Orchids

This topic submitted by Geoff MacIntyre ( geoffmacintyre@hotmail.com) at 11:55 PM on 5/15/04.

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Tropical Field Courses -Western Program-Miami University


Orchids
By N. Geoffrey MacIntyre
Tropical Ecology- Professor Hays Cummins
University of Cincinnati- Miami University consortium agreement
Spring 2004


"As we delight in the strange and exotic beauty of orchid flowers it is salutary to reflect, that we are, in essence looking at their genitalia."
Unknown British biologist

I began this topic out of an interest in these strange and beautiful plants. I have one living in my shower that has only bloomed once in 2 years. I had no idea when I began that the topic of Orchids is inherently overwhelming. For example, there are more than 25,000 species of Orchids so far identified in over 450 genera, and as many hybrids have been described or bred by humans. Can you imagine what 50,000 different variations on the theme of "orchid" could look like? I can only think of about 10 different kinds of orchid that I've seen myself, maybe 100 more or so I've seen a picture of. We all have a lot of work to do "orchid spotting" in Costa Rica.
General information about Orchids
Members of family Orchidaceae are herbaceous, long-lived perennials. They are masters of adaptation- living in some of the most demanding climate zones, and displaying a bizarre menagerie of form, color and function. Orchids belong to the phylum Magnoliophyta, class liopsida, and order orchidales. Most orchid species, and 88% of orchids in Costa Rica, are epiphytic. This means that they live above the soil attached to another plant or structure. However, most temperate species, and all arctic species are terrestrial.
Individual species are very specific in their needs, and are very adapted to the specific niche they occupy in the wild. Wild orchids will almost certainly die if removed from their original location- unless similar temperature, light, humidity and nutrient requirements are provided.
Epiphytic species usually have a swollen pseudo bulb- a food and water storing organ derived from the stem, and rhizomes- a stem/root apparatus that anchors the plant to the substrate, provides growth, and can, in some cases, provide vegetative propagation. This is called a sympodial “two footed” growth form. Other species display a monopodial, “single footed” growth form lacking rhizomes and pseudobulbs, instead having fleshy, succulent leaves for storage, and aerial roots that may be photosynthetic. These orchids grow upward from a single point by stem growth, and by adding leaves to the apex of each stem.
Orchid Reproduction
First, let’s talk about parts, because orchids are a lot different than you and I. First, orchid flowers have both female and male organs, called the pistil and the stamen, fused together in a structure called a column, or the gymnostemium. Orchid ovaries are “inferior” which means flower parts ripen with the fruit and seeds, instead of remaining separate (and falling off).
When an orchid is ready to reproduce, it produces flowers with a three petal, three sepal flower arrangement. One of the three petals is usually modified into a decorative petal called a labellum. Waxy, lumpy collections of 2-6 individual pollen grains, called pollina, are produced from a single anther atop the column. Many orchid species have modified flower forms, and may produce nectar from their labellum because they depend on insects or other creatures, like bats, to carry these pollina to other individuals for sexual reproduction. These orchids have often evolved to utilize a single species as their exclusive pollinators. They may mimic insect forms or markings in their flowers, and may create large volumes of pheromones that closely mimic an pollinator’s sexual pheromones to attract would be lovers to pollinate flowers instead.
Once pollinated, orchids produce tiny, wind-dispersed seeds that lack an endosperm “food store” inside. Instead, most orchids package microscopic, mycorrhizal “starter fungi” with their seeds to help them germinate. These fungal helpers bring water, nutrients, and food to the developing embryo as it germinates, and will continue to do so the rest of the plant’s life.
Orchids belong to a relatively new group of plants. As a result, they are still in a “fluid” genetic state, which allows them to share a great deal of their genes with each other. This is demonstrated by the readiness that orchid species will inbreed and produce hybrid varieties, and the large variety of forms that can be found in a single species.
Smallest and largest of orchids
Below left is a tiny orchid, Platystele pedicelaris, which lives in the Belize Botanical Gardens. It’s flowers can be smaller than 1millimeter. Below center and right is Grammatophyllum speciosum, the "sugarcane" or "tiger" orchid. This giant orchid is native to Southeast Asia, grows 3 - 7 meters tall, and resembles a rather stalky, grassy, sugarcane plant.

Distribution worldwide
Orchids are present on every continent but the Antarctic. They thrive in lowland rainforests, dry beach dunes, and even mountainsides up to 14,000ft!
Geography and Climate
Costa Rica is a small, tropical country with a central volcanic mountain region that divides eastern and western coasts. These mountains gradually rise to their tallest point, Cerro Chirripó, (12,454 feet) in the south near Panama. Weather is divided into only two seasons, a “wet” season lasting April to November, and a “drier” season the rest of the year. Temperatures here vary more with altitude than from other factors. There are three distinct climate zones; the central “Meseta” province characterized by valley-plateau geography that varies in elevation from 3000- 6000 feet. Mild, spring-like temperatures (59 to 77 degrees Fahrenheit) last all year round. The beaches and coastal plains of the warm, humid and rainy Caribbean coast have temperatures from 77 to 100 degrees Fahrenheit. High altitude “cold zones” above 6000 feet are characterized by windy but drier conditions
Lifestyle
Most orchid species are epiphytic- highly evolved plants that grow free of the soil. These most commonly grow on trees, but can be attached to almost anything if conditions are right. These orchids get nutrients from "stem flow"- water that landed on leaves and branches and runs down the tree, bringing with it dissolved nutrients from animal droppings. Orchids, as in most plants, are always found in a mutualistic association with mycorrhizal fungi, who do most of the work in capturing water and nutrients and bringing them to the rhizome tips of orchids.
Ecology
Costa Rica has at least a half a million species of flora and fauna- about 5 percent of the world’s known species. The country can be divided into 12 of Holdridge’s life zones - tropical moist, tropical wet, tropical dry and rain forests dominate, with premontane, lower montane and tropical sub-alpine wet, moist and cloud forests making up a small percentage of the rest.
What it means to be unique: specialists versus generalists
If you take a goldfish, a cockroach, a multi-floral rose, a dandelion, or a zebra mussel anywhere on Earth, (especially a human-inhabited area) it will likely thrive. These species are generalists. They do well in disturbed habitats. Orchids are specialists. They have evolved to exploit niches that other plants cannot. A dandilion would shrivel on a sand dune where some orchids thrive. Multi-floral rose could never survive the sun and aridity of a forest canopy- especially if it had to live without soil as most species of orchid do. If a canopy dwelling orchid is moved up or down 10 meters, it is as doomed as a fish out of water.
They have evolved physically and chemically; and have dramatically changed their lifestyle to suit their ecosystem, becoming a better and better fit to their niche even as their ecosystem evolves slowly with them. Because of this, it is difficult for us as humans to understand the uniqueness of organisms like orchids. The plants and animals we come into contact with on a regular basis are generalists- successful species that thrive in disturbed or quintessentially human habitats. Cattle, corn, domestic dogs, dandelions and even wild animals like deer. Often we have removed the truly unique creatures before we even noticed them- or our cat did (example: songbirds). We are rarely exposed to the rare, unique, and highly specialized animals and plants, because they cannot live with us unless we make, or preserve room for them.
Gallery of wild orchids we are likely to see if we look hard on the trip
See Geoff’s Orchid book (in mail tomorrow or Monday)
Other places to see orchids:
Krohn Conservatory - Cincinnati
http://www.cincinnati-oh.gov/cityparks/pages/-3452-/
Cincinnati Zoo and Botanical Gardens
http://www.cincyzoo.org/


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