Close up view of a bleeding heart cultivar


A Close-up View of a

Bleeding Heart Cultivar

Dicentra spectabilis 'Burning Heart'

by Brian Johnston   (Canada)

Bleeding Hearts are shade garden and woodland plants that have a variety of alternative names such as Dutchman’s Breeches, Dutchman’s Trousers, Venus’s Car, and Lyre Flower.  The cultivar studied here, ‘Burning Heart’, is a recent introduction which forms 30 centimetre high mounds of fern-like foliage and deep red flowers.

It should be kept in mind that members of the Dicentra genus contain a toxic cocktail of poisonous compounds such as isoquinoline-like alkaloids.  Aporphine, protoberberine, and more than 20 compounds structurally related to poppy alkaloids have been found in various Dicentra species.

As can be seen in the first image in the article, and the two that follow, the flowers in a raceme hang from their stalks (are pendulous), and are shaped like hearts with downward pointing protuberances which are thought to represent drops of blood.  (This accounts for the ‘bleeding’ part of the common name.)

Unlike the plant’s mature flowers, its early stage buds are held upright by their short stalks and the stem holding the raceme.  (A raceme is a group of flowers emanating from a single stalk in which each individual flower has its own stalk.)  Only hints of their final colour can be discerned in photographs taken at this point.

As the buds increase in size, their red colouration extends farther, and the stem holding the raceme begins to droop.  Notice that the heart-shaped portion of the bud develops more slowly than the blood-drop protrusion.

My local Garden Centre certainly gave me ‘value added’ along with this Bleeding Heart plant.  When I got it home, I was surprised to find that it was crawling (literally) with tiny green aphids.  They played hide-and-seek with me as I took the first day’s photographs.  I would position the container so that no aphids were in view, and the moment I grabbed hold of the remote shutter release, they would spring into view.  That evening I took special delight in killing all of them by spraying the plant liberally with ‘Raid’.  The paper towels on which the plant was placed were covered with dozens of the little pests’ bodies.  Good riddance!

If a section of one of the flower’s petals is examined under the microscope, its cellular structure becomes visible.  (In order to increase contrast, I utilized Photoshop’s ‘Levels’ function.  This results in the images being false-colour.

A much higher magnification photomicrograph of a section of one of the flower’s curved ‘wings’ shows a cellular structure reminiscent of a stained glass window.

Dicentra flowers have a rather unusual structure.  There are 4 petals, two outer that form the ‘heart’, and two inner that form the projecting ‘blood-drop’ projection.  The outer petals are fused at the base forming what are referred to as two basal sacs, and free at the backward curving ends.  The inner petals are slender at the base, and protrude out through the basal sac structure.  These long petals are fused, forming a crested hood that encloses the flower’s stamens and pistil.

The three images that follow show the curved tip of one of the outer petals.  Notice that the revealed ‘inner’ surface is colourless around the edge and deep purple at its centre.  The first image also shows the crested hood that covers the flower’s reproductive structures.  (The remains of one of the aphids killed by the ‘Raid’ can be seen stuck to the petal’s surface in the last image.)

If both stamens and pistil are covered by this crested hood, how do insects obtain access to them?  The answer can be seen in the image below.  A very narrow longitudinal slit runs the length of the inner petal tube on both sides.  If you look carefully at the top of the slit, you can see evidence of yellow pollen grains on anthers.  Insects with long legs or a proboscis can probe through the slit to obtain or deposit pollen grains in the search for a flower’s nectar.

Removing one of the flower’s inner petals allows one to see the tightly packed reproductive structures.

Six anthers are connected to a tube composed of the six fused, colourless filaments.  The bilobed stigma is positioned at the centre of the ring formed by the yellow, pollen covered anthers.

Higher magnification reveals the tight packing of these structures.

When both inner petals are removed from the flower, over time the anthers separate and give a better view of the bi-lobed stigma.  Since under normal conditions these two petals remain in position, it is not possible for the separation to occur.

After several hours, the sturdy, pale green style which supports the stigma becomes visible.  It appears that several anthers are connected by short filaments to the main filament.

Under the microscope, details of the structure of an anther become clearer.  So many pollen grains cling to each anther that its apparent width is almost doubled.  The last image shows the spherical shape of pollen grains.

The female reproductive structure (stigma) has two prominent horn-like lobes.

Photomicrographs show the red coloured attachment of style to stigma (left) and a more highly magnified view of one of the rounded lobes (right).

Additional photomicrographs show that many pollen grains adhere to the surface of the stigma but surprisingly, not to the horns.  (This stigma appears to be missing one of its projections.)

Still closer views show the cellular structure in the red band between style and stigma.

On the left below can be seen pollen grains clinging to this coloured band.  The image on the right shows the short coloured ‘stripes’ that randomly cover the supporting style.

With all but one of a flower’s petals removed, the position of the ovary at the swollen end of the stigma/style is revealed.

Within the ovary, developing pale green seeds are visible.

Higher magnification reveals the surface texture of a seed (left), and its attachment to the base of the ovary by a thin, dark green strip (right).

Dicentra leaves are so deeply lobed that they are usually described as being fern-like.  Young leaves are yellowish green in colour, while more mature ones are greyish green.

Closer views of the back surface of a leaf show its simple vein structure, and speckled appearance.

A leaf’s upper surface shows no veins.

Veins not visible in the macro-photographs become apparent in a photomicrograph of the lower surface of a leaf.  A higher magnification shows the stomata and their associated guard cells that control gas movement into and out of the leaf’s interior.

Notice in the images below that the cells around the edge of a leaf are colourless, and that the green colour deepens quickly as we look towards its interior.

The cultivar ‘Burning Heart’ is a patented variety with asexual propagation prohibited.  It blooms from mid-spring through to the first frost, and certainly provides colourful eye-candy.

Photographic Equipment

The low magnification, (to 1:1), macro-photographs were taken using a 13 megapixel Canon 5D full frame 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 macro lens, the MP-E 65 mm 1:2.8, was used to take the remainder of the images.

The photomicrographs were taken using a Leitz SM-Pol microscope (using a dark ground condenser), and the Coolpix 4500.

A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.

The Colourful World of Chemical Crystals

A complete graphical index of all of my crystal articles can be found here.

 All comments to the author Brian Johnston are welcomed.

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Published in the December 2012 edition of Micscape.
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