A Close-up View of the Gerbera Daisy

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 central region.

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 the bloom.

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 follows.

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 particularly colourful.

The pinkish-orange bloom below has a group of rogue, randomly sized florets at the outer edge of the trans section.

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 outer edge.

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 three-dimensionally veined.

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 dispersal).

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 stamens follow.

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!

Photographic Equipment

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.

Further Information

The Gerbera Association

http://www.gerbera.org/

Structure of gerbera inflorescence and flowers

http://honeybee.helsinki.fi/mmsbl/gerberalab/gerbera_structure.html

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