The family Orchidaceae (or-kid-ACE-e-ay)
What is an orchid?
Terrestrial orchids
Native orchids of NY
Why orchids are unique
Flower structure
Seed production and structure
Mycorrhizae and germination
Flowering time
Sensitivity to the environment
What is an orchid?
Orchids are the largest family of angiosperms, or flowering plants in the world.
Approximately 30,000 species, or 10% of all known species of flowering plants are orchids. Most familiar orchids are those found in tropical regions.
Tropical orchids have large, showy, colorful flowers, and are often used
by florists in fancy bouquets and corsages. These tropical species are typically
epiphytic, meaning they are found growing above ground, in tree crotches
or attached to bark of other plant species. BACKTerrestrial orchids
In North America, approximately 1000 species are found throughout the continent.
Most North American species are found in tropical and subtropical areas of Mexico and Florida. In addition to these species, approximately 145 species are found in more temperate areas. These temperate species are terrestrial, growing in the soil, and perennial, emerging each season, reproducing, then entering dormancy at the end of the season. BACK
Native orchids in New York State
Of the 145 terrestrial species found in North America, approximately 60 species are native to New York State. Some of these species are quite showy, even surpassingthe beauty of their tropical cousins, while some species sport small, insignificant flowers on a miniscul
e
plant. Only one species, the weed orchid (Epipactis helleborine) is non-native
to NY, originating in Eurasia. This species is unique compared to native
species because it appears to thrive in many habitats. BACKWhy
orchids are unique
Orchids are considered
the most evolved of the flowering plants. These plants have evolved to
have specialized requirements for habitat. Each orchid
species will germinate and grow only when these habitat requirements are
optimal. Orchids are also unique in their methods of fertilization, seed
production, germination, and pollination strategies. BACK
Flower Structure
Orchids are considered monocots, distinguished from other angiosperms
by having only one cotyledon, or the leaf that first emerges from the
seed. Monocots typically have flower parts in groups of three or six,
and this is exemplified by the structure of the orchid flower. Orchids
have 3 petals, typically the showy, colorful part of the flower. Of these
three petals, one i
s
typically quite different than the other, forming the distinctive lip
common to most species. Orchids also have three sepals, situated under
and between the petals. Depending on the species, the sepals can be quite
colorful or green.
Orchids are distinguished from other plant families by the fusion of their
reproductive parts (stamen, male and pistil, female) into a column, found
at the center of the flower.
The male part of the reproductive structure is typically dislodged by
pollinators and carried to another flower, thus starting the reproductive
process. Orchids also are distinguished from many plant families by
the presence of an inferior ovary, the structure where germination takes
place and seeds are formed. Whereas most plants have
an ovary that is found surrounded by the floral structure in the central
part of the flower, the orchid ovary is found beneath the flower, appearing
more like a swollen stem than a reproductive structure. BACK
Orchids produce the smallest seeds of any flowering plant. These dustlike seeds are produced in great numbers, often over a
million seeds per plant. Unlike other plant species, these minute seeds lack an endosperm, or food source, resulting in a small embryo covered only by a thin protective wall. This lack food reserves and protection makes the seeds extremely vulnerable to their environment, resulting in a high mortality rate unless optimum conditions are found for germination. BACKMycorrhizae and germination
If a seed happens to survive and reach a suitable habitat, germination may commence. Before any leaves or roots are produced, the seed forms a relationship with a specialized fungi, or mycorrhizae, that is found in the soil. These mycorrhizal fungi actually penetrate the cells of the seed and assist in supplying mineral nutrients and to the developing embryo. As the plant develops, the fungi multiplies, penetrating additional cells and delivering nutrients and energy to the plant, allowing for development of roots and leaves. Germination and formation of a fungal association are slow processes and it may take several years before an orchid appears above ground to flower. BACK
Flowering time
Many terrestrial orchids take over 10 years to flower following germination.
During the plant’s entire life cycle, the symbiotic relationship between orchid and fungus is maintained. The fungus continues to supply nutrients and energy to the plant, allowing it to survive its time underground. The orchid may supply some photosynthetic products (sugars and starches) to maintain the fungus. Some terrestrial orchids, such as several Corallorhiza species, contain no chlorophyll and depend entirely on the fungus to for their nutrition. Many orchids can remain underground for many years, building food reserves and energy to commence flowering and reproduction. After this large expenditure of energy, the plant will return underground for several more years. During this underground phase, the orchid survives from food and energy provided from its mycorrhizal symbiont. The orchid will re-emerge when nutrient reserves are sufficient for another attempt at reproduction. This underground phase explains why many orchid species are not found in the same place from year to year. BACK
Sensitivity to the Environment
Because the evolutionary path of orchids is long, each species has had the time to adapt to a specific niche in the environment. Each species is typically associated with a specific set of habitat conditions such as nutrient availability, sunlight, and water.
For example, some orchid species need a certain amount of calcium and high pH to thrive. This group of orchids are only found in calcium-rich fens. If a certain set conditions are not met, certain species of orchids will not grow in a given area.
Because orchids are so selective, if a habitat changes in any way, a given population may perish. This sensitivity may be the result of the specific conditions needed to form a the mycorrhizal association mentioned above. Because some orchids are considered mid-successional species and are poor competitors with other vegetation, certain species actually respond positively to disturbances, such as mowing or fire. After such a disturbance, these orchids thrive and can re-populate an area. BACK
