A Close-up View of a Hybrid

"Blanket Flower"

Gaillardia grandiflora 'Fanfare'

by Brian Johnston   (Canada)

Every once in a while, a random genetic variation occurs in a plant.  The term “sport” is used to describe the result.  Seldom does the variation look as spectacular as the one shown above!  Blanket flowers of the wildflower type, (native to the central United States and Canada), are sometimes called Indian blankets or Brown-eyed Susans, and they all tend to look like colourful daisies.  For many years hybrid Blanket flowers have been developed by the horticultural industry, and most share one particular characteristic of the wildflower varieties.  This characteristic has to do with the outer ray flowers of the flowerhead.  In simple terms, the ray flower petals are flat.  In the “sport” Gaillardia grandiflora ‘Fanfare’ however, each outer ray flower petal has a quill, or trumpet shape.  This results in one of the most spectacularly colourful, and structurally interesting flowers that it has been my pleasure to photograph.

Members of the aster family, (Asteraceae), possess a flowerhead consisting of a central disk, containing small disk flowers, and an outer ring, containing larger ray flowers.  The genus Gaillardia to which the particular species photographed for this article belongs, is named after the French botanist Gaillard de Marentoneau.

The image below shows several stages in the flowering process.  In the central region of the image, there are several green buds, with an early-stage blooming flowerhead visible above them.  Notice that the ends of the ‘trumpets’ have not yet flared out in this flowerhead.  A mature flowerhead is shown at the bottom of the image.

At least three rings of green sepals, (modified leaves), completely enclose the early bud-stage flowerhead.

Eventually, the sepals open out to reveal the tiny, light green buds.  At first, (in the image on the left), there is no way to distinguish between disk and ray flower buds.  A little later however, the outer ring of ray flower buds differentiates itself (right image).  Notice the extreme hairiness of the sepals shown in both images.

Over a twenty four hour period, the outer ray flowers have grown in length, and their colours have changed, and intensified.

The next transformation has the ends of the closed ray flower tubes starting to open to their final trumpet shape.

Side views reveal the overall cup-shape of a flowerhead at this stage.

Even before their trumpet shaped ends are fully revealed, ray flowers are strikingly beautiful, with their deep red vein structure, bright yellow tips, and fine hairy coating.

At last, the ray flowers are completely in bloom.  Strangely, the fused petal tubes of ray flowers end in variable numbers of petals – four, five, or unusually, three.  Also note that in the central disk of the flowerhead, an outer ring of disk flowers has begun to bloom.

Below are three additional images showing Gaillardia grandiflora ‘Fanfare’ ray flowers.

If the lower surface of one of the sepals, that can be seen in the image on the left, is examined under the microscope, the stoma and guard cells that control gas transfer into and out of the surface can be seen.

Higher magnification reveals the segmented structure of one of the hairs on the sepal’s surface.  The image at right shows the contents of what I assume to an insect egg.

The four images that follow show the spectacularly colourful structure of Gaillardia grandiflora ‘Fanfare’ ray flowers.

The raised, dark red ‘veins’ on the fused petal section of a ray flower are clearly visible below, as are the fine hairs that cover its surface.

Ray flower petals are deeply furrowed, and their surfaces are rough.

A photomicrograph of the upper surface of a petal can be seen below.  Notice the ‘jig-saw-puzzle’ shape of individual surface cells.

A lower magnification view of a section of the petal near a vein follows.

Veins on the underside of a petal have red hair-like structures growing from them.  These hairs are also present away from veins, but their number decreases as the distance from the vein increases.

Higher magnification shows that these hairs, like those on a sepal, are segmented.  (Several pollen grains can be seen clinging to the petal’s surface in the image on the right.)

Now let’s turn our attention to the central disk of the composite flowerhead, with its smaller disk flowers.

Disk flowers bloom first, along the outer perimeter of the central disk.  The pollen coated structures that project out of the flowers are actually the flower’s pistils.  The pollen generating anthers are hidden from view within the tiny fused tube of the disk flower, and are not visible to an observer.

The strange looking bristly structures that can be seen below, are the unopened buds of disk flowers.  Each of the tiny red hairs emanating from the top of a bud is a “pappus”, (a structure connected to a flower’s seed, used to aid in the transport of the mature seed to a different location, sometimes by wind, or by attaching to an animal bypasser).

Later, the blooming section of the central disk has increased in size, and more red pistils are visible.

Notice that it is mostly the ‘newly erupted’ pistils that are pollen-covered.  Those that have been exposed for some time are almost pollen-free.

The disk flowers shown here have almost completed blooming.  Notice that each red stigma is bi-lobed.

With sufficient magnification, the central disk of Gaillardia grandiflora ‘Fanfare’ appears to be a cluttered, but interesting, location!

Just above the centre of the image below, there can be seen a single disk flower with its petals unopened, but pollen covered.  The anthers mentioned earlier are located just inside these petals.  As the stigma and its supporting style extend out of the top of such a flower, pollen grains become stuck to the hairs along the edges of the stigmas’s two lobes.  Just such a situation can be seen below the centre of the image.  It is just possible to see the opening at the top of the flower through which the stigma extended.

The two photomicrographs that follow show the shape of individual disk flower petals (left), and the spiky edge of the colourless tissue that connects the petals at their bases (right).

Even with the macro-lens stopped down to f16, the depth of field is extremely narrow.  Examples of this phenomenon can be seen in the three images below.  The first two show the tiny projections on the edges of stigma lobes that help capture pollen grains.  The last shows the stigma as it is forced out of the tube formed by the fused disk flower petals.  One might expect self-fertilization to be a problem when the stigma exits from the disk flower coated with the flower’s own pollen.  In fact, it is likely that the stigma doesn’t become receptive until that original pollen has fallen off – something that happens quite quickly.  Then, and only then, can a pollen grain transported to the stigma by an insect, result in fertilization.

On the left below is a photomicrograph showing the point at which the top of the style becomes the bottom of the stigma.  The cellular structure of the style is shown in the image at right.

Copious amounts of bright yellow pollen become trapped by the stigma’s needle-like projections.

A higher magnification reveals the spiked spherical shape of the pollen grains.

Different illumination techniques provide alternative views of the grains.

Gaillardia grandiflora ‘Fanfare’ is a perfect example of the superb results produced by hybridization techniques.  However, here, as in many other human endeavors, chance plays a part.  ‘Fanfare’ is not a hybrid cross of two hybrids.  It is the chance “sport” of the resulting hybrid – something that could not be predicted!  Whatever its origin, ‘Fanfare’ is certainly a stunning flower.

Photographic Equipment

All of the macro-photographs were taken with an eight megapixel Canon 20D DSLR equipped with a Canon EF 100 mm f 2.8 Macro lens which focuses to 1:1.  A Canon 250D achromatic close-up lens was used to obtain higher magnifications in several images.

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

Further Information

Wildflower Gaillardia

Gaillardia grandiflora ‘Fanfare’

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 October 2008 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 .