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


A Close-up View of a

Lady's Slipper Orchid

Paphiopedilum maudiae Hybrid (B)

by Brian Johnston   (Canada)

This article focuses on another hybrid Lady’s Slipper orchid with a more flamboyant structure, but less colourful appearance than the first.

Most Paphiopedilum orchids 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.

Most of the Lady’s Slipper orchids that I have seen possess long thin stems that hold the flower(s) high above the rosette of leaves.  This particular hybrid, for whatever reason, had such short stems that the flowers nestled amongst the leaves.  Both the white dorsal sepal, and the two yellowish green petals, have subtle structural details that make this hybrid my favourite of the three that I have photographed.

Many Paphiopedilum orchids have mottled, or patterned leaves; however this one has undecorated ones, each bisected by a deep crease.

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.  Two of the three petals can be seen as the wavy-edged wings that angle down from the flower’s centre.  The third petal is grotesquely transformed into the flower’s distinctive pouch.  This deformed, slipper-like third petal is called the labellum or lip of the orchid, and as we will see later, it plays an important part in the fertilization process.

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” composed of tiny upward pointing hairs.  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.  (In the image below, if you look inside the pouch immediately below the staminode, the location of the climbing hairs is apparent.)

The three images that follow show, (with increasing magnification), the upward-angled hairs that aid an insect in its escape from the pouch via the back wall.

Views of a flower’s dorsal sepal show its ornamental shape, and curious spotting.  Although the background colour is white over most of its surface, near the base it changes to light green.

The shield-like staminode that hides the flower’s reproductive structures is shaped like an inverted heart in this hybrid.  The yellowy-orange, nose-like protuberance near its centre gives the staminode a vaguely “fried egg” appearance.

Except near its “nose”, the staminode is coated with fine, purple hairs.  These hairs increase in density near its connection to the column.  In both images, the flower’s white stigma peeks out from under the staminode’s bottom edge.

The column holding the flower’s reproductive structures can be seen in the two views that follow.  Near the base of the column, the hairs are much longer, and have a greater diameter.  In both images, one of the bloom’s two anthers is visible just to the right of the staminode.

The image below shows the relative positions of the male and female reproductive organs in the Lady’s Slipper orchid.  Each anther is attached to the column by a small horn or “hanger”.  Immediately below the anthers is the disk-shaped, white stigma with its active surface facing down, away from the anthers.

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 yellowish-white with a bright red outer layer.  The shiny brownish-yellow material attached to the outermost region of the pollen mass, is called the anther cap.  This 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 this hybrid, each anther is bi-lobed.  The second image shows why it is so easy for the anther to be carried away by an insect that comes into contact with the anther cap.  The point of connection of the anther to its “hanger” appears relatively weak.

As an insect climbs out of the labellum “trap” it “sees” the bottom (active) surface of the flower’s stigma.

Orchids can be found growing on all of Earth’s continents, except Antarctica.  Over the approximately 80 million years that they have existed, their flowers have evolved to attract, deceive, and manipulate insects in order to maximize the possibility of fertilization.  Lady’s Slipper orchids are perfect examples of one such strategy.

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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