Still trying to understand plant names

So I have a table which lists the ranks of plant hierarchy and how to recognize which name belongs to which rank.  Cool, but I still wanna know why a plant falls under a particular rank, and what that rank name really means.

The history of plant classification

I started researching the history of plant classification, curious how it even came to be. Here’s what I’m picking up so far:

There are a lot of things in this world. A lot. Especially when it comes to living things like plants and animals. So many in fact that long ago, a classification system was developed in an attempt to classify these things, and has been updated and improved on ever since.

Aristotle (384-322 B.C.) is credited with laying out the ground work for the first division of organisms.  This included a two kingdom system: Plants or Animals. These were further broken down into categories such as whether an animal walked, flew, or swam. This system was used into the 1600’s.

In the 18th Century, Carolus Linnaeus (1707-1778) further added to Aristotle’s system, but is best known for his proposed naming convention. He designed a system called binomial nomenclature, or “two-name naming system” which gave each organism two names, much like people have a first and last name. The first name is the genus (always capitalized), followed by the species (always lower case). To be written correctly, this “scientific” name is always underlined or italicized. Check out the table below for examples:

Common name Genus Species Scientific name
Human beings Homo (man) sapiens (wise) Homo sapiens
Corn Zea (cereal, grain) mays (life giver) Zea mays

In 1969, R. H. Whittaker proposed a 5 kingdom system, dividing complex organisms by forms of nutrition. (Note: this system does not include Lichens, which are a combination or algae and fungi.)

Kingdom Form of nutrition
Plantea Photosynthesis
Animalia Ingestion of solid foood
Fungi Absorption of nutrients in solution
(Divided simple organisms on basis of cell type)
Monera (bacteria) Prokaryotes (lacks membrane bound nucleus, mitochondria, or any other membrane bound organelle.)
Protista (algae, sponges, slime molds) Eukaryotes (“true nucleus”; contains a nucleus and membrane bound organelles.)

Plant Kingdom – Breaking It Down

The plant kingdom is divided into 12 phyla according to

  • modes of reproduction
  • complexity of tissue

These phyla can be divided into four main groups:

Group Phyla Notes
Non-vascular Simplest plants. Reproduce by spores instead of seeds. Lack the vascular tissue to grow large.
Vascular, non-seed Examples: Ferns
Gymnosperms – “naked seeds”
  • Have vascular tissue
  • Bear seeds not enclosed in fruits
  • Softwoods
  • Narrow leaf
  • Mostly evergreen

Examples: Conifers, Ginkgos, Cycads

Angiosperms – “vessel seeds” Magnoliophyta
  • Bear seeds enclosed within fruit
  • Defining characteristics include flowers and carpels
  • Hardwoods
  • Broadleaf

Examples: Deciduous, Maples, Oaks

Beginning to classify plants by what we see

It makes sense to start my classification attempts with plants I am most familiar with and see most often. These plants are angiosperms which fall under the phylum Magnoliophyta, which can be divided into two classes:

  • Magnoliopsida (Dicots)
  • Liliopsida (Monocots)

Monocots and Dicots

Monocots:

  • Seed with one cotyledon (seed leaf)
  • Flower parts in mulitples of threes
  • Leaf with parallel veins
  • Vascular cambium absent
  • Vascular bundles of stem in a scattered arrangement
  • Vascular tissue of root arranged in a ring
  • Pollen grains with one aperture
  • Examples:
    • garlic
    • corn
    • onion
    • lilies
    • orchads
    • grasses

Dicots:

  • Seed with two cotyledons
  • Flower parts in mulitples of fours or fives
  • Leaf with netted veins
  • Vascular cambium present (in older plants)
  • Vascular bundles of stem arranged in a ring
  • Vascular tissue of root arranged in center
  • Pollen grains with three apertures
  • Examples:
    • tomatoes
    • peppers
    • broccoli
    • apples
    • roses
    • geraniums

No need to limit your new classification knowledge to just  plants. You can use what you know about Angiosperms versus Gymnosperms to start identifying just about any tree you see.

Or, start with what we learned in the previous post. Pick the scientific name of your favorite plant and start with its taxonomy to learn the meaning of its name. For example:

The taxonomy of Zea mays (corn)

Rank Meaning How it relates
Domain: Eukarya “True nucleus”
  • Mulitcellular
  • Undergoes mitosis and meiosis
  • Autotrophic
  • Has a cell wall made of cellulose
Kingdom: Plantae “Of plant”
  • Contains chlorophyll
  • Undergoes photosynthesis
Phylum: Magnoliophyta “Broad plant “(Broad leaf)
  • Flowering plant
  • Broadleaf
  • Vascular
  • Ovales enclosed in an ovary
Class: Liliopsida “Lily appearance”
  • Monocot
  • Parallel veined leaves
Order: Poales “Belonging to fodder order”
  • Flowers usually small, surrounded by bracts
  • Flowers usually arranged in inflorescences
  • Seeds usually contain starch
  • Fibrous leaves
Family: Poaceae “Grass family”
  • Hollow stems
  • Leaf sheath typically open
  • Leaves usually arranged in two rows on side of stem
  • Fruit usually resembles kernels of corn and tiny ovals
Genus: Zea “Single-grained wheat”
  • Long strap-like leaves
  • Roots typically fibrous
  • Separate staminate and carpellate flower cluster
Species: mays “Life sustaining”
  • Long, solid cane-like stalk
  • Distinguished by it’s female inflorescence (corncob)

By following the ranks of Zea mays,  I was able to learn a lot about classification and picked up some new terminology. However, my greatest lesson learned is that classification can also depend on who you’re talking to.  For instance, some resources sited that the class could be either Liliopsida or Magnoliopsida.  I don’t know enough at this point to argue either way, but it appears that I’m not the only one.

Happy classification!

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