Showy, or Pink and White, Lady Slipper Orchid

Botany

Cypripedium Reginae

Lifecycle

Structure

Evolution

Additional Interest

Cypripedium reginae is more commonly known as Pink and White Lady's Slipper, Queens Lady's Slipper or Showy Lady's Slipper (Kartesz, 1994). Coming from the plantae kingdom, it is of the order asparagales, and Orchidaceae, and the subfamily Cypripedioideae, of the genus cypripedium (Kartesz, 1994). This herbaceous perennial flower, which is a terrestrial temperate orchid, is the largest orchid native to North America. The plant may be found across a most of the eastern states in North America, including Atlanta, Arkansas and Tennessee, in the south to North Dakota in the west, and up to Canada where it is found in the eastern areas of Saskatchewan, Manitoba, Ontario, Quebec and Newfoundland (Nature Serve, 2014; Kartesz, 1994). In Minnesota, where it has been the state flow since 1902, it is one of the rarest wild flowers in state (Minnesota Department of Natural Resources, 2014). The numbers have been generally diminishing in the wild, with the plant having already vanished from some areas where it was historically found (Nature Serve, 2014).

The main reason behind the decline has been the decline in suitable habitat. The plant grows in damp conditions where there is a high level of light, and can be fund in damp woods, spruce and tamarack bogs, open fens, wet meadows and prairies (Nature Serve, 2014; Minnesota Department of Natural Resources, 2014). The plant may also be fund at the edges of lakes, in ravines, in limestone quarries, on sandy shorelines and algific talus slopes (Nature Serve, 2014).

In Minnesota, one location where the flower can be fund with some effort is Beckham Lake, located in Isanti County (Minnesota Dept. Of Natural Resources, 2014). The conditions suitable for plant growth have been declining as development takes place and land usage changes, including urban development and water pollution from mineral extraction (Felbaum, 1995). In Minnesota the plant is subject to stage legislative protection since 1925, as it is illegal to pick, uproot, or unearth the plant (Minnesota Dept. Of Natural Resources, 2014). It may be argued that this protection is needed due to the long lifecycle.

2.

Lifecycle

The lifecycle of the species is long, it may take up to 16 years for a plant to grow from a seed and produce their first flowers (Nature Serve, 2014). The plants reproductive process is the typical asexual reproduction of vegetative reproduction, and starts between June and mid July, when the plant is in bloom (Nature Serve, 2014). Although the plants are self compatible, insects are needed to act as pollinators to move the pollen to the stigma (Wilson, 2007). The pollinators are most frequently syphid flies, Magachile bees and beetles (Stoutamire, 1967). The pollinator will usually move beneath the anthers which bear the pollen before being guided past the pistils due to the structure of the flower (Nature Serve, 2014; Wilson, 2007).

The rate of reproduction is constrained by the limited number of flowers found on each stalk; it is usual for each stalk to have between 1 and 2 flowers, but unusual stalks with 3 or 4 flowers may also be found. It has been speculated that one of the reasons for the decline of the plant has been the difficulty in this reproduction due tot he structure of the plant, with Guignard (1887) reporting seeing a butterfly; a non-native European Skipper, become trapped in the labellum effectively preventing pollination by smaller pollinators. This is speculation as there does not appear to have been any robust field trials to test the hypothesis.

The pollinated plant may up to half a million seeds. However, many of these seed, which are as fine as flour, will not find a suitable locations to grow. Unlike other flowering plants, the seed of this flower does not have a seed coat, nor does it have a differentiated embryo or an endosperm. In common with other members of the Orchid family, the seeds will germinate in the presence of certain varieties of fungus that provide the seeds with the nutrients required for growth. The actual method of dispersal appears to be divergent, the waterproof characteristic of the seed suggests water dispersion, the light weight also facilitates wind borne dispersal, or the carriage of the seeds on animals (Wilson, 2007).

Once the seed has geminated it will grow at a very slow rate; no more than a few millimeters, or the length of a pencil point, in its' first year. It can take up to 16 years for the plant to produce flowers and be ready for reproduction to take place. Once established the plants have a long life, believed to be up to 100 years (Nature Serve, 2014). It is also known that the plants may not always flower every year, and can enter a dormancy phase (Wilson, 2007)

When examining reproduction, it is worth noting that some lady slipper may also reproduce by the production of offshoots, becoming separate plants (Wilson, 2007).

3.

Structure

The structure of the reproductive system, with the stamens united with the anthers is shown in figure 1 below. The stamens within a Lady's Slipper are inserted onto the style, known as gynandrous. Unlike other orchids where there is only one perfect stamen, the Lady's slipper will have two good stamens. The image below shows the anthers (a) of the two good stamens. Stig is the stigma. There is also an aborted stamen (st), and the growth that should be another anther has changed into a growth that has a petal like appearances (Gray, 2010). The role of these organs in reproduction has already been explained in section 2.

Figure 1; Stigma, stamens and anthers of Lady's Slipper

(Gray, 2010)

4.

Evolution

The Orchidaeae family is, arguably, the world's single largest plant family. The entire family includes almost 30,000 species, with many of the flowers evolving in different ways, with the plants adapting to their environment, and evolving to meet the needs of pollinators to provide for mutual benefit. The range of diversity is great, with the largest proportion of the family species being found in tropical regions, but a large number of temperate terrestrial orchids have also evolved. In a molecular analysis undertaken with a sample of 56 different orchid genus Cypripedium, Li (et al., 2010) confirmed that this was a monophyletic family. The evolution of the plant can be traced into different evolutionary splits. The first is seen with the split between the Mesoamerican species and the Asian species. Tracing cypripedium reginae, the Mesoamerican split into two lines, and the development continued, with cypripedium reginae emerging from one of these lines. In previous studies morphological characteristics, such as the color of the flowers, was used to assess evolution, but Li (et al., 2010) found results that the evolution was based in distribution, with local adaptations found.