New Zealand Journal of Botany
abstracts
Limiting factors of
reproductive success in Bromus
auleticus (Poaceae). 1.
Flowering phenology, sexual expression, and pollen production
Hugo
F. Gutiérrez
Cátedra de
Botánica Sistemática Agronómica
Facultad de Ciencias Agrarias
Universidad Nacional del Litoral (UNL)
Luis Kreder 2805
(3080) Esperanza, provincia de Santa Fe, Argentina
hgutierr@fca.unl.edu.ar
Diego Medan
Cátedra de
Botánica Agrícola
Facultad de Agronomía UBA
Av. San Martín 4453
(1417) Buenos Aires, Argentina
José
F. Pensiero
Cátedra de
Botánica Sistemática Agronómica
Facultad de Ciencias Agrarias
Universidad Nacional del Litoral (UNL)
Luis Kreder 2805
(3080) Esperanza, provincia de Santa Fe, Argentina
Abstract The
reproductive biology of Bromus
auleticus was studied in three
populations to identify factors related to flowering phenology and
pollen production that could explain low fruit set. Flowering phenology
was examined at the levels of population, plant, inflorescence,
spikelet, and floret. Only one flowering event per year was recorded.
Flowering proceeded downwards in the inflorescence and upwards within a
single spikelet. Spikelets had on average 7.5 ± 1
chasmogamic, hermaphrodite florets and an apical, sterile or staminate
floret. Each floret was open for 3 hours; pollen was shed over
10–75 minutes but the stigma remained receptive for
15–30 hours. There was ample overlap in flowering time among
spikelets of the same inflorescence and among individuals of the same
population; thus, both geitonogamy and cross-pollination were possible.
Hence, the limited female reproductive success of this species cannot
be explained by its flowering phenology, as no mechanism exists (in
space or time) that reduces or prevents the possibility of
self-fertilisation at the levels of the floret, spikelet, and/or
inflorescence, or pollen interchange among individuals of the
population. Neither the amount of pollen per flower or its fertility
rate were limiting factors for adequate caryopsis setting.
Keywords Bromus
auleticus; floral phenology;
floret sexuality; pollen production
B05031; Received 25 July 2005;
accepted 6 January 2006; Online publication date 2 March 2006
New Zealand Journal of Botany,
2006, Vol. 44: 47–55
0028–825X/06/4401–0047 © The Royal Society of New Zealand 2006
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