Close-up View of a
Lupinus x hybrida
by Brian Johnston (Canada)
Although several lupine wildflower
species are said to grow in southern Ontario where I live, I have not
seen a single one! (I have looked diligently!) Out of sheer
desperation, I was forced to obtain a large pot containing the hybrid
blooms that are shown in this article. The large, showy spikes of
blue flowers are not only extraordinarily beautiful, but also very
large; a mature flower head averages about thirty-five centimetres in
Lupines belong to the important
family of plants known as the “pea
family”, or more correctly the
family Fabaceae. They
are also sometimes referred to as
legumes. Other members of
the family include the beans, soybeans,
peas, peanuts and sweet peas. Many family members are cultivated
as field crops, some are grown as ornamentals, and others occur as wild
plants. Most legumes have nodules on their roots that contain
symbiotic bacteria that convert, (or “fix”), nitrogen from the
atmosphere into forms that are useful to plants. The soil in
which a legume grows is actually improved!
The common name lupine, and the
genus name lupinus derive
from the Latin lupus which
“wolf”. Strangely, it was once believed that lupines decreased,
(or wolfed), the soil’s
fertility. In fact the exact opposite is
now known to be true!
What a remarkable transformation
occurs as the lupine flowerhead in bud stage develops into the final
mature flowerhead seen above. At first, what appear to be pale
green buds are tightly packed in a tapered cylindrical structure.
Then, near the bottom of the
structure, individual, lighter coloured buds can be
distinguished. If you look carefully at the right-hand image, the
bottom-most ring of buds have just a hint of their final purple-blue
A closer look at this developmental
stage reveals the faint hue more clearly. What is also apparent
is that we have been fooled! The lower, pointed, lighter coloured
structures seem to be hairless, while the upper structures are pale
green, and hirsute (hairy). In fact, what appeared earlier to be
buds, are actually the green, hairy leaflets that completely cover the
hairless buds beneath! Several of these leaflets can be seen clasping
the bottom of buds in the left image below.
The following photographs show the
situation more clearly. The lupine buds have “grown out of” their
fixed-size leaflet jackets. Notice in the image at left that the
bottom-most buds have become deeper in colour, and that the stalks
connecting them to the stem have lengthened. The leaflet at the base of each bud
has begun to atrophy, and turn a yellowish-brown colour. Now
visible is a ring of pale green sepals (modified leaves) at the base of
After several days have elapsed,
the bottom-most flowers are in full bloom, having achieved their final
Notice in the unopened buds located
at the middle of the flowerhead, that only a narrow stripe is coloured
blue, and the two “sides” of the bud are white. It also appears
that the open flowers have a purplish-blue colour, while the stripe on
a bud is a truer blue.
The transformation from leaflet
covered bud, to exposed bud, can be seen clearly in the image below.
Newly exposed buds are striking in
the subtlety of their colouration. If you look closely, you can
see the small leaflets that covered the buds at an earlier stage.
Study the three images that follow
to see how the white “sides” of a bud curl back to form the furrowed,
white columnar structure that exists above the coloured lower section
of a blooming flower. (More about a flower’s structure later.)
You may have noticed in earlier
images, that the leaves of the hybrid lupine are divided into (usually)
twelve leaflets. These leaflets are arranged in a fan shape that
is sometimes referred to as digitate
(like the fingers on a
hand). At first all of the leaflets are packed together, and they
slowly separate over a period of time. The image below shows this
process at an early stage.
Once the leaflets have fanned out
into their final positions, there is one more development that must
occur. The leaflets have been folded in half lengthwise, and they
Here is the centre of a leaf viewed
up-close after this process is complete.
Finally, the leaves are revealed in
all their radial glory!
When the underside of a leaflet is
examined under the microscope, oval structures called stoma and guard
cells are revealed. These control the entry of gases into,
out of, the leaf. The image on the right also shows the hairs
that grow from the leaflet’s underside.
Hairs growing out from a prominent
vein on the underside of a leaflet can be seen in the higher
magnification photomicrographs that follow.
A single lupine flower is shown
below. The stalk ends in several hairy, greenish-brown sepals
that enclose the flower’s base. The topmost white structure is
called the banner.
Beneath the banner are two veined blue
wings. In the image, you
can see only the one closest to the
camera. A second identical wing is located behind the
first. Inside the envelope formed by the two wings is the keel of
the flower. The entire structure is said to have bilateral
symmetry because the left and right sides are mirror images of
The higher magnification image
below shows the sepals more clearly.
Here is one of the wings.
Using the microscope, the cellular
structure of a wing becomes visible. Notice the multi-coloured
pigments that reside in the wing’s cells.
Strange pale violet bands seem to
bridge the gap between the darker blue stripes.
Higher magnification reveals these
bands, and also the cells making up one of the stripes.
If the two wings of a flower are
removed, the keel becomes visible. The flower’s reproductive
structures are contained within this keel. (Remember that the
structure above the keel is the banner.)
When the keel is removed, the
bright yellow anthers (male
pollen producing structures) and their
white, supporting filaments
can be seen. Also visible is the
single, very fine, threadlike style
that supports at its end, the
stigma (female pollen accepting
Look carefully at the third image
below. Five of a flower’s ten anthers are larger than the
others. The pollen produced by these oversized anthers is shed
into the keel, and forms a pollen mass.
This mass is forced up
through a pore at the tip of the keel, and onto the lower body of a bee
as it lands on the flower.
Photomicrographs of an anther and
its filament can be seen below. The flower’s pollen is bright
yellow, and has an ellipsoidal shape.
Higher magnification reveals more
Still higher magnification, using
phase-contrast illumination, gives the best view of individual pollen
The pistil, comprised of the thin
supporting style, and “frayed” looking stigma, can be seen in the image
at left below. The stigma itself can be seen in the higher
magnification photomicrograph at right.
The stigma is so small that it is
difficult to get sufficient depth of field to allow the entire
structure to appear in focus. The image on the left shows the
hair-like protuberances that help collect and retain pollen grains,
while the one on the right shows the pollen grains themselves.
About one week is required for the
transformation from the bud-flowerhead, seen on the left below, to the
(almost) fully blooming one, on the right.
Although the bud stage is a very
compact form, the constantly lengthening flower stalks make the
blooming stage very large by comparison. The flowerhead’s base is
typically about 12 centimetres in diameter.
This hybrid lupine produces
flowerheads with extraordinary structure and colouration!
When viewed up-close, one
additional detail can be seen. In the image on the right, the
bottom of the white banner has a group of red spots just above the wing
section. I wonder whether this is an evolutionary development to
help attract bees to exactly the right spot?
The final image shows that near the
end of a flowerhead’s blooming period, the flower stalks have grown so
long that the bloom appears slightly straggly. In my view,
earlier stages are more photogenic.
Approximately 200 lupine species
are known worldwide. They have many admirers, including
butterflies, bees, hummingbirds, and this macro-photographer!
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
The photomicrographs were taken
with a Leitz SM-Pol microscope (using dark ground and phase contrast
condensers), and the Coolpix 4500.
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)
- Little, Elbert L. National
Audubon Society Field Guide to North American Trees - Eastern Region.
2004. 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 April
2008 edition of Micscape.
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