spikelet

A spikelet is the basic unit of the inflorescence in grasses (family Poaceae). It typically comprises two protective bracts called glumes at the base and one or more florets. Each floret is enclosed by a pair of bracts, the lemma (outer) and the palea (inner). The spikelet sits on the rachilla, the neighboring axis, and its internal structure may include lodicules, stamens, and a pistil, depending on the species.

Glumes protect the developing florets and may be fertile or sterile. The number of florets per spikelet varies among species, ranging from a single fertile floret to several, each with its own lemma and palea. The floral parts can differ in size and ornamentation, such as awns on the lemma in many species. These features, along with the arrangement of spikelets on the inflorescence, are important for grass identification and classification.

After fertilization, the grain that develops is a caryopsis, in which the seed is tightly fused to the once-ovular pericarp. The glumes and other spikelet parts may persist around or alongside the mature seed, or they may be shed as the seed matures.

Spikelet morphology and arrangement are highly variable across grasses, contributing to a wide range of inflorescence forms, from simple spikes to complex panicles. Because spikelet traits are often species-specific, they are commonly used in the taxonomy and phylogeny of grasses.