Close-up View of the Wildflower
by Brian Johnston (Canada)
cinquefoil, also referred to as rough-fruited cinquefoil, is native to
the Eastern Mediterranean area, and is a member of the rose family (Rosaceae). The first
documented appearance in North America occurred in the early 1900’s in
Ontario, Canada (where I live). By the late 1930’s the species
had spread throughout the northwestern United States. Today, the
invasive nature of this beautiful wildflower makes it very undesirable
both economically, and ecologically. It is therefore often
referred to as a “noxious weed”.
I have chosen in the image above to
show the flower as it often appears - without petals. Sulphur
cinquefoil loses its petals soon after blooming. The slightest
disturbance, usually from the wind or handling, causes the petals to
fall. Since all of my macro-photographs are taken indoors, this
presents a real problem. In the end, the only solution was to
bring back a larger number of plants than was necessary, and hope that
at least a couple of stems would retain their flowers. (The plant
is easy to remove from the ground, as it possesses a single short
taproot with many shallow spreading rootlets.)
A typical plant with a complete
flower can be seen below. The stem supports many leaves along its
length, with the buds and blossoms concentrated at the top.
The leaves are palmately compound,
with 5 or 7 toothed leaflets making up each leaf. Leaves have
hairs on their surfaces and edges. The leaf stem is also
The pale yellow 2.5 centimetre
diameter blooms of the plant contain 5 deeply notched heart-shaped
petals. The “sulphur” in the common name refers to the petals’
light yellow colour. The name “cinquefoil”, of French derivation,
refers to the five-parted leaves. (The genus name Potentilla
derives from the Latin potens
meaning “powerful”, and refers to the medicinal qualities attributed to
the plant historically. Recta, the
species name, refers to the upright orientation of the stem.)
When the bud first forms, the five
long bracts (modified leaves)
that surround it are parallel to its sides.
Later, these bracts open out to
reveal five shorter, wider sepals
(modified leaves). As the flower begins to bloom, these sepals
open to reveal the coloured petals. Notice that all stems,
bracts, and sepals are covered by long, fine hairs.
Eventually, the petals open enough
to reveal the darker yellow reproductive structures within the flower.
Three images follow that
show a sulphur cinquefoil plant in full bloom. It is difficult to
imagine how so beautiful a plant could be referred to as a noxious weed!
A close-up of a flower’s centre
reveals the many stamens with
flat, elongated, disk-shaped anthers
(male pollen producing organs), and slender supporting filaments. Within the ring of
stamens is a dome-shaped mound formed by many pistils composed of stigmas (female pollen accepting
organs), and supporting styles.
Under the microscope, one can see
the basic structure of a stamen. The pollen grains appear to be
concentrated around the outer edge of the anther, and a few can be seen
clinging to the upper portion of the filament.
Higher magnification reveals that
the pollen grains are ellipsoidal in shape.
Still higher magnifications using
dark-ground (left), and phase-contrast (right) illumination show slight
variations in the basic pollen shape.
A pistil with its attached white
ovary can be seen below. The flattened yellow top is the stigma,
while the yellow-green structure supporting it is the style.
(Note that the out-of-focus ovary to the left of the style belongs to
another pistil.) The image at right shows a group of pollen
grains clinging to the ovary’s surface.
Two views follow that show the
rather uneven bumpy surface of the stigma. Note the columnar
cells on the surface of the style in the image at right.
Sulphur cinquefoil plants show
great variation in the colour of the central portion of their
anthers. Notice in the flowers that follow that the central area
is dark brown. If you compare these with the anthers of flowers
shown at the beginning of the article, you can easily see the
remarkable difference. (At first, I thought that the anthers
darkened with age, but this seems not to be the case.)
Once the wind has removed the
petals from a flower, what remains is still quite striking.
Notice the inner ring of sepals, and outer ring of bracts in the images
that follow. In this species, (Potentilla
recta), the flower’s petals are significantly longer than the
sepals and bracts.
In another plant, the central
portions of the anthers are coloured a lighter brown.
If one examines the tip of one of
the green bracts under the microscope, the myriad of fine, almost
transparent hairs can be seen clearly.
The final images show the
flower-heads of a plant about a month after they have completed
blooming. The sepals and bracts are still green, but the anthers
are long gone and the pistils and ovaries have turned a dark red-brown
colour. In the third image the bracts and sepals have been
removed to show the developing fruit which consists of a aggregate of achenes (seeds). The lighter
brown projecting structures are the remnants of the flower’s styles.
The sulphur cinquefoil is a close
relative of the strawberry plant. The flower of the cinquefoil is
larger and more beautiful than that of the strawberry. On the
other hand, the fruit of the strawberry is more appealing, both
visually and gastronomically!
Two thirds of the macro-photographs
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 which focuses to 1:1. The photomicrographs were taken
with a Leitz SM-Pol microscope (using a dark ground condenser), and the
The following references have been
found to be valuable in the identification of wildflowers, and they are
also a good source of information about them.
- Dickinson, Timothy, et al.
2004. The ROM Field Guide to Wildflowers of Ontario. Royal
Ontario Museum & McClelland and Stewart Ltd, Toronto, Canada.
- Thieret, John W. et al.
National Audubon Society Field Guide to North American Wildflowers -
Eastern Region. 2002. Alfred A. Knopf, Inc. (Chanticleer Press,
Inc. New York)
- Kershaw, Linda. 2002. Ontario
Wildflowers. Lone Pine Publishing, Edmonton, Alberta,Canada.
- Royer, France and Dickinson,
Richard. 1999. Weeds of Canada. University of Alberta
Press and Lone Pine Publishing, Edmonton, Alberta, Canada.
- Crockett, Lawrence, J.
2003. A Field Guide to Weeds (Based on Wildly Successful
Plants, 1977) Sterling Publishing Company, Inc. New York,
- Mathews, Schuyler F.
2003. A Field Guide to Wildflowers (Adapted from Field Book
of American Wildflowers, 1902), Sterling Publishing Company, Inc.
New York, NY.
- Barker, Joan.
2004. The Encyclopedia of North American Wildflowers.
Parragon Publishing, Bath, UK.
Microscopy UK or their contributors.
Published in the
February 2007 edition of Micscape.
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