A Close-up View of a Bougainvillea Hybrid


 

A Close-up View of a Bougainvillea Hybrid


Bougainvillea glabra 'Vera'


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 plant.)





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 below. 





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.



I

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 pollen grains.



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 world.


Photographic Equipment

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 images.

The photomicrographs were taken using a Leitz SM-Pol microscope (using a dark ground condenser), and the Coolpix 4500.


A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.


The Colourful World of Chemical Crystals

A complete graphical index of all of my crystal articles can be found here.


 All comments to the author Brian Johnston are welcomed.

Microscopy UK Front Page
Micscape Magazine
Article Library


© Microscopy UK or their contributors.

Published in the December 2010 edition of Micscape.
Please report any Web problems or offer general comments to the Micscape Editor.
Micscape is the on-line monthly magazine of the Microscopy UK web
site at Microscopy-UK  


© Onview.net Ltd, Microscopy-UK, and all contributors 1995 onwards. All rights reserved. Main site is at www.microscopy-uk.org.uk with full mirror at www.microscopy-uk.net .