Fungi and Plants (SYSTEMATICS)

• Fungus Diversity


  • Chytrids (1,000 species)
  • Zygomycetes (1,000 species)
  • Glomeromycetes (160 species)
  • Ascomycetes (65,000 species)
  • Basidiomycetes (30,000 species)

  
• Hyphae


  25 µm
• Zygomycetes


  • They exhibit great diversity of life histories
  • They include fast-growing molds, parasites, and commensal symbionts
  • They are named for their sexually produced zygosporangia
  • Zygosporangia can survive unfavorable conditions
• Life Cycle of the zygomycete Rhizopus


  1. Plasmogamy

  2. Karyogamy

  3. Meiosis

  4. Asexual reproduction

  5. Sexual reproduction
• Some zygomycetes, such as Pilobolus, can actually "aim" their sporangia toward conditions associated with good food sources
• Ascomycetes


  • They live in marine, freshwater, and terrestrial habitats
  • They are defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps
  • They vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels
  • They include plant pathogens, decomposers, and symbionts
  • They reproduce asexually by enormous numbers of asexual spores called conidia

  
• Neurospora


  A model organism with a well-studied genome
• Basidiomycetes


  • They include mushrooms, puffballs, and shelf fungi, mutualists, and plant parasites
  • They are defined by a clublike structure called a basidium, a transient diploid stage in the life cycle

  
• Lichen


  A symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae

  
• Types of lichens


  • Foliose (leaflike)
  • Fruticose (shrublike)
  • Crustose (encrusting)

  
• Lichens


  • The fungal component is most often an ascomycete
  • Algae or cyanobacteria occupy an inner layer below the lichen surface
  • The algae provide carbon compounds, cyanobacteria provide organic nitrogen, and fungi provide the environment for growth
  • The fungi of lichens can reproduce sexually and asexually
  • Lichens are important pioneers on new rock and soil surfaces -- pioneer organisms in ecological succession
  • Lichens are sensitive to pollution, and their death can be a warning that air quality is deteriorating

  
• About 30% of known fungal species are parasites or pathogens, mostly on or in plants
• Some fungi that attack food crops are toxic to humans
• Animals are much less susceptible to parasitic fungi than are plants
• Mycosis


  The general term for a fungal infection in animals
• Fungal Diseases in Plants


  • Corn smut on corn
  • Tar spot fungus on maple leaves
  • Ergots on rye
• Practical Uses of Fungi


  • Food (cheeses, alcoholic beverages, bread)
  • Production of antibiotics (e.g. Penicillium)
  • Biotechnology (e.g. insulin-like growth factor produced in Saccharomyces cerevisiae)
• Penicillium: Fungal production of an Antibiotic


  1. Mold produces antibiotic

  2. Inhibits bacteria growth

  3. Results in a clear area between the mold and the bacteria
• Plant Groups


  • Nonvascular plants (bryophytes)
  • Seedless vascular plants (lycophytes, pterophytes)
  • Seed plants (gymnosperms, angiosperms)
• Nonvascular plants (bryophytes)


  • Commonly called bryophytes
• Seedless vascular plants


  • Can be divided into lycophytes and pterophytes
  • Are paraphyletic, and are of the same level of biological organization, or grade
• Seed


  An embryo and nutrients surrounded by a protective coat
• Seed plants


  • Gymnosperms (naked seed plants including conifers)
  • Angiosperms (flowering plants including monocots and dicots)
• Seed plants form a clade
• Highlights of Plant Evolution

  • Origin of land plants (about 475 mya)
  • Origin of vascular plants (about 420 mya)
  • Origin of extant seed plants (about 305 mya)
• Gametophyte / sporophyte relationships in different plant groups


  • Mosses and other nonvascular plants (reduced, dependent on surrounding sporophyte tissue for nutrition)
  • Ferns and other seedless vascular plants (reduced, independent (photosynthetic and free-living))
  • Seed plants (gymnosperms and angiosperms) (reduced, dependent on gametophyte for nutrition)
• Lycophytes


  • Include club mosses, spike mosses, and quillworts
• Pterophytes


  • Include ferns, horsetails, and whisk ferns
• Increased photosynthesis by seedless vascular plants may have helped produce the global cooling at the end of the Carboniferous period
• The decaying plants of the Carboniferous forests eventually became coal = fossil fuel
• Gymnosperms


  • Bear "naked" seeds, typically on cones
  • Appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems
  • Were better suited than nonvascular plants to drier conditions
  • Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes

  
• Ginkgo biloba


  A gymnosperm with a high tolerance to air pollution and a popular ornamental tree
• Conifers


  • Most are evergreens and can carry out photosynthesis year round
• Giant Sequoia trees can weigh 2,500 tons and live 1,800 - 2,700 years
• Angiosperm Groups


  • Monocots (one cotyledon)
  • Eudicots ("true" dicots, two cotyledons)
• Monocots


  • More than one-quarter of angiosperm species are monocots
• Eudicots


  • More than two-thirds of angiosperm species are eudicots
• Monocot Characteristics


  • Vascular tissue usually arranged in ring
  • Veins usually parallel
  • One cotyledon
  • Root system usually fibrous (no main root)
  • Pollen grain with one opening
  • Floral organs usually in multiples of three
• Eudicot Characteristics


  • Veins usually netlike
  • Two cotyledons
  • Taproot (main root) usually present
  • Pollen grain with three openings
  • Floral organs usually in multiples of four or five
• Plant Evolutionary Relationships: Charophyte green algae are the closest living relatives of land plants