Tribe Triphoreae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 87

Fig. 4.1 Triphora trianthophora . ( a ) Flower, front view; ( b ) flower, side view; ( c ) lip, flattened;
( d ) column, ventral view with raised anther; ( e ) column, side view, scale bars = 2 mm. an anther,
po pollinia, sg stigma
produces a faint odor variously described as both sweet and somewhat musty-fetid
(Medley 1979 ). Small droplets of what Medley ( 1979 ) presumed to be nectar are
present at the base of the lateral sepals and labellum.
Flowering of all plants in a particular area is largely synchronous, and the flowers
often open in mid-morning and close by late afternoon on only 1 or occasionally 2-4
successive days (Lownes 1920 ; Medley 1979, 2002 ). According to Keenan ( 1986 ),
flowers more than 1 day old are no longer in prime condition. Successive intervals of
bud maturation and episodes of synchronous blooming may be repeated at intervals of
several days from three to seven times in a single season and the synchrony may
extend over a wide geographic area (Medley 1979 ; Keenan 1986, 1992 ). Each plant
often produces from one to six buds (Table 4.1 ), but usually only one or two, occa-
sionally three, flowers are open at the same time (Keenan 1986, 1992 ; Willems 1994 ).
Blooming may be associated with late summer rains and frequently, but not always,
occurs about 48 h after a drop in nighttime temperature. It is restricted to an interval
from summer to late fall when relatively few sympatric flowers are in bloom, a cir-
cumstance that may reduce competition for pollinators (Sheviak 1974 ; Brackley 1981 ;
Keenan 1986, 1988 ; Medley 2002 ). Extended periods of underground dormancy are