A Close-up View of a Bougainvillea Hybrid
View of a Bougainvillea Hybrid
by Brian Johnston (Canada)
Bougainvillea’s spectacular floral
display is admired throughout the world. Native to tropical South
America, Latin America, the Caribbean, and Southeast Asia, it can grow
in a small pot, be a sizable tree, or spread like a vine over a
wall. In cooler climates it grows happily as a house plant, or
hanging basket. It certainly is versatile!
Bougainvillea was discovered in the
1760’s in Rio de Janeiro by a French naturalist named Dr. Philibert
Commercon. He named it after his friend Louis-Antoine de
Bougainville, a ship’s admiral and the captain of the vessel that
carried him around the world in a voyage during the period 1766 to
1769. In the early 19th century Kew Gardens in England
played an important role in disseminating Bougainvilleas that it had
propagated to British colonies throughout the world.
The particular hybrid studied in
this article, Bougainvillea glabra
‘Vera’, has brilliant red blooms and a compact habit. It
can be seen in the image above. Additional images follow that
show closer views of the colourful flowers. Well, not
really. Only a couple of the images show Bougainvillea
flowers! The brilliant red structures are not the flowers’ petals
at all, but simply the protective bracts (modified leaves) that
surround and protect the real flowers! The real flowers are the
insignificant tubular, cream-coloured structures visible in a few of
the images. (Another similar situation exists in the Poinsettia
Bougainvillea’s leaves are
evergreen in tropical climates, and semi-deciduous in colder
climates. Leaves can have different shapes depending on the
variety, but here they look remarkably similar to Lilac leaves!
They are glossy green in colour, and it is obvious from the images that
their colour darkens as they mature. Each leaf has a central
longitudinal vein, with branching off-shoots.
The higher magnification
macrophotograph below shows the more random vein pattern between the
off-shoots. The photomicrograph on the right shows glandular
hairs growing from the surface of a vein on the leaf’s under-surface.
A tiny pink leaflet grows from one
of the nodes on a stalk.
Photomicrographs reveal the
cellular structure of the leaflet’s surface.
One of the colourful bracts has a
similar surface which is clearly veined.
A bud-stage inflorescence can be
seen below. Three bracts surround an equal number of flower buds
which have rounded tips.
If one of the bracts is removed, it
becomes possible to see the remaining two flower buds, which look like
waxy tubes with bulbous bases. These bases are the flowers’
ovaries. Notice that the ovaries grow from the central part of
bracts, and not from the ends of the flowers’ stalks.
Longitudinal ridges run the entire
length of the flower buds.
For some unknown reason, a genetic
fault has resulted in the strange malformation seen in the images
Although the vast majority of
gardeners call this plant the Bougainvillea, a common name does
exist. Since the colourful bracts have the look and feel of
paper, the name ‘Paper Flower’ is sometimes used.
Several examples showing the
variation in the size of flower bracts can be seen below. Notice
that very immature flowers have yellowish-green bracts, which
transition to light pink as time passes.
None of the flowers shown in the
three images that follow have bloomed as yet. Blooming is a slow
process that involves both the bending back of the three bracts, and
the opening of the actual flower’s petals.
Usually only one of the flowers
within a group of three bracts opens to begin with. Over a period
of up to a week, the second and third flowers may open. The cream
coloured corolla of the flower has a number of wavy lobes.
Here is an example where two
flowers have bloomed in the flower-head. Within the corolla
tubes, you may be able to see the yellow tips of anthers.
These anthers are more apparent in
the image below.
If part of the corolla tube is
removed, the yellow anthers and their pale green supporting filaments
become visible. Note the variation in the lengths of these
stamens. (You may have noticed that the flower’s pistil is not
visible. It is located at the narrowing which designates where
the corolla tube ends and the ovary begins.)
Here is another group of images
showing the Bougainvillea flower’s stamens.
Photomicrographs showing the
extremely thin connection between an anther and its supporting filament
can be seen below.
On the left below is an image that
shows pollen grains adhering to the anther’s surface. The image
on the right shows that an anther is divided into lobes.
The corolla tube has been removed
in the three images that follow in order to show the flower’s
pistil. A rather large diameter green style supports a white
stigma whose surface is covered by tiny protuberances.
Photomicrographs showing these
protuberances can be seen below. As usual, the protuberances
increase the stigma’s surface area and help it to acquire and retain
If a scalpel is used to remove the
outermost layer of tissue from the corolla tube, and the tissue is
examined under the microscope, the view is as follows.
If a vein on the base of one of the
bracts is examined microscopically, the tiny red hairs that can be seen
below are visible.
It is estimated that there are over
300 varieties of Bougainvillea worldwide, in colours as diverse as
white, pink, orange, purple, burgundy and of course, bright red.
Its unique and graceful form is certainly a super-star in the botanical
The low magnification, (to 1:1),
macro-photographs were taken using a 13 megapixel Canon 5D full frame
DSLR, using a Canon EF 180 mm 1:3.5 L Macro lens.
An 10 megapixel Canon 40D DSLR,
equipped with a specialized high magnification (1x to 5x) Canon macro
lens, the MP-E 65 mm 1:2.8, was used to take the remainder of the
The photomicrographs were taken
using a Leitz SM-Pol microscope (using a dark ground condenser), and
the Coolpix 4500.
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
A complete graphical index of all
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
December 2010 edition of Micscape.
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