BASIC GRASS
TERMINOLOGY
Illustrated
Rushes
Sedges
Grasses
Culms (stems)
(1) Ligule
(2) Auricles
Hordeum (barley)
Fringe of Hairs Ligule
Panicum
Phalaris arundinacea
Poa pratensis
Bouteloua hirsuta
Closed Sheaths
Bromus briziformis
fused sheath margins
Closed Sheaths
Glyceria grandis
Habit and Duration
“Lifestyles of the Rice and Fonio”
Turf-forming
(rhizomatous and/or
stoloniferous)
Phalaris arundinacea
Cespitose
Festuca idahoensis
Sporobolus cryptandrus
c Richard Old
The Grass Flower and
the Primary Inflorescence
Spikelet
Calamagrostis
Sterility
Upper florets sterile
Lower florets sterile
Spikelet Compression
Spikelet Disarticlation
•
•
above the glumes
below the glumes
The Secondary Inflorescence
True Spike
Elymus repens (formerly Agropyron)
Lolium perenne
Raceme-like
Pleuropogon refractus
Panicle
Phalaris arundinacea
Glyceria grandis
Panicle
Puccinellia
Spike-like Panicle
Phleum (l)
Alopecurus (c)
Koeleria (r)
Grass Taxonomy
Taxonomic classification
Category
Name
Characteristics
Kingdom
Plantae
Organisms with rigid cellulose cell
walls, chlorophyll a & b, …
Division
Anthophyta
Flowering seed plants
Class
Monocotyledones
Embryo with one seed leaf
Order
Commelinales
Family
Poaceae
Flowers subtend. by 2 bracts, etc.
Subfamily
Pooideae
Multi-flowered spikelets; sterile
florets on top
Tribe
Poeae
Uncertain
Genus
Poa
Panic.; multi-flowered spikelets…
Species
Poa annua
Annual; no to few cobwebby hairs
Trends in Grass Evolution
1. Morphological Simplification through reduction
(minimization and loss) of sexual parts
2. Rapid Speciation
3. Adaptation to drought and open spaces
4. Niche Specialization
5. Chromosomal Diversification: reduction, polyploidy, and
hybridization are rampant (80% of all grasses are
estimated to be polyploid)
notable genetic and
phenotypic plasticity within taxa
6. Convergent and Parallel Evolution in morphological,
physiological, anatomical, embryological, and cytological
characters
important epistemological challenges in
grass systematics
A recent classification of Poaceae recognized twelve subfamilies
(Grass Phylogeny Working Group 2001):
1. Anomochlooideae, broad-leaved grasses; two genera (Anomochloa,
Streptochaeta)
2. Pharoideae, three genera, including Pharus and Leptaspis
3. Puelioideae, a small lineage that includes the African genus Puelia
4. Pooideae, including wheat, barley, oats, brome-grass (Bromus), reed-grasses
(Calamagrostis) and many lawn and pasture grasses; 1000+ spp
5. Bambusoideae, including bamboo; 1000+ spp
6. Ehrhartoideae, including rice (Oryza), wild rice (Zizania)
7. Arundinoideae, including giant reed (Arundo), common reed (Phragmites)
8. Centothecoideae, 11 genera; sometimes included in Panicoideae
9. Chloridoideae, including the lovegrasses (Eragrostis, ca. 350 species, including
teff), dropseeds (Sporobolus, ca.60 species), finger millet (Eleusine coracana),
and the muhly grasses (Muhlenbergia, ca. 175 species) ; 1000+ spp
10. Panicoideae, including panic grass (Panicum), maize (Zea), sorghum, sugar
cane,(Saccharum), most millets, fonio (Digitaria), and bluestem grasses
(Sorghastrum); 1000+ spp
11. Micrairoideae, large clade based on chloroplast and structural data, but no
morphological synapomorphies!
12. Danthonioideae, including pampas grass (Cortaderia)