DARWINIANA
34(1-4): 173-182. 1996
ESTUDIOS SOBRE LA VARIACION ESTRUCTURAL DE LAS ESPIGUILLAS EN GENERO
DE LA TRIBU PANICEAE (POACEAE)
ANA M. CIALDELLA1 & ANDREA S. VEGA2
Instituto de Botánica Darwinion, Labardén 200, casilla de
correo 22, (1642) San Isidro, Argentina
ABSTRACT: Cialdella, A. M. & Vega, A. S. 1996. Studies on structural
variations of spikelets in several genera of the tribe Paniceae (Poaceae).
Darwiniana 34: 173-182.
The present treatment deals with different structural variations of
the spikelets in the following genera of the tribe Paniceae (Poaceae):
Anthaenantiopsis Mez ex Pilg., Axonopus P. Beauv.,
Digitaria Haller, Lasiacis (Griseb.) Hitchc., Panicum
L., Paspalum L., Reimarochloa Hitchc. and Urochloa
P. Beauv. This tribe shows a reductive tendency in the development
of the spikelets, mainly in morphological and reproductive characters,
with regards to the number of flowers and bracts of the spikelets (glumes,
lemmas and paleas) and "sexuality" of the flowers. Typical biflowered
spikelets is the most common pattern among the studied genera; three-flowered
spikelets are always present in Panicum quadriglume (Döll) Hitchc.
and Lasiacis anomala Hitchc., being occasional in Anthaenantiopsis
fiebrigii Parodi, A. perforata (Nees) Parodi var. perforata,
Panicum crateriferum Sohns and P. grumosum Nees. Extension
of the rachilla above the upper anthoecium is common in biflowered spikelets
of Lasiacis and Urochloa, being exceptional in Panicum
and Anthaenantiopsis. This study also concludes that there is variation
in the "sexuality" of the flowers in the spikelets: the lower
flower may be perfect, staminate or neutral, while the upper one is always
perfect in the biflowered ones. In the three-flowered spikelets, the lower
flower may be staminate or neutral, the medium one perfect, staminate or
neutral, while the upper flower is always perfect. The occurrence of the
extension of the rachilla is considered as a possible vestigial character,
which represents the transition from many-flowered to few-flowered spikelets.
1 Miembro de la Carrera del Investigador Científico
y Tecnológico del CONICET.
2 Becaria de Perfeccionamiento del CONICET.