lecture 6 grasses Flashcards
(33 cards)
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
