Topic 5: Seedless Vascular Plants (Ch. 29)

BIOL 1030 – TOPIC 5 LECTURE NOTESTOPIC 5: SEEDLESS VASCULAR PLANTS (CH. 29)I. Vascular Plants (overview) – plants with xylem and phloem  7 or 9 living phyla, depending on who you talk to able to dominate most terrestrial habitats because of vascular tissues, waxy cuticle, and stomata conducting tissues (xylem and phloem) called vascular tissues cylindrical or elongated cells that form network throughout plant xylem  xylem of all vascular plants includes tube-shaped cells that carry water and minerals up from roots  When functioning, these cells are dead, with only their walls providing a system of microscopic water pipes  typically at least partially lignified (having lignin, a highly branched polymer that makes cell wall more rigid) phloem  transports carbohydrates, sugars, amino acids and other organic products in solution throughout plant (down and up)  living cells  roots, leavs and shoots  Roots :  Lignified vascular tissue also allowed the evolution of roots. anchor vascular plants and enable them to absorb water and nutrients from the soil.  allow the shoot system to grow taller. Leaves: organs that increase the surface area of vascular plants, capturing more solar energy for photosynthesis In terms of size and complexity, leaves can be classified as microphylls and megaphylls. All lycophytes have microphylls, small leaves with only a single unbranched vein. These leaves probably evolved as small outgrowths on the surface of stems, supported by single strands of vascular tissue. All other vascular plants have megaphylls, leaves with a highly branched vascular system. 1 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTES  A branched vascular system can deliver water and minerals to the expanded leaf.  can also export larger quantities of sugars from the leaf. Megaphylls support more photosynthetic activity. only with vascular tissue do you have true leaves, stems, and roots sporophyte dominant  vascular tissue is usually only found in the sporophyte generation seeds (when present) are highly resistant structures that increase ability of developing embryos to survive on land divided into seedless and seed-forming groups; seed-forming phyla covered in future outlinesII. Seedless Vascular Plants (ferns and fern allies) sporophyte dominant and can grow independent of gametophyte in all gametophyte small, reduced, but still able to grow independent of sporophyte in all importance: dominated land during Carboniferous Period (354-290 million years ago), becoming a source of coal coal is incompletely decomposed, highly compressed, carbon-rich rock derived mainly from the bodies of ancient seedless vascular plants (a type of “fossil fuel”) fossil coal swamps are full of extinct plants coal is a vital source of energy; burned for heat and for producing electricity (over half of U.S. electric production) at least 3 extinct phyla represented in the fossil record; one will be covered, Phylum Rhyniophyta New phylogenies define 2 phyla with living members – Lycophyta (club mosses, quillworts and spike mosses) and Pterophyta (ferns, horsetails and whisk ferns).  Older classification has 4 phyla. We use this for the course, and also for it to be consistent with your lab manuals. The textbook says otherwise. Phylum Lycophyta Phylum Pterophyta  Phylum Psilophyta (some group with Pterophyta; do fall in a clade with that group and Arthrophyta) Phylum Arthrophyta (some group with Pterophyta; do fall in a clade with that group and Psilophyta)2 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTESIII. extinct Phylum Rhyniophyta – oldest vascular plant fossils (Cooksonia, 420 MYA) branching axis; no leaves or roots only a few centimeters tall sporangia at ends of branches appearance much like that of modern-day whisk ferns homosporous – only one spore type, so only one gametophyte typeIV. Phylum Lycophyta – club mosses, quillworts and spike mosses3 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTES  ~1000 living species; worldwide, but most in tropics and moist temperate regions; many species endangered includes “resurrection plants”. What are they ? fossil record includes tree-like forms that died out about 270 MYA apparently evolved separately from the other seedless vascular plants small, resembling mosses (but vascular with dominant sporophyte) leafy stems usually less than 30 cm long their leaves are also called microphylls, with very little vascular tissue (just a single vein); other vascular plant leaves have much more complex vascular tissue networks homosporous and heterosporous genera heterosporous – plant makes two types of meiospores, resulting in two types of gametophytes megaspore is larger of the two; grows via mitosis into the female gametophyte microspore is smaller of the two; grows via mitosis into the male gametophyte sexual reproduction similar to that of ferns sporangia grow from specialized leaves called sporophylls; sporophylls are clustered in a cone-like strobilusV. Phylum Pterophyta – ferns somewhat complicated phylogeny; we will visit the tree of life in class to discuss this fossils date to as long as 375 MYA (important fossil fuel source)  ~12,000 living species; throughout world, but ¾ of species tropical most leafy, but some tree ferns most are homosporous, but some are heterosporous life cycle similar to moss except decreased gametophyte, independent and dominant sporophyte gametophyte  germinating spore divides by mitosis and forms multicellular protonema  protonema grows into mature gametophyte called prothallus . typically heart-shaped; mostly one-cell thick . has rhizoids4 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTES  gametes produced in male antheridia and female archegonia on same or separate prothalli sperm made in antheridia swim to archegonia (using flagella; need outside water source to swim in) sperm unites with egg, forming diploid zygote zygote undergoes mitotic divisions and develops into sporophyte  sporophyte grows out gametophyte and takes over (larger, vascular, photosynthetic, responsible for all of own nutrition)  typically have horizontal, underground stem (rhizome)  leaves (called fronds) develop from rhizome as coiled “fiddleheads”  form stalked sporangia in clusters called sori, typically on the backs of fronds spore mother cells in sporangium produce haploid spores at maturity, outer covering of sporangium snaps off, catapulting spores spore in right (mainly moist) environment will germinateVI. Phylum Psilophyta – whisk ferns probably form a monophyletic group with ferns and horsetails; some group these within the fern phylum simplest living vascular plants 5 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTES  no true roots or leaves – leaf-like enations and such sometimes present forking green stems (photosynthetic; true stems) sexual reproduction much like ferns (have antheridia and archegonia, swimming sperm that need outside water, etc.) all are homosporous like ferns, sporophyte is dominant generation gametophytes small, colorless in soil beneath sporophytes associated with fungi saprobic or parasitic some have elements of vascular tissue (only gametophytes known to have this) tropical and subtropical only 6 known living speciesVII. Phylum Arthrophyta – horsetails (alternative phylum names: Sphenophyta; Equisetophyta) probably form a monophyletic group with ferns and whisk ferns; some group these within the fern phylum 15 known living species, all in genus Equisetum most <1 m tall, some 3 m tall; widely scattered in damp regions throughout the world fossil record back to 300 MYA once much more diverse and dominant fossil record includes tree-like forms as tall as 30 m sporophyte dominant branching underground rhizomes with roots at their nodes hollow, ribbed, jointed, photosynthetic stems whorls of scale-like, nonphotosynthetic leaves at nodes on stems some have whorls of photosynthetic branches at nodes as well stems hollow silica deposits in some epidermal cells (stiffens; protects from predators) some are called “scouring rushes” because they were used by pioneers for scrubbing dishes most are homosporous6 of 7 BIOL 1030 – TOPIC 5 LECTURE NOTES  sexual reproduction similar to that of ferns sporangia on underside of stalked structures called sporangiophores sporangiophores are clustered in a cone-like strobilus at a stem tip7 of 7

Topic 5: Seedless Vascular Plants (Ch. 29)

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