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The inflorescences of Paspalum (Poaceae, Paniceae): the Quadrifaria group and the evolutionary pathway towards the fully homogenized, truncated common type

Gabriel H. Rua
Plant Systematics and Evolution
Vol. 201, No. 1/4 (March 1996), pp. 199-209
Published by: Springer
Stable URL: http://www.jstor.org/stable/23642964
Page Count: 11
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The inflorescences of Paspalum (Poaceae, Paniceae): the Quadrifaria group and the evolutionary pathway towards the fully homogenized, truncated common type
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Abstract

The inflorescences of Paspalum are composed of a main axis and 1 to more than 100 raceme-like lateral branches arranged along it. Each branch bears two rows of homogeneous subunits composed either of one or two consecutive-ordered axes, each one ending with a spikelet. In terms of Troll's descriptive and typological system, such lateral branches were regarded as long paracladia which bear homogeneous bi-axial short paracladia. The structural pattern of these long paracladia is considered to be a recapitulation of the distal main-axis structure which was lost by evolutionary truncation. — The occurrence of a main florescence (= terminal spikelet) and a short paracladia-bearing zone at the distal portion of the main axis in several species of the genus Paspalum, as it is exemplified by species belonging to the so-called 'Quadrifaria group', seems to support the hypothesis that the usual inflorescence of Paspalum actually derived from a paniculate structure by evolutionary homogenization and truncation processes. This 'Quadrifariatype inflorescences' would be regarded as an intermediate step in the evolutionary pathway. Nevertheless, the phylogenetic implications of this interpretation remains obscure because at the present time there is not any hypothesis about the phylogeny of the genus available.

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