Close-up View of the Coneflower Hybrid 'Pink Double Delight
Coneflower Hybrid 'Pink Double Delight'
by Brian Johnston (Canada)
One look at this striking plant was
enough to convince me that it should be the subject of one of my
Micscape articles. Its spectacularly shaped, and intensely
blooms made nearby plants in the garden centre look positively
The original plant that was
produce this cultivar is the Eastern purple coneflower which is
to the central and south-eastern regions of the United
is a member of the Aster family (Asteraceae),
possesses flower-heads composed of outer ray flowers and inner disk flowers. In
its use as an ornamental, it is popular for its (possible)
The bud stage of the cultivar
Double Delight’ can be seen below. At this early stage
little evidence of the final colouration of the bloom.
A little later however, the
protrusions that will eventually become the flower-head’s ray
have begun to have a faint pink colouration. The central disk,
of disk flowers, has not begun to bloom.
Notice the whorls of curved
bracts (modified leaves) that form the base of the flower-head.
Note in the images that
both the edges of the bracts, and the surface of the
stalk are covered with fine colourless hairs.
The length of the folded or
ray florets increases by millimetres per day as the flower-head
A view from above of a bud
flower-head shows the ring of lengthening ray flower petals, and
look like the tips of immature disk flower buds. In fact,
central structures are not buds at all!
Side views of a bud stage
flower-head, which has been cut longitudinally in order to view
internal structures, can be seen below. In the images, the
shorter, pale green structures with grooved tips are the
flowers, while the longer, darker green structures with reddish
are referred to as ‘receptacle chaff’. These rod-like
surround the many disk flower buds, and in this genus, are the
length or longer than the buds. The genus name Echinacea derives from the
Greek echinos (hedgehog)
and it refers
to this array of spike-like structures growing from the
base (or receptacle).
As usual, looking at the bud
of this plant provides few clues to the simply magnificent
inflorescence that it will transform into. Notice that in
cultivar, the ratio of ray flowers to disk flowers has a very
value. The flower-head blooms from the outside in.
Views from the back of an
inflorescence show the whorls of bracts that ‘cup’ its base (or
receptacle). Notice that near the whorl of bracts, the
increases in diameter and has a group of longitudinal groves on
surface. Also note the very three-dimensional,
veining on the underside of the ray flower petals.
Ray flower petals are flat,
have a variable number of pointed lobes at their tips.
flowers have tubular corollas with a variable number of pointed
along their top edge.
Closer views of the tips of
flowers can be seen below.
A similar view of the tip of a
If one of these petals is
under a microscope, its cellular structure and colouration
easier to see.
Higher magnification reveals
details. Notice that the two images that follow show
same view of a petal. The enhanced contrast in the second
is the result of using Photoshop’s ‘Levels’ function.
this the second image is not true colour.
Photomicrographs (again using
‘Levels’ function) reveal some of the structures on the
underside of a
The outer ray flowers of this
species have very large, relatively flat petals. Disk
however, possess a tubular corolla with pointed lobes around its
edge. The closer the flowers are to the centre of the
smaller they are.
Although the receptacle chaff
mentioned earlier start out longer that the disk flower buds,
blooming disk flowers are tall enough to hide them from
Only in the centre of the disk are they still visible.
Here are several closer views
the interface between bud-stage, and blooming, disk
Remember that the receptacle chaff have bright red tips, while
bud-stage flowers have pale green tips.
Here is a photomicrograph that
shows the tip of a disk flower bud. Its mixture of red and
indicates that it is about to bloom.
If one of the bud’s petals is
removed and examined under the microscope, the colouration of
individual cells becomes visible.
Deep with the corolla tube of
disk flower this strange looking structure exists.
photomicrographs reveal that it is the flower’s pistil. On
surface of the stigma, an array of variable length rod-like
capture and retain pollen grains.
During the period of time that
photographed this plant, the flowers’ pistils did not grow to
length that they were visible to a casual viewer.
The base of the flower-head,
which both ray and disk flowers grow is called the
this species it has a dome shape. One central view showing only
and chaff, and one side view showing blooming disk flowers can
below. Notice that the base of the blooming flowers has a
red colour which abruptly changes to pure white farther down.
Two images show views of an
immature bud with its monochrome colouration, and the third
older bud which is taller, and has a faint pink colouration near
Notice how much taller the
disk flowers are compared to the receptacle chaff.
swelling at the base of the corolla tube is the flower’s ovary.
Additional views of the
the coneflower inflorescence are shown below. Even the
of a flower is attractive when viewed up-close!
The upper surfaces of the
leaves have a small number of prominent longitudinal veins and a
multitude of seemingly random fine veins. Fine hairs grow
over the upper surfaces. Botanists describe the shape of
leaves as broadly lanceolate.
The lower surface of a leaf
fine hairs as well, and its veining is easier to see.
Photomicrographs of the lower
surface reveal these hairs, and in the third image, the stomata
guard cells that control gas entry into and out of the leaf are
Medical benefits of Echinacea have been
many years. It is interesting to note that back in 1852
starter plant of this cultivar, Echinacea
purpurea, was put in the official United States
claiming that it was useful in the treatment of syphilis.
well to remember however that it was also believed to cure
colds, mumps, wounds, burns etc. Need I say more?
The low magnification, (to
macro-photographs were taken using a 13 megapixel Canon 5D full
DSLR, using a Canon EF 180 mm 1:3.5 L Macro lens.
A 10 megapixel Canon 40D DSLR,
equipped with a specialized high magnification (1x to 5x) Canon
lens, the MP-E 65 mm 1:2.8, was used to take the remainder of
The photomicrographs were
using a Leitz SM-Pol microscope (using a dark ground condenser),
the Coolpix 4500.
A Flower Garden of
A complete graphical index of
of my flower articles can be found here.
The Colourful World
A complete graphical index of
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the
February 2013 edition of Micscape.
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