Close-up View of the
by Brian Johnston (Canada)
The gerbera daisy must be one of the
most popular flowers based upon its numbers in florist shops and other
retail outlets. All year long, both cut flowers and potted plants
are readily available in a surprising number of locations. Little
known even twenty years ago, the colourful flowering plant has
obviously become fashionable. Several hundred varieties of
gerbera, including hybrids, have been documented, with almost any
colour available - except blue. It is not only colour variations
that exist; plants have been developed with serrated or frilly petals,
very wide petals, and double flowers.
In this article, I hope to show a
variety of these hybrids simply as “eye candy”. As usual however,
there will also be some botanical information for interested readers.
Gerberas were named after Traugott
Gerber, a German doctor. The plant is native to South Africa
(Transvaal and Cape Province), and this accounts for the alternative
names Transvaal daisy and African daisy. Over time the plant has
migrated to Madagascar, tropical Asia, and South America.
Gerberas belong to the Aster family (Asteraceae) and possess composite flowers with both ray and disk florets.
The central flower in the article’s
first image is a particularly unusual one. It has multiple rings
of increasingly large overlapping petals surrounding the central dark
disk. A closer view can be seen below. The second image has
been post-processed in Adobe Photoshop in order to accentuate the contrast in
the florets near the flower’s centre.
Two higher magnification images
follow that show the three flower types that exist in gerbera composite
blooms. The dark central disk contains “disk florets”. Around this disk is a ring
containing intermediate “trans florets”. Finally, the outer petals
constitute a final ring of “ray florets”. In the photographs, the yellow
“banana-like” structures are the male stamens (pollen producing organs) of the trans
and ray florets. If you look carefully, it is possible to see
what appear to be three petals associated with each trans floret.
The broad petal (on the side of the flower’s outer radius) is actually
made up of three fused petals - two “lateral” petals on either side
of a “ventral” petal. The three petals cannot be distinguished
individually. The two remaining petals (called “dorsal” petals),
appear to be separate and face the central disk of the flower.
The florets therefore have five petals, of which only three are visible.
Three less complex gerbera blooms
can be seen below. Here, the multiple rings of outer petals are
composed of ray florets with nearly the same size. Notice in the
reverse view, the difference in colour between the fronts and backs of
the ray florets.
A closer look at one of the blooms
shows the three regions discussed earlier. Here however, the
central disk florets are lighter in colour, and easier to see.
This central region also contains male stamens.
Another similar flower has a larger
The striking bloom below is closer
in structure to the cream coloured one seen earlier, but the trans
florets here have smaller petals. In the reverse view, notice the
very hairy green sepals (modified leaves) that ring the base of
A much higher magnification reveals
that the hairs on the sepals are matted, and extremely fine.
Two photomicrographs showing the
tip of a sepal can be seen below. The hairs that cover the
surface appear almost transparent. The second, higher
magnification image shows the hairs to twist along their length.
Two ellipsoidal pollen grains can
be seen clinging to one of the hairs in the photomicrograph that
Higher magnification of the centre
of this flower shows the dense packing of trans florets. In the
second image, a number of stamens can be seen poking out from between
the curled florets.
In the two-coloured bloom that
follows, the trans florets, and associated reproductive structures, are
The pinkish-orange bloom below has
a group of rogue, randomly sized florets at the outer edge of the trans
I prefer photographs with a black
background (provided by black velvet), but for comparison, here is an
image with the normal room background. (The pattern on the
distant wall is discernable because a high aperture number (f 16) was
used to obtain maximum depth of field.)
A closer view of the red flower is
shown below. Notice the bright yellow stamens in the central area
of the trans section, and the much finer, two pronged pistils at the
The photomicrograph of a section of
one of the ray florets shows the cellular structure.
To this point in the article, all
photographs are of gerbera cut flowers grown in greenhouses. The
remainder of the images are of gerbera plants which I attempted to grow. (I don’t possess a
“green thumb”!) The back of each leaf is heavily
Notice that although the fronts of
the two flowers have different colours, the backs are almost
identical. The image on the right shows the densely hairy sepals
at the flower’s base.
The colouration of the orange
flower is spectacular when viewed close-up.
This bloom shows the various types
of gerbera florets particularly well. The dark central disk has a
multitude of white domes which are male stamens. Much more
prominent yellow, pollen encrusted stamens can be seen in the trans
ring. If you look particularly closely, you may be able to see
several bi-lobed female stigmas at the outer edge of the trans ring.
A higher magnification makes the
identification of stamens and stigmas much easier.
The strange central white stamens
are surrounded by many purple hairs called pappus bristles, (specialized organs involved in seed
Two photomicrographs of the stigma
and its supporting style can be seen below. Notice the two
V-shaped lobes at the tip of the stigma.
Several views of pollen covered
The photomicrograph of ellipsoidal
gerbera pollen seen below uses phase-contrast illumination.
Notice in the two photomicrographs
of floret “petals” that follow, the long parallel cells that compose
the structure. Several yellow pollen grains can be seen clinging
to the surface in the second image.
At the base of the reproductive
structures there is a ring which demarcates two different parts.
The lower end is composed of cells
like the ones shown on the left. The top section, shown on the
right, is made up of tightly packed pappus bristles.
The barbed nature of the pappus
bristles can be seen below.
Surrounding the base of the pistil
and stamen, there are tiny brown petal-like ribbons.
A higher magnification reveals (I
think), a number of pollen grains trapped between the brown petals and
the style, or filament.
The diversity of colour and form in
the hybridized gerbera daisy is amazing. These blooms are modern
horticultural monuments to the science of botany!
One half of the photographs in the
article were taken with an eight megapixel Sony CyberShot DSC-F 828
equipped with achromatic close-up lenses (Canon 250D, Nikon 5T, 6T,
Sony VCL-M3358, and shorter focal length achromat) used singly or in
combination. The lenses screw into the 58 mm filter threads of the
camera lens. (These produce a magnification of from 0.5X to 10X
for a 4x6 inch image.) Still higher magnifications were obtained
by using a macro coupler (which has two male threads) to attach a reversed 50 mm focal length f 1.4 Olympus SLR
lens to the F 828. (The magnification here is about 14X for a 4x6
inch image.) The remainder of the photographs were taken with an
eight megapixel Canon 20D DSLR equipped with a Canon EF 100 mm f 2.8
Macro lens. The photomicrographs were taken with a Leitz SM-Pol
microscope (using a dark ground condenser), and the Coolpix 4500.
of gerbera inflorescence and flowers
Microscopy UK or their contributors.
Published in the March
2007 edition of Micscape.
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