Epillet

Article

October 28, 2021

In botany, the spikelet is the elementary inflorescence characteristic of plants of the Poaceae family (grasses) and the neighboring family of Cyperaceae. The flowers are also grouped in spikelets in neighboring families (also belonging to the order Poales) of Restionaceae, Anarthriaceae, Ecdeiocoleaceae and Centrolepidaceae. It is a small spike, reduced to a few incomplete flowers, called "florets" in the Poaceae, up to ten, rarely more than 40, often two or three, sometimes only one, depending on the species. The spikelets are themselves grouped into compound inflorescences, for example ears (in the case of wheat) or panicles (in the case of oats). In the descriptions in agrostology, a spikelet comprising at least one hermaphrodite floret, leading to the production of a caryopsis, and “sterile” is called “fertile” a spikelet composed only of male (staminate) or asexual florets. Until the end of the 18th century, botanists used the term "locust" (Latin locusta) to designate the "reunion or assemblage of flowers whose number is indeterminate (1 to 20 and more) in a common envelope", replaced by then by the term "épiet", then "épillet" (Latin spicula).

Poaceae (grasses)

Structure of the spikelet

The spikelet is made up of an axis, called the “rachillet”, inserted into the main inflorescence, either by a more or less long peduncle (pedicled spikelet), or often without a peduncle (sessile spikelet). Exceptionally, the axis carrying the spikelet is called "pedicel" rather than peduncle, to distinguish it from the axes of the general inflorescence grouping the various spikelets. On this axis are inserted, in an alternating arrangement, secondary axes which are the floral axes, in variable number. The number of flowers is characteristic of each species. The spikelets are frequently uniflorous (e.g. rat barley) or biflorous (e.g. woolly swell), but they can also have more than ten flowers (sterile brome). There may also be sterile flowers. A spikelet is generally simple, that is, the rachillet is not branched, except in certain genera of bamboo in Southeast Asia in which branched spikelets (pseudo-spikelets) are found.

Glumes

At the base of the spikelet are the glumes, usually two in number, sometimes more. They are two sessile and alternate leafy parts (apparently opposite), elongated and as if folded in half, which cover and protect the base of the spikelet. They are in some cases terminated by an edge. The lower glume is usually smaller than the upper glume, and at times, much reduced, appears absent. These are the equivalent of spikelet bracts.

Glumella

At the base of the floral axes, also sessile, are the lemmas, also two in number, in alternating arrangement. The lower lemma, also called "lemma", is inserted directly on the axis of the spikelet. It is the equivalent of a floral bract. The upper lemma, called the “paleole”, is carried by the secondary axis. The lower lemmas are frequently ridged (awned lemma), usually one, sometimes several. The characteristics of these ridges (length, shape, presence of hairs, mode of insertion) help to determine the different genera and species. The lemmas have the function of protecting the flower, and subsequently the grain (caryopsis). In some cases, these glumes are said to be adherent because they remain attached to the grain at maturity. This is the case with paddy rice, which must be subjected to husking to obtain white rice.

Fleurons

The floral axis, equivalent to the floral peduncle, ends in a single flower, represented

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