Sunday, August 16, 2015

Grasses

lawns
Note the grasses.
Grasses. They're everywhere, but often unnoticed.

hay field
Haying a native grassland in Nebraska
But if a grass were to tell about the world it would point out:

1) There are a LOT of grasses. 11,337 species, making them, the Poaceae also called the Graimeae, the 4th largest plant family.


Only the orchids (Orchidaceae 27,800 species), sunflowers and daisies (Asteraceae 23,600) and peas and beans (Fabaceae 19,560 species) have more species, out of about 465 families of flowering plants and a total of more than 352,000 plant species.

grasses in Argentina
grasses in Argentina
2) Grasses are the only plant family found on every continent.

Except Antarctica, but there are no plants on Antarctica, so a grass telling this story wouldn't consider it. It is not as if some stupid daisy grows there and no grass does.

3) Grasses are the only plant family with an ecosystem named after them. Grasslands! link to map (you'll have to scroll down until you see the map).

Note the absence of orchidlands or sunflowerlands or bean lands... That's because grasses are the dominant--most common, most numerous--family in the worldwide herbaceous ecosystem that is therefore named grassland.

California grassland

Grasslands have local names: prairie in North America, steppe in Eurasia, pampa in South America, but all of those are grasslands, grass-dominated ecosystems. And similar ones occur in tropical and temperate Africa, Asia and Australia.

"Forests," notes the grass a bit arrogantly, "are mixes of trees of many families--oaks, elms, maples, each of those trees is in a different plant family."

grasses


"What," I ask the grass, "is the source of your success?"

"Ah," it tells me, "it is the underground meristem!"

(A meristem is a growing point, the spot from which growth is initiated. See diagrams  grass-leaf #1grass leaf  #2non-grass. Of course there is additional terminolog for the exact type and location of meristem.)

"Because grasses have our meristems below ground, you can mow the grass! You can't mow tomatoes--their meristems are on the tips of their branches! Mowing would set them wa-a-ay back.
But the mowed grass's new growth just pushes up from the meristem, scarcely interrupted. Kinda like the way hair and nails grow on humans.

asters in the grass
the asters are much more susceptible to damage
due to grazing or fire than the grasses
"Underground meristems are the key to our success. When big herds of animals--wildebeasts, bison or cattle--graze on grasses, all that is cropped is the leaf. The meristem is unhurt. Not so for most other plants in the grassland. So we are less injured by grazing and come back faster.

"AND!!!!!!" (it waves its leaf tips emphatically) "fire is like grazing or mowing. A fire in a grassland only sets us back a few days. Up the blades come again, the soil having protected the meristem. In most grasslands, fires favor grasses at the expense of other plants."

prairie fire
prairie fire
"Thank you for telling me all this, " I said. "Grasses are impressive."

"Wait," it said, agitated, "you don't know the whole of it yet. The grains that humans depend upon--they are grass seeds! Rice, wheat, corn, oats, barley, rye, millet, sorghum!!! Humans love grass seeds.

"AND...humans are forever turning land that was forest or swamp into grasslands. What after all, is a cornfield, a wheatfield or a rice paddy but a field of grass?

cornfield
A corn field is a grassland.
"Not to mention suburban homes surrounded by lawns of ... grass! And you make play areas for outdoor activities on a carpet of grass, not orchids or dandelions!

grass lawn
city park lawn
"Have some respect next time you walk on the grass!"


Comments and corrections welcome.

Numbers per family: Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 12, July 2012 [and more or less continuously updated since]."  http://www.mobot.org/MOBOT/research/APweb/. Accessed August 14, 2015.


Kathy Keeler









1 comment:

  1. Interesting post! I had never thought about that: "Grasses are the only plant family with an ecosystem named after them"

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