Plant Taxonomy

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Lecture 1

• Plant Taxonomy
• Global Floristic Realms
• Life form classification

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Biological Kingdoms

• Monera
• Protista
• Fungi
• Animalia
• Plantae

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Taxonomic Hierarchy

• Kingdom
• Phylum (Division)
• Class
• Order
• Family
• Genus
• Species

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An Example of the Taxonomic Hierarchy
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A Plant Example
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Comparison
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Global Floristic Realms

• Regions that differ fundamentally from one
  another in the types of vegetation found there.

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Global Floristic Realms
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Angiosperms and Gymnosperms

• Gymnosperms are phylogenetically older.
• Angiosperms are the youngest branch of the plant
  kingdom.

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Hemispherical Differences

• Northern Hemisphere
• Pinaceae
• Pinus (Pine)
• Abies (Fir)
• Picea (Spruce)
• Larix (Larch)
• Taxodiaceae
• Taxodium (Cypress)
• Sequoia
• Cupressaceae
• Thuja (Eastern White Cedar)
• Juniperus (Juniper)

• Southern Hemisphere
• Podocarpaceae
• Cupressaceae

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Pinus
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Angiosperm Differentiation

• Much more sharply differentiated among floristic
  realms than are the gymnosperms.
• Main development occurred during the Tertiary (65
  2 million years ago).
• Occurred after the continents had separated.

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The Holarctic

• Angiosperms in the northern hemisphere are fairly
  similar.
• North America and Greenland didnt separate from
  Eurasia until the Pleistocene (c. 2 million b.p.)

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Raunkiaer Classifications
Physiognomic method based on the height above
ground of the perennating buds. This
classification is based on the assumption that
species morphology is closely related to climatic
controls.

• Phanerophytes
• Chamaephytes
• Hemicryptophytes
• Cryptophytes
• Therophytes

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Phanerophytes

• Species with perennating buds emerging from the
  aerial parts of the plant.
• Megaphanerophytes (gt 30m)
• Mesophanerophytes (8 30 m)
• Microphanerophytes (2 8 m)
• Nanophanerophytes (lt 2m)

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Chamaephytes

• Species with perennating buds borne on aerial
  parts close to the ground (below 2m)
• Suffruticose chamaephytes after the main growth
  period, upper shoots die so that only the lower
  parts of the plant remain in the unfavorable
  period.
• Passive chamaephytes at the onset of adverse
  conditions, shoots weaken and fall to ground
  level, becoming procumbent. This gives them some
  protection from environmental stress.
• Active chamaephytes shoots are only produced
  along the ground and remain so in the unfavorable
  season.
• Cushion chamaephytes a modification of passive
  types where shoots are arranged so close together
  that they cannot fall over and the close packing
  of all shoots forms a cushion.

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Hemicryptophytes

• All above-ground parts of the plant die back and
  buds are borne at ground level.
• Protohemicryptophytes leaves become better
  developed up the stem of the plant. Poorly
  developed leaves protect the bud in early stages
  of growth.
• Partial rosette plants the developmed leaves
  form a rosette at the base of the plant in the
  first year of growth. The following year an
  elongated aerial shoot may form.
• Rosette plants leaves are restricted to a basal
  rosette with an elongated aerial shoot, which is
  exclusively flower-bearing

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Cryptophytes

• Plant species with buds or shoot apices which
  survive the unfavorable period below ground or
  under water.
• Geophytes plants with subterranean organs such
  as bulbs, rhizomes and tubers from which shoots
  emerge in the next growing season.
• Helophytes plants with their perennating buds in
  soil or mud below water and which produce shoots
  reaching above water.
• Hydrophytes species with buds which lie
  underwater and survive the unfavorable season by
  budding from rhizomes under water or from
  detached vegetative buds which sink to the
  bottom.

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Therophytes

• Plants that survive the unfavorable period as
  seeds.

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Raunkiaer Examples
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Biological Spectra
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SavannaOlokomeji Forest Reserve, Nigeria
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Tropical RainforestBritish Guiana