there are two classes of grasses, distinguished by a fundamental property of
photosynthesis (abbreviated C3 and C4). Many prairie grasses have the C4 pathway,
and because of this are able to proliferate in warmer parts of the summer when
other plants are suffering from moisture stress. For the most part, prairie
grasses are warm season grasses, and savanna grasses are cool season grasses.
The C3/C4 differentiation is a good example of evolution in action, and
botanists have been able to explain at a fairly fundamental level how these two
kinds of grasses differ.
I recently spent some time putting together a table that sorts out these two
kinds of grasses, based on an extensive review that was published by S.S.
Waller and J.K. Lewis in the Journal of Range Management (1979; vol. 32,
pp. 12-28). Note that my table is just a subset of that of Waller and Lewis since they have a lot of grasses that we are not familiar with here in the Midwest.
As I indicated, the C3/C4 phenomenon is an interesting evolutionary development
that relates to the ability of plants to tolerate drought. The explanation is
fairly sophisticated, but the Wikipedia pages on this are very good. See this link. (What would be
do without Wikipedia?)
Essentially, the C4 pathway permits plants to carry out photosynthesis during
warm (or hot) summer conditions, making them able to outcompete C3
plants.
Note that in our temperate climate, the only C4 plants are grasses, but in the
tropics many broadleaf plants have the C4 pathway.
It is interesting that although C4 plants represent only 5% of the Earth’s
plant biomass, and only 1% of the known plant species, they account for about
30% of terrestrial carbon fixation.
|
Genus
|
Common name
|
C3
|
C4
|
|
Agropyron
|
Wheat grass (not agricultural wheat, which is Triticum)
|
*
|
|
|
Agrostis
|
Bent grass
|
*
|
|
|
Andropogon
|
Big bluestem
|
|
*
|
|
Avena
|
Agricultural Oats
|
*
|
|
|
Bouteloua
|
Side oats
|
|
*
|
|
Bromus
|
Brome
|
*
|
|
|
Calamagrostis
|
Blue-joint
|
*
|
|
|
Dactylis
|
Orchard grass
|
*
|
|
|
Deschampsia
|
Hair grass
|
*
|
|
|
Dichanthelium (formerly Panicum)
latifolium; leibergii; oligosanthes; praecocius
|
Panic grass
|
*
|
|
|
Digitaria
|
Crab grass
|
|
*
|
|
Echinochloa
|
Barnyard grass
|
|
*
|
|
Elymus
|
Wild rye
|
*
|
|
|
Eragrostis
|
Love grass
|
|
*
|
|
Festuca
|
Fescue
|
*
|
|
|
Glyceria
|
Manna grass
|
*
|
|
|
Hordeum
|
Barley
|
*
|
|
|
Koeleria
|
June grass
|
*
|
|
|
Leersia
|
Rice cut grass
|
*
|
|
|
Lolium
|
Perennial rye grass
|
*
|
|
|
Muhlenbergia
|
Muhly grass
|
|
*
|
|
Oryza
|
Rice
|
*
|
|
|
Panicum virgatum
Panicum capillare
Some other species of Panicum are C3 grasses
|
Switch grass
Witch grass
|
|
*
|
|
Paspalum
|
Paspalum grass
|
|
*
|
|
Phalaris
|
Reed canary grass
|
*
|
|
|
Phleum
|
Timothy
|
*
|
|
|
Poa
|
Blue grass
|
*
|
|
|
Pragmites
|
Common reed grass
|
*
|
|
|
Schizachyrium
|
Little bluestem
|
|
*
|
|
Secale
|
Cereal rye
|
*
|
|
|
Setaria
|
Foxtail
|
|
*
|
|
Sorghastrum
|
Indian grass
|
|
*
|
|
Sorghum
|
Broom-corn
|
|
*
|
|
Spartina
|
Cord grass
|
|
*
|
|
Sphenopholis
|
Wedge grass
|
*
|
|
|
Sporobolus
|
Dropseed
|
|
*
|
|
Stipa
|
Needle grass
|
*
|
|
|
Triticum
|
Wheat
|
*
|
|
|
Zea
|
Corn
|
|
*
|