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A flower cluster segregated from any other flowers on the same plant, together with the stems and bracts (reduced leaves) associated with it. Certain plants produce inflorescences, whereas others produce only solitary flowers. See Flower
the flower-bearing part of the annual shoot of a plant. An inflorescence consists of a more or less complexly branched system of axes and flowers that develop in the bracteal axils. The classification of inflorescences is for the most part artificial; they are usually said to be simple or compound, depending on the order of the axes (one or two, two or three, or more) that bear the flowers.
Simple inflorescences include those that are botryose (raceme, corymb, spike, ament, spadix, umbel, capitulum, head) and those that are cymose (simple pleiochasium, dichasium, mono-chasium). Botryose inflorescences are marked by monopodial branching and acropetal opening of flowers; cymose inflorescences, contrastingly, are characterized by sympodial branching and basipetal opening of flowers.
Compound inflorescences are divided into homogeneous, heterogeneous, and mixed inflorescences. In homogeneous compound inflorescences the initial branching and all subsequent branching are the same type (compound raceme, compound umbel, compound spike, compound pleiochasium, compound dichasium, compound monochasium). Heterogeneous compound inflorescences consist of combinations of various types within the botryose (a panicle of spikes, a capitulum of heads) or cymose group (a pleiochasium of dichasia, a dichasium of monochasia). Mixed inflorescences are combinations of botryose and cymose inflorescences (a pleiochasium of heads, a dichasium of racemes, an umbel of monochasia).
In constructing a morphogenetic classification of inflorescences not only shape and structure are taken into account but also the paths of development, principal among which are an increase in the number of lateral shoots, the formation of special inflorescences, the underdevelopment of leaves, the conversion of middle leaves into apical ones, the loss of the apical flower, a change from basipetal to acropetal flowering, and a shortening of lateral and principal axes.
Some botanists consider the compound pleiochasium to be the most primitive inflorescence, that is, the one from which all others developed by means of simplification of branching. Others view the inflorescence as having derived from a solitary terminal flower. The evolution of inflorescences has led to an increase in the total number of flowers on a shoot, a decrease in flower size, and the uniting of flowers into compact groups (anthodia) resembling a single flower with distinct differentiation of functions among certain flowers (larkspur, fig, spurge) and adaptation to special conditions and certain agents of pollination that ensure seed formation. The transition from simple descriptions of external appearance (spikelike, pyramidal) and from the use of indefinite collective types (panicle, thyrse) to the elucidation of structural differences has had great significance in plant systematics, making it possible to judge the directions of evolution of closely related systematic groups and increasing the number of differential characters.
REFERENCESKaden, N. N. “Soplodiia i sotsvetiia.” Vestnik MGU. Seriia fiziko-matematicheskikh i estestvennykh nauk, 1951, no. 6.
Botanika, 7th ed., vol. 1. Edited by L. V. Kudriashov. Moscow, 1966.
Troll, W. Die lnfloreszenzen, vols. 1–2 (part 1). Jena, 1964–69.
N. N. KADEN