of these forms are known as Stigmaria.

Equisetales (Sphenopsids) (Sphenophytes, Pl-6)
Horsetails07.2   Late Devonian (small size); large trees in Carboniferous. Articulated axes and leaves standing in whorls.
Cylindrical with pith-filled cavity. Thin wood, thick bark.

Calamites Giant Horsetail
Trees to 100 ft.
Extinct in lower Permean
Articulated stem (bamboo-like)
Asterophyllites = leaf whorls
Annularia = leaf whorls

wedge-shaped leaves
------  cladoxylopsid trees Wattieza 
Mid-Devonian (385 Ma)
Earliest known trees (35 ft.), resemble tree-ferns07.3 
Spores, Frond crown rather than leaves
True wood, true roots
Progymnosperm (Cycads, Pl-8?)
Cycads, Conifers07.6
Late-Devonian. Extinct in early Carboniferous. Trees (100 ft.). Spores, Wood (Callixylon) similar to conifers. True Leaves? First tree with extensive root system.
Vascular cambium, xylem, phloem

Archaeopteris "the first modern tree" annular rings, webbed leaves.

Walchia Late Carboniferous (ca. 310 Ma)

Filicinophytes (Pl-7)
True Ferns
Dominant plant in late Carboniferous after extinction of most lycopods. pteridophylls = informal categories for fern(-like) foilage .  Difficult to distinguish true fern foliage from seed fern foliage.07.4





Late Carboniferous.
Oldest extant (true) fern group.

Pteridosperms (Cycads, Pl-8?) Seed-ferns (Lyginopterids) Late-Devonian. Loose collection of plants of uncertain relationship. Major plant mass through Carboniferous. Extinct?
First true seed plants. Seeds, ovules (where seed develops). Micropyle (pollen opening)07.5.

end devonian

more like conifers

Carboniferous  (small) tree fern

Late Carboniferous. Closest relative to conifers.


Note: For a highly readable account of the Flora of the Coal Formation, see the books by Dawson07.7.

Stomata and Engineering Perfection
quotes from (Evolutionary History of Plants)
developed in parallel with a waxy (water-tight) cuticle.


"The fossil record has little to say about the evolution of stomata... It is clear, however, that the evolution of stomata must have happened at the same time as the waxy cuticle was evolving - these two traits together constituted a major advantage for primitive terrestrial plants." -- Wiki

Cellulose, Lignin and Wood
quotes from (Evolutionary History of Plants)

To understand wood, we must know a little of vascular behaviour. The stele of plants undergoing "secondary growth" is surrounded by the vascular cambium, a ring of cells which produces more xylem (on the inside) and phloem (on the outside). Since xylem cells comprise dead, lignified tissue, subsequent rings of xylem are added to those already present, forming wood.

Archaeopteris, a precursor to gymnosperms which evolved from the trimerophytes,[58] reached 30 m in height. These progymnosperms were the first plants to develop true wood,

Lepidodendrales differ from modern trees in exhibiting determinate growth: after building up a reserve of nutrients at a low height, the plants would "bolt" to a genetically determined height, branch at that level, spread their spores and die

       From U. Manchester grant description: "Cellulose is the world’s most abundant biopolymer. In plants it is synthesised by a very large membrane bound complex that acts as a molecular nanomachine simultaneously making many individual chains of cellulose that bind to together to form a cellulose microfibrils. These microfibrils are very strong and among the most insoluble biomolecules, despite these many remarkable properties, an understanding of how cells are able to synthesis these microfibrils remains elusive."
    see References: CelluloseBiosynthesis-Diotallevi.pdf  CelluloseBiosynthesis-2010.pptx

wood is cellulose (for tensile strength) + lignin (for compression strength). Invented at beginning of devonian. (fossils 2011). What "coordinates" the construction of wood?

Hans Kerp, A History of the Palaeozoic Forests  :
First plants:"a very resistant impenetrable outer layer, which is named the cuticle"  rhizomes, stomata.
Mid Devonian: "the development of true roots ... and complex vascular systems" Secondary wood. Evolution of the leaf: small needle-shaped leaves; in other groups of plants branched lateral axis systems,  the forerunners of fern-like fronds.
Late Devonian: the earliest tree-like plants appeared and forest-like stands. Archaeopteris with frond-like axis systems with fan-shaped leaflets. The wood is anatomically remarkably similar to that of the primitive conifers. Heterosporous (large and small spore differentiation).
End Devonian: seed-ferns (pteridosperms) These plants had fern-like fronds and did not reproduce with spores but with real seeds and pollen grains. Gymnosperms. Most of the presently still existing groups (lycophytes, sphenopsids, ferns and gymnosperms) had appeareded by the end of the Devonian. The earliest trees and forests are Late Devonian in age.
Carboniferous: "After the surprisingly fast radiation of land plants in the Devonian, the Carboniferous is characterised rather by a further diversification of the already existing groups, than by the appearance of new groups."
Permian: considerable changes in the composition of the flora can be seen. The hitherto widespread tree-like lycophytes largely became extinct; only very few forms locally persist. In the Early Permian of Europe and North America only a single tree-like lycopsid is known: Sigillaria brardii. This plant was very tolerant with regard to its habitat, although it always grew in humid environments. The causes have never been explained in a satisfactory way. Several authors relate the almost complete extinction of arborescent lycopods to climatic changes. Northwest and central Europe drifted in northward direction. By the end of the Permian it had reached a position of approx. 30° N [From an equatorial position during the Carboniferous]. This means that the continental plates wandered through the climatic zones. The floras of the Upper Permian generally have a very low diversity and are dominated by conifers. Many of these forms have thick and fleshy leaves, usually with thick cuticles covered by many hairs. This suggests a warm and dry climate. An arid climate is also indicated by the presence of thick evaporite deposits.
Permian Extinction. According to recent estimations, about 95% of all plant and animal species and 50% of all genera became extinct at the end of the Permian (Erwin 1993). This is the largest mass extinction in Earth's history. Although many plant species and genera became extinct, the larger groups of plants mostly persisted. Many genera of conifers which were dominant in the Late Permian disappeared, but were replaced by others and also in the Triassic conifers were often predominant. This is in strong contrast to the fauna; several groups of animals became completely extinct like the trilobites.
Figure 13
Development of Early Land Plants

Figure 14
Chart of First Appearances of Major Plant Groups

The big thing missing is angiosperms.

Xylem and Phloem
quotes from (Evolutionary History of Plants)

The early Devonian landscape was devoid of vegetation taller than waist height. Without the evolution of a robust vascular system, taller heights could not be attained.


programmed cell death required "allowing their innards to be emptied and water to be passed through them"

"defunct tracheids are retained to form a strong, woody stem.

Vessels first evolved during the dry, low CO2 periods of the late Permian, in the horsetails, ferns and Selaginellales independently

quotes from (Evolutionary History of Plants)

why did it take so long for leaves to evolve in the first place?
Leaves certainly evolved more than once

venation: web vs straight.  microphylls, that lack complex venation    megaphylls, that are large and with a complex venation.

Today's megaphyll leaves probably became commonplace some 360mya, about 40my after the simple leafless plants had colonized the land in the early Devonian period.


quotes from (Evolutionary History of Plants)

But how and when did roots evolve in the first place?

sigillaria --

 quotes from (Evolutionary History of Plants)

 quotes from (Evolutionary History of Plants)

The members of the MADS-box family of transcription factors play a very important and evolutionarily conserved role in flower development. According to the ABC Model of flower development, three zones - A,B and C - are generated within the developing flower primordium, by the action of some transcription factors, that are members of the MADS-box family. Among these, the functions of the B and C domain genes have been evolutionarily more conserved than the A domain gene. Many of these genes have arisen through gene duplications of ancestral members of this family. Quite a few of them show redundant functions.

Some MADS-box genes of flowering plants have homeotic functions like the HOX genes of animals

The Creation of Cellulose
"One of the great enigmas in plant biology is the biosynthesis of cellulose."
"Cellulose is the most abundant macromolecule on earth." It is an essential part of algae and all vascular plants, formed from glucose, the major product of  photosynthesis. It crystallizes into rigid rods called microfibrils (CMFs), which have a tensile strength greater than steel.

The trans-membrane cellulose synthase complex (CSC) = Hexagonal rosette = enzyme composed of 36 CSEA proteins that makes cellulose. The rosettes are the exclusive location of cellulose assembly for all land plants. The genes that form this complex are called CESA genes. The plant with the smallest dna, Arabidopsis (mustard), has 10 CESA genes.

Q: if it is made of sugar why is it so hard to metabolize by almost all animals (requires bacterial assistance)? Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides. Anaerobic bacteria like Celluomonas produce cellulase enxzymes to break down cellulose.

Fabiana Diotallevi, : The Physics of Cellulose Biosynthesis (2007)

Insect Wings
"The insect wing is not just a membrane that juts of the insect’s body. It’s a complex of membranes, veins, folds and flexures – looking at it laterally, it is in no way a simple two-dimensional structure. Even more mind-boggling is the wing base, with all sorts of sclerites as muscle attachment sites, plates, vein sources and the notal margin. It is to the wing base that all the power generated by the thoracic muscles goes, so it is also imperative to the way an insect flies."



* Background is a Carboniferous forest from

^n01  Liverworts (Margulis' phylum Pl-2 Hepatophyta) exchange gases through pores which appear to be similar to stomata, but they remain open -- so they cannot control water loss by closing, as proper stomata do. Hence liverworts must live in a wet or moist environment -- although some species have a remarkable ability to revive after complete dessication. See Marchanatia polymorpha and Jungermanniophyta.

^n02  Margulis: p. 413 "Plants are adapted primarily for life on land, although many dwell in water during part of their life history... Many plants grow and reproduce in ways that bypass the two-parent sexual fussion [but] all must have evolved from ancestors that formed embryos by sexual fusion."

^n03 The Wiki article Evolutionary History of Plants gives a useful outline of the development.

^n04 Dana, Manual of Geology (1896) p. 596 "Spore-cases and spores are abundant in the black Marcellus shale of New York and Pennsylvania, and are a prominent source of its bituminous character. They are usually minute black shining spots in the shale."

^n05  The inference that dragonflies were present in the Devonian was based on fossil wing fragments widely noted in geology books of the late 1800s: See for example, Dana Manual of Geology pg. 600, Figures 923, 924, and Dawson, Acadian Geology Figures 181-184, p. 521-2. See Randal F. Miller, History of Geological Investigation of Saint John, New Brunswick: "Along with plants the site yielded reptile/amphibian tracks. Arthropods, particularly insect remains, attracted attention from geologists worldwide. At the time the rocks were considered to be of Devonian age, making the insect assemblage the oldest known in the world... Subsequent work by British paleobotanist Marie Stopes (1914) in a Geological Survey of Canada Memoir proved the Carboniferous age of the rocks."

^n06  See the Wikipedia articles on Pteridosperms and Evolutionary History of plants. "the seed, which is one of the most dramatic innovations during land plant evolution."

^n07.0  Hans Kerp, A History of the Palaeozoic Forests

^n07.1 See table of Lycopods at Paleobotanical Research Group, Münster University,  FOSSIL  AND  EXTANT SPHENOPHYTES, page 6

^n07.2 See table at Paleobotanical Research Group, Münster University,  FOSSIL  AND  EXTANT SPHENOPHYTES, page 7

^n07.3  Oldest Tree had fronds, not leaves. 18 April 2007. Wattieza is World's Oldest Tree. Cosmos Magazine, 19 April 2007.

^n07.4  See table at Paleobotanical Research Group, Münster University, Fossil (True) Ferns, page 8

^n07.5  See table at Paleobotanical Research Group, Münster University,  Seed Ferns, page 9

^n07.6  See table at Paleobotanical Research Group, Münster University,  Conifers, page 10  See also Cycads, page 11.

^n07.7  See "Flora of the Coal Formation" in  Dawson, J. William (Sir), Acadian Geology (3rd. Edition, 1878), p. 421ff; and Dawson, J. William (Sir), The Geological History of Plants (1888), p.110ff.

07.8   ^n07.8  n

07.9   ^n07.9  n

^n08 The flora of the Carboniferous coal forests.

^n09  The late devonian flora were dominated by Archaeopteris (a cycad, "the first modern tree") and Rhacophyton (arguably a true fern). See Devonian Times. The archaeopteris were large tree-like plants, height up to 30 m; and the Rhacophyton were tall shrubs, height 1-1.5 m.

^n10  North Carolina State University, Evolution and Diversity. Chapter 2, pg. 4 of John R. Meyer, General Entomology.

^n11  Ibid. "all [theories of wing evolution] fail to explain how or why such appendages acquired a hinge-joint mechanism, strong thoracic musculature, and the neural complexity necessary for sustained flight. appears that the ability to fly evolved only once in the class Insecta."  See also Insect Flight: Early Fossil Record: "The insect wing is not just a membrane that juts of the insect’s body. It’s a complex of membranes, veins, folds and flexures – looking at it laterally, it is in no way a simple two-dimensional structure. Even more mind-boggling is the wing base, with all sorts of sclerites as muscle attachment sites, plates, vein sources and the notal margin. It is to the wing base that all the power generated by the thoracic muscles goes, so it is also imperative to the way an insect flies."

^n12  Dawson, Acadian Geology, op. cit. p. 423. "Four species of pines have been recognised in the Coal formation of Nova Scotia and New Brunswick. They are known principally as drift trunks imbedded in the sandstones, and these are so abundant as to indicate that extensive pine forests existed, perhaps principally in the uplands, higher than the Coal swamps. The trunks are also frequently so well preserved, owing to the infiltration of carbonate of lime or silica into their cells, that their most minute structures can be observed as readily as in the case of recent wood. They may all be included in the genus Dadoxylon, a name which means simply pinewood."

13   ^n13  n

14   ^n14  n

15   ^n15  n

16   ^n16  n

17   ^n17  n

18   ^n18  n

19   ^n19  n

20   ^n20  n



Dawson, J. William (Sir), Acadian Geology (3rd. Edition, 1878). Sir Dawson was an expert on Acadian (Eastern Canadian) geology
Dawson, J. William (Sir), The Geological History of Plants (1888). This is a remarkably readable early account of fossil plants.

Hans Kerp, A History of the Palaeozoic Forests 

George Langford, Sr.  Fossil Flora and Fauna of the Pennsylvanian Period, Will County, Illinois

North Carolina State University, Evolution and Diversity. Chapter 2 of John R. Meyer, General Entomology.

Steur, Hans, Hans Steur's Paleobotany Pages

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Posted November 2011