A Close-up View of a Lady's Slipper Orchid hybrid


 

A Close-up View of a

Lady's Slipper Orchid


Paphiopedilum maudiae Hybrid (C)


by Brian Johnston   (Canada)



This article focuses on still another hybrid Lady’s Slipper orchid, this one with a restricted colour pallet consisting of white and shades of green. An earlier article that can be found here  looked at more colourful Paphiopedilum hybrids.

Most orchids of this genus are terrestrial, meaning that they grow in well drained ground locations, rather than clinging to trees (epiphytes), or rocks (lithophytes).

All Lady’s Slipper orchids belong to the Cypripedioideae, a sub-family of the Orchidaceae.  They differ from the rest of the orchids in that they possess two anthers instead of the usual one.  Although in many orchids, one petal forms a landing platform for insects, here it is transformed into an elegant, and very distinctive pouch-shaped insect trap.

The Paphiopedilum genus was established by Ernst Hugo Heinrich Pfitzer in 1886.  Generated using  Paphia, one of the surnames of Aphrodite, and pedilon meaning a sandal, the genus translates to “Aphrodite’s sandal”.  This is in reference to the bulbous pouch which is the orchid’s trademark characteristic.

As you can see from the photograph below, this orchid’s stem was not strong enough to support the mass of the flower, and required assistance.



The stem has a round cross-section, and is completely covered with very fine hairs.



Orchids normally have an outer whorl composed of three sepals (modified leaves that protect the flower’s bud stage), and an inner whorl of three petals.  Paphiopedilums however, are different.  The distinctive banner-like structure at the top of the flower is the dorsal sepal.  The other two sepals are smaller, and are fused together to form an apron-shaped structure that is hidden behind the pouch at the flower’s base. This structure, referred to as the synsepal, hangs down from the point where the flower’s stem-like ovary meets the bloom.  Notice that like the dorsal sepal, it too is white with green stripes.  Two of the flower’s three petals can be seen as the striped green wings that angle down from the flower’s centre.  The third petal is grotesquely transformed into the flower’s distinctive pale green pouch.  This unusual structure is called the labellum or lip.



A closer view of one of the petals reveals the randomly spaced bumps that grow along its edges.  The rotated image of the central area of a petal shows its raised ridges, and cellular detail.



Additional rotated images show magnified views of these bumps, and the many almost transparent hairs that grow along a petal’s edges.



In this hybrid, although the entire dorsal sepal angles forward, its tip curves in the reverse direction.  The sepal itself is composed of translucent cells, and is quite different in substance from that of the petals, which tend to be more leathery.  The light green “veins” or “ribs” are raised a considerable distance above the white tissue of the rest of the sepal.



By adjusting the lighting angle, the three-dimensionality of the raised ribs is accentuated.



Here the magnification has increased to the point where individual cells can be seen.



Two images follow that show a reverse view of the base of the dorsal sepal.  The image on the left shows that a very short stalk connects the flower to the slightly larger diameter ridged ovary.



Before we look at the reproductive strategy of the Paphiopedilum orchid, a little terminology must be understood.  Both the flower’s male, and female reproductive organs are held at the end of a rod-like structure called the column (or gynostemium), which is an extension of the stem and ovary.  Two fertile anthers are attached to the column, one on either side.  A curiously modified third anther, this one infertile, is located at the end of the column.  Looking somewhat like a shield, it is called the staminode.  Also connected to the column, but hidden behind the staminode, is the flower’s stigma.  The relative positions of all of these reproductive structures can be seen in the diagram and image that follow.





Since the anthers and stigma are hidden behind the staminode, a visiting insect cannot see them.  In other orchid species, the labellum provides a landing place in close proximity to the reproductive parts - not here however.  While searching for nectar, an insect may fall into the Paphiopedilum’s pouch, and be caught in the trap.  Unfortunately for the insect, the inside of the pouch is lined with shiny, slippery cells – except in one location!  On the interior dorsal wall (the back of the pouch), there exists a ladder made up of tiny hairs that point upwards.  Only here can the insect escape in the same way a wall climber does, by using the projections that are provided for that purpose.  When the insect reaches the top of the labellum, it is very conveniently positioned immediately below one or other of the anthers, and the stigma.  Notice in the two images that follow, how the sides at the back of the labellum curve inwards to produce a vertical tunnel that funnels the climbing insect into the correct position.  The shield-like staminode is outside of the tunnel, but the stigma (pale greenish-white disk) is within the tube formed by the back of the labellum.



If the labellum is removed from the flower, it becomes easier to see the disk-like stigma.  Note that the stigma’s receptive surface faces down, and is not visible in the images.  The staminode is certainly artistically shaped!



The strange nose-like protuberance at the bottom of the staminode, and the many fine hairs that cover the staminode’s surface, can be seen in the higher magnification images below.



Notice in the image on the left below, how effectively the curved back surfaces of the labellum funnel an insect up towards the flower’s two anthers.  The magnified view of the labellum’s surface on the right shows its subtle veining, and shiny surface texture.



In the higher magnification images of the orchid’s anthers that we will see later, it is not obvious that the anthers are bi-lobed.  This fact can be seen clearly however in the right-hand image below.



Each anther is attached to the column by a small horn or “hanger”.  In Paphiopedilums, the pollen is held in a waxy, fairly undefined mass with the consistency of mealy beeswax.  In the images below, this mass of pollen is pale yellow, and a section of a sphere in shape.  The light brown material attached to the outermost region of the pollen mass, is called the anther cap.  Between the anther cap and the pollen mass there is a bright red layer.  The sticky, waxy cap is what gets stuck to the leg or body of an insect as it brushes against the structure.  As the insect moves away, it carries the cap, and the attached pollen mass with it – perhaps to the stigma of this flower, or perhaps to the stigma of a nearby flower of the same species.  Self-fertilization would be the result of the first possibility, and cross-fertilization the result of the second.  Of course, cross-fertilization is preferred for the long-term well-being of the species.  (In both images, the staminode is in the upper right corner, while the stigma, which faces down, is at the bottom.)



The two views that follow show a hanger, and its attached pollen mass.



When photographed from an unusual angle, the receptive surface of  the orchid’s stigma becomes visible.



Notice that the base of the hybrid’s ovary is cupped by a leaflet.  It’s the bottom of this leaflet that marks the end of the plant’s stem, and the beginning of the ovary.



The flower’s ovary is pale green, with raised, deeper green, longitudinal ridges.  Its surface is densely hairy.



Many, but not all Paphiopedilum orchids have mottled, or patterned leaves.  The one shown below belongs to the Lady’s Slipper Orchid studied in this article.



Details of the mottled pattern, and the leaf’s microscopically bumpy surface texture can be seen in the high magnification images below.



The Chinese and Japanese cultures began writing about orchids a couple of thousand years ago.  Over the last few centuries, these unique flowers were actively cultivated, at first by gardeners of the wealthy aristocracy, and later by growers interested in monetary gain.  It’s believed that there may be more than 35 000 orchid species, and in addition, many hybrid varieties like the one shown in this article.


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.

An 8 megapixel Canon 20D 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.



 All comments to the author Brian Johnston are welcomed.

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