lecture 6 grasses Flashcards
Three Characteristics of a Grass
- The flowers lack petals and are borne between bracts in a leafless inflorescence
- The leaves are flat, long and slender, and form a sheath around the stem
- The stems are round, generally hollow, and somewhat swollen at the nodes
The current system of plant taxonomy is based primarily on ___________
___________,more than any other character, that really define the grass species
reproductive structures
flowers
Grasses are difficult to identify because many of their ___________and ____________structures are unique to the family
reproductive and vegetative
How Grass Plants Are Put Together (Vegetative Structures)
All grasses are ______________ plants (or _________)
This means that grasses have only one _________, which is the first or “______” leaf that emerges from a seed
monocotyledonous; monocots
cotyledon; seed
the first structure that emerges from a grass seed is a cylindrical, tube-like structure called a ________
it is from within this tube that the fragile cotyledon grows upward to the surface and unfurls
coleoptile
As the grass plant continues to grow,______________, each of which emerges from within the leaf that preceded it
leaves are formed
The characteristics of the _______ are commonly used for grass identification
blades
Characteristics of blades
– Blade width
– Whether the expanded blade is rolled or flat
– Whether or not the midrib is distinctly visible on the upper surface
– Presence or absence of hairs
– Whether newly emerging blades are rolled or folded
The ______ or ________ part of the leaf (the part that wraps around the stem) is termed the ______
“tube” or “sleeve”
sheath
Commonly used sheath characteristics:
– The degree to which the sheath is open (the edges merely overlapped) or closed (the edges fused together into a seamless sleeve) and the
– Presence or absence of hairs
The entire leaf, then, extends upwards from a ______, up the sheath, and outward to the tip of the blade
node
The ____________ and _________ are also important characteristics = ________ of the leaf
structures at the junction of the blade and sheath
collar of the leaf
Two types of structures that grasses may have in this region
– Auricles
– Ligules
_______ are finger-like projections of the upper edges of the sheath that appear to wrap around the stem
The ______ or ______ of these paired structures is a useful identification feature
Auricles may be _______, _______, or _______ and ________ or fringed with hairs
auricles
presence or absence
short,long, or absent and smooth
_________ are small projections located between the blade and the stem
To best observe this structure, _____________________, and it will pop into view
ligule
gently pull the blade away from the stem
The ligule may be:
- completely membranous
- a ring of hairs
- hairs that form a fringe on a membranous base
The type of ligule, as well as its _______, __________, and ___________ of the leading edge are key identification features
length, overall shape, amd texture
Reproductive structures
Individual flowers of grass plants are called _______
A typical floret has __________ and a ________ with _________ at the tip
florets
three stamens and a single ovary with two stigma
The ovary is borne between _______________
– The outer bract is the _________
– The usually smaller, inner bract is the _________
These structures are usually green when the plant is in flower, becoming ______ to ________ as the seed ripens
two tiny, leaf-like bracts
lemma
palea
chaffy to leathery
The ________, ________, and _________ of the palea and lemma help in identification
In addition, lemmas are frequently
length, texture and number of major veins (nerves)
awned
Florets may be borne _______, or in clusters of up to ____ or more
These clusters of florets are termed _________, each with two additional bracts at the base
These bracts are the ______, which may be variously awned and nerved
singly; 14
spikeletes
glumes
Spikelets will break away from the stem or disarticulate in one of two ways:
– Above the glumes, leaving the empty glumes on the plant after the spikelets have dropped
– Below the glumes, in which case the glumes remain attached to the spikelet as it drops
Inflorescence
A _________ inflorescence is anywhere the spikelets are not sessile or individually pediceled on the main axis.
A ________ inflorescences are those in which the spikelets are sessile on the central axis or rachis.
A _________ inflorescence has pedicels supporting single spikelets, with the pedicel attached to the central axis.
panicle
spike
raceme
Eleusine indica (L.) Gaertn.
Goose grass/Paragis/bila-bila
Saccharum spontaneum L.
Wild sugarcane/ talahib
Imperata cylindrica (L.) P.Beauv
Cogon grass
Saccharum officinarum
Sugar cane
Axonopus compressus (Sw.) P.Beauv.
Carabao grass
Cymbopogon nardus (L.) Rendle.
Citronella grass
Bambusa blumeana
Kawayang tinik
Zea mays (L.)
Corn
Oryza zativa (L.)
Rice
Coix lacryma-jobi L.
Job’s tears/ adlai
