Grass Plant Structure and Inflorescence Types

Grass Plant Structure

• Grass plants have blades, sheaths, nodes, and spikelets.
• The culm is the stem of a grass plant.
• Rhizomes are horizontal stems, stolons are above ground horizontal stems, and fibrous roots are part of the root system.
• The blade, auricle, ligule, and sheath are components of the grass leaf.

Grass Inflorescence Types

• Spike: A spikelet is attached directly to the main axis.
• Spicate raceme: The spikelets are on pedicels
• Raceme: Spikelets are on pedicels along a central axis.
• Open panicle: A branching inflorescence with spicate branches.
• Specialized panicles: Alternate spicate primaries and digitate, subdigitate, and verticillate spicate primary unilateral branches.

Andropogoneae Inflorescences

• Paired spikelets at each node, including spicate racemes, subdigitate racemose branches, generally alternate branches, and an open panicle.

Spikelet Parts

• Spikelets have a rachilla, florets, awns, palea, stigma, anthers, lemma, ovary, lodicule, and floral axis.
• There are first and second glumes, reduced (neuter) florets, and pedicels. Each spikelet may have 6 or more florets.

Spikelet Parts - Genera and Tribes

• Diagrams of spikelets from specific genera.
• Spikelets represent specific species from Chlorideae, Eragrosteae, Paniceae, and Andropogoneae tribes.

Ligules of Grass Leaves

• Types of ligules: absent, ring of hairs, membranous, ciliate membrane, acuminate, obtuse, acute, truncate, entire, notched, and eorse.

Leaf Attachment and Plant Growth

• Sessile, petiolate, clasping, procumbent, erect, ascending, creeping, and decumbent.

Leaf Arrangement

• Opposite, alternate, and whorled.

Types of Forbs

• Types include acaulescent, caulescent, and horizontal stems, stolon, and rhizome are horizontal stems..

Leaf Types

• Simple (pinnate venation, parallel venation)
• Pinnately compound (3-foliate)
• Palmately compound (3-foliate, 9-foliate)
• Simple (scale-like, needles)
• Types also distinguished by odd even pinnately compound, bipinnately compound, and spine-like stipules.

Leaf Shapes

• Leaf shapes include deltoid, elliptic, linear, lanceolate, oblanceolate, oblong, orbiculate, obovate, ovate, sagittate, spatulate, and filiform.

Leaf Apices

• Leaf apices are characterized by terms like acuminate, acute, cleft, emarginate, obcordate, obtuse, apiculate, rounded, and truncate.

Leaf Margins

• Leaf margins exhibit variations such as ciliate, cleft, crenate, dentate, dissected, double serrate, entire, erose, incised, lobed, pinnatifid, serrate, sinuate, and undulate.

Inflorescence Types

• Spike, raceme, panicle, umbel, compound umbel, cyme, corymb, compound cyme, catkin, and head.

Flower Types

• Flower types include zygomorphic (papilionaceous), zygomorphic, actinomorphic (without petals), actinomorphic (with petals), head (inflorescence type not a single flower).

Asteraceae Head Types

• Head types like radiate, ray flower, disk flower, discoid, receptacle, and vertical sections of radiate ligulate.

Fruit Types

• Fruit types included are fleshy (berry, accessory, drupe), and dry indehiscent (nutlet, achenes).

Dry Dehiscent Fruits

• Follicle, capsule, urticle, silicle (capsule), silique (capsule), loment, legume (coiled) and legume are dry dehiscent fruits.