Broadleaf Woodoats (Chasmanthium latifolia) Introductory Grass Identification Workshop University of Houston Coastal Center 23 September 2017 1 Introduction This 5 hour workshop is an introduction to the identification of grasses using hands- on dissection of diverse species found within the Texas middle Gulf Coast region (although most have a distribution well into the state and beyond). By the allotted time period the student should have acquired enough knowledge to identify most grass species in Texas to at least the genus level. For the sake of brevity grass physiology and reproduction will not be discussed. Materials provided: Dried specimens of grass species for each student to dissect Jewelry loupe 30x pocket glass magnifier Battery-powered, flexible USB light Dissecting tweezer and needle Rigid white paper background Handout: - Grass Plant Morphology - Types of Grass Inflorescences - Taxonomic description and habitat of each dissected species. - Key to all grass species of Texas - References - Glossary Itinerary (subject to change) 0900: Introduction and house keeping 0905: Structure of the course 0910: Identification and use of grass dissection tools 0915- 1145: Basic structure of the grass Identification terms Dissection of grass samples 1145 – 1230: Lunch 1230 - 1345: Field trip of area and collection by each student of one fresh grass species to identify back in the classroom. 1345 - 1400: Conclusion and discussion 2 Grass Structure spikelet pedicel inflorescence rachis culm collar internode ------ leaf blade leaf sheath node crown fibrous roots 3 Grass shoot. The above ground structure of the grass. Root. The below ground portion of the main axis of the grass, without leaves, nodes or internodes, and absorbing water and nutrients from the soil. Crown. The persistent base of a perennial grass. Culm (Stem). A major division of the plant body in contrast to root and leaf, distinguished from both by certain anatomical features and commonly also by general aspect; the main axis or axes of a plant; the portion of the plant axis bearing nodes, leaves, and buds and usually found above ground. - Rhizome. A horizontal, underground stem with modified leaves at the nodes. - Stolon. A horizontal, above-ground stem with modified leaves, nodes, internodes, and axillary buds. Node. The joint of a stem; the region of attachment of the leaves. Leaf sheath. The tubular basal portion of a leaf that encloses the stem. Generally there is a ligule at the inside (adaxial) junction of the leaf sheath and the leaf blade. The ligule is a very reliable vegetative characteristic for grass identification. In 4 some grasses an ear-shaped appendage called an auricle occurs in pairs laterally at the base of the leaf blade and laterally at the sheath apex in others. Its function is to hold the open sheath. ligule membranous ligule. ligule ligule Ligule with hairs. Ligule with sheath closed. Ligule with ciliated ligule membrane Auricle Leaf blade. The flattened, expanded portion of leaf above the sheath. Collar. The outer side of a grass leaf at the junction of the blade and sheath. Inflorescence. The flowering portion of a shoot; in grasses, the spikelets and the axis or branch system that supports them, the inflorescence being delimited at the base by the uppermost leafy node of the shoot. Grass inflorescences are delimited by the uppermost culm leaf or portion thereof. By 5 this definition, multiple inflorescences can occur on a single culm. The spike, spicate raceme, and raceme inflorescences do not have branches arising from the central axis (rachis). With these inflorescences the spikelets either are attached directly or individually pedicelled (or stalked) upon the central axis. A panicle inflorescence is anywhere the spikelets are not sessile or individually pediceled on the main axis. S CA Switch Grass CA – Central Axis S - Spikelet A spike inflorescences are those in which the spikelets are sessile on the centreal axis or rachis.A raceme inflorescence has pedicels supporting single spikelets, with the pedicel attached to the central axis. 6 Cheatgrass CA S A panicle of spicate primary unilateral branches is a common modification of the typical panicle inflorescence. Branches developing from the nodes at the central axis of the inflorescence are called primary branches. Spikelets on this inflorescence type are racemose (subsessile) or spicate (sessile) on the primary branch and make the branch appear spikelike, hence the term "spicate." The spikelets are attached along one side of the branch and give the branch a unilateral or one-sided appearance. Panicles with spicate primary unilateral branches may be described by the arrangement of the branches using modifiers such as alternate, digitate, subdigitate, or verticillate. PS CA S PS – Pedicelled Spikelet CA – Central Axis SS – Sessile Spikelet Little Bluestem 7 A spicate raceme has an unbranched central axis with sessile spikelets and short pedicellate spikelets (PS). PS S CA CA Wild Barley S CA Sideoats Gramma Panicle of alternate spicate primary unilateral branches 8 S CA Panicle of subdigitate spicate unilateral unilateral branches. S CA Panicle of verticillate spicate primary unilateral branches. Rachis or main axis of the inflorescence. The central stem or branch of the culm or inflorescence in which parts of the grass are arranged. Pedicel. The stalk of a single spikelet Spikelet. The basic unit of the grass inflorescence, usually consisting of short axis, the rachilla, bearing 2 empty bracts called the glumes, at the basal nodes and 1 or more florets above. - The rachilla. The main axis of a grass spikelet. 9 Floret. As applied to grasses, the lemma and palea with the enclosed flower; may be perfect, pistillate, staminate, or sterile. reduced (neuter) floret awn palea stigma rachilla anther floret lemma ovary lodicule second glume first glume pedicel Glumes. The pair of bracts usually present at the base of the grass spikelet. The first glume is lower. Both glumes are usually present, but occasionally the first may be reduced in size or completely absent or both partially fused. Lemma. Part of the second series of bracts of the spikelet. The lemma is probably the most reliable and frequently used character in grass in identification. It is always present and has a high degree of stability within a genus. Lemma texture, shape, 10 number of nerves, awn development, and surface features are used extensively in identification. - Nerve. A simple vein or slender rib of a leaf or bract (glumes, lemma, and/or palea). Palea. Part of the second series of bracts of the spikelet. Usually 2-nerved and 2- keeled and often enclosed by the lemma. - Keel. A prominent dorsal ridge, like the keel of a boat. Glumes and lemmas of laterally compressed spikelets are often sharply keeled. Ovary. Part of the pistil that contains the ovules. - Pistil. The female (seed-bearing) structures of the flower, ordinarily consisting of the ovary, stigma, and style. - Ovules. The structure that develops into the caryopsis (seed). - Caryopsis. The characteristic grass fruit (seed) Stigma. The part of the ovary or style that receives the pollen for effective fertilization. Anthers. The pollen-bearing part of a stamen. 11 Workshop Species Dissection Genera Group Key Group A Spikelets surrounded by a bur-like involucre of prickly spines or smooth scales. Plants monoecious; burlike structure (fascicle) composed of bristles or flattened spines fused for more than ½ their length; spines sharp enough to puncture flesh Coastal Sandbur (Cenchrus spiniflex) – Annual, mostly with tall, coarse, stiffly erect culms. Ligule a fringe of hairs. Spikelets enclosed in fascicles with more than 1 whorl of flattened inner bristles usually 1-3 mm wide at base, 8-43 bristles, disarticulating at maturity. Glumes thin, membranous, unequal. Lower glume 1 to 3-nerved, the upper 1-7 nerved. Lemma of the sterile floret thin, 1-7 nerved, equaling or exceeding the upper glume. Palea of the sterile floret about equaling the lemma. Lemma of the fertile floret thin, membranous, 5-7 nerved, tapering to a slender, usually acuminate tip, the margins not inrolled. spikelet palea lemma upper lower floret glume glume fascicle Fascicle cut opened to show seed. 12 Group B. Spikelets unisexual, staminate; pistillate spikelets usually conspicuously different. Plants monoecious, > 2m tall Gammagrass (Tripsachum dactyloides) – Large cespitose perennials with stout, thick-based culms and usually broad, flat blades. Inflorescence a spikelike raceme or series of 2 to few spikelike racemose branches bearing staminate spikelets above and pistillate spikelets below. Staminate spikelets 2-flowered, in pairs on one side of a continuous rachis. Pistillate spikelets below the staminate and on the same rachis, single, sessile, an partially embedded on the rachis. Glumes of the staminate spikelet flat, several-nerved, relatively thin. Glumes of the pistillate spikelet hard and boney, fused with the rachis and tightly enclosing the rest of the spikelet. Lemmas of the sterile and fertile florets thin and membranous, awnless, often reduced. Staminate portion of the rachis deciduous as a whole, the pistillate portion breaking up at the nodes into beadlike units. staminate spikelet pedicel pistillate staminate spikelet spikelet rame internode lower glume pistillate spikelet 13 Group C Spikelets in pairs of 1 sessile and 1 pediceled; lower glumes large and enclosing spikelet. 1. Spikelets all alike and fertile Big Bluestem (Andropogon gerardii). Cespitose perennials with usually stiffly erect culms, rounded or flattened and keeled sheaths, and flat or folded blades; ligules membranous. Flowering culm little-branched above the base. Each culm or branch terminated by an inflorescence of 2 to several racemose branches. Sessile spikelets with awn 8-25 mm long; rhizomes sometimes present, the internodes usually <2 cm long. Pediceled spikelet well developed. Disarticulation in the rachis, the sessile spikelets falling attached to the associated pedicel and section of the rachis. Glumes large, firm, awnless. Lemmas of the sterile and fertile florets membranous, lemma of the fertile floret awned. 14 1.