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Bifrenaria, abbreviated Bif. in horticultural trade, is a genus of
plant in family Orchidaceae. It contains 20 species found in Panama,
Trinidad and South America. There are no known uses for them, but
their abundant, and at first glance artificial, flowers, make them
favorites of orchid growers.
The genus can be split in two clearly distinct groups: one of
highly robust plants with large flowers, that encompass the first
species to be classified under the genus Bifrenaria; other of more
delicate plants with smaller flowers occasionally classified as
Stenocoryne or Adipe. There are two additional species that are
normally classified as Bifrenaria, but which molecular analysis
indicate to belong to different orchid groups entirely. One is
Bifrenaria grandis which is endemic to Bolívia and which is now
placed in Lacaena,[2] and Bifrenaria steyermarkii, an inhabitant of
the northern Amazon Forest, which does not have an alternative
classification.
Description
Bifrenaria tyrianthina showing the prominent banana-like pseudobulbs
of larger species.
By contrast, the pseudobulbs of smaller species, such as this
Bifrenaria racemosa, a much less noticeable.
Bifrenaria are generally robust plants, of sympodial growth,
between ten and sixty centimeters tall. They are characterized by
round-section root with thick velamen, four-angled fleshy
pseudobulbs of one internode, often basally protected by dried
sheaths and with only one apical leaf(except for Bifrenaria
steyermarkii, which occasionally has two), plicate (fan-folded)
enervated leathery leaves, yet malleable and not exceedingly thick,
with a pseudo-petiole of basal round section, and a basal
inflorescences bearing up to ten flowers, which seldom surpass the
leaves' length.
Bifrenaria flowers are strongly scented, they have sepals
slightly larger than the petals, with the lateral ones basally
united to the column foot forming a calcar with truncated
extremity.The column is slightly arching, generally without wings or
any other appendages, bearing a foot which the labellum is hinged
to, whose shape varies, articulated to the column, with a
longitudinal channeled callus often with a basal claw. Flowers show
two elongated stipes, hardy ever one, at least twice longer than
wide, with salient viscidium, visible caudicles and retinacle in
inverted positions. The superposed pollinia number four, and are
protected by a deciduous incumbent anther. Fruits are green, erect
or pendulous; they take about eight months to ripe and hold hundreds
of thousand yellowish or brownish elongated seeds up to 0.35 mm
long.[7] Among all the mentioned, the main characteristic
distinguishing Bifrenaria from its closest relatives is the presence
of the calcar. Other important characters are the four-sided
single-leaved pseudobulbs besides the raceme inflorescence with two
to ten flowers.
Little is known about pollination in Bifrenaria. Apparently the
only existing records report the presence of some large species'
pollinia observed on the back of male Eufriesea violacea bees (Euglossinae),
and of Bombus brasiliensis (Bombini). Although there are no reports
of flower pollination being directly observed, a paper published in
2006 studied the micromorphology of the labellum in Bifrenaria
species, looking for substances useful to insects as food. The
absence of such substances on the densely pubescent surface of most
Bifrenaria labelli seems to indicate possible pollination by large
bees as the major mean. Another indicator of this possibility is the
strong smell emanated by species like B. tetragona which are similar
to those of plants in other families which are also pollinated by
these bees. The smaller pubescent species may be pollinated by
smaller bees, while the smooth ones, which have strong colored
flowers, as B. aureofulva, might be pollinated by hummingbirds. |
