Presented at the 2000 Houston Orchid Society Summer Workshop
and published in the Proceedings
Many orchids are pollinated by solitary Euglossid bees in the tropics, and by social (hive-forming) bumblebees and wasps in temperate zones. Bees carry
orchid pollinia on their thorax. Many bees can't see red (they are red-blind), so they are primarily attracted to orchid flowers that are yellow, blue-green, blue and violet. They also see ultraviolet (UV) light reflected by flowers that humans are unable to perceive. Many cattleyas are bee-pollinated, along with schomburgkias, encyclias, and some epidendrums.
At higher elevations, birds take over from bees, but one of the major differences is that birds have no sense of smell, so bird-pollinated orchids
are generally not fragrant. Also, birds and butterflies are attracted primarily by red, pink, and orange hues. Flowers that are bird-pollinated
are often tubular and have a heavy callus on the lip. Within the cattleya
alliance, birds and butterflies are both found to pollinate epidendrums, and
birds are also attracted to laelias. For instance, hummingbirds are also seen pollinating the red Comparettia falcata and Laelia milleri.
Fly-pollinated orchids are usually colored dull-purple and offer a radial shape. They include some epidendrums.
Moth-pollinated orchids are generally light colors with flags and frayed
petals, such as some encyclias and epidendrums. Sphingid moths pollinate
the green and white brassavolas.
In their article on "Hybridization and Inheritance in Orchids," pp.261-314 of Withner's 1959 book, authors Lenz and Wimber set the timeline for the study of genetics. C.C. Hurst apparently began experimenting with orchids in 1897, just prior to Gregor Mendel's famous paper on heredity, published in 1900. By 1909, Hurst published his first paper, on the inheritance of albinism within cattleyas, laelias, dendrobiums, and paphiopedilums. It was later discovered that lip color in cattleyas is inherited separately from petal and sepal color. In 1958, Mehlquist used the term "semi-alba' in his talk at the 2nd World Orchid Conference (WOC) in Honolulu to identify orchid flowers that were primarily white but carried a colored lip.
Color inheritance may be based on a single gene or multiple genes, which can act either dominant or recessive. Additionally, there are intensifier or inhibitor genes. In cattleyas, yellow is usually recessive, hidden by genes for purple. In laelias, yellow is usually dominant and masks purple. Pigmentation patterns can be expressed differently in the floral and vegetative parts of plants, and can be distributed in different manners, either solely in the epidermis, or more uniformly throughout the plant tissue.
Wither (1988) mentions that there are at least three classes of pigments
in cattleya flowers:
(1) Anthocyanins (water-soluble vacuolar pigments), which are flavonids mainly responsible for blue-mauve-pink-lavender-purple-magenta-red tones. Anthocyanins are comprised of a color compound (anthocyanidin) bonded to a sugar molecule. Common color compounds include "pelargonidin" (scarlet-red), "cyanidin" (blue-red), and "delphinidin" (pure blue, but not found in any orchids). Anthocyanins can be modified through the addition or subtraction of hydroxyl groups or changes in pH of the "cell sap". Acidic sap favors reds and whites, and alkaline sap favors blues and yellows. Typically, sepal and petal tissue would contain two or three types of anthocyanins, and lip (labellum) tissue would have several additional anthocyanins contributing to the typically richer color. Anthocyanins may be co-pigmented with light yellow flavonids.
(2) Carotenoid derivatives (fat-soluble pigments in the chromoplastids or
in chloroplasts) form yellow and orange colors in flowers. These plastid pigments are not sensitive to pH.
(3) Chlorophyll (in chloroplasts) produce different shades of green. Chlorophyll alone produces a dark jade green, while chlorophyll in combination with carotenoids result in a clear, pale green. Chlorophyll, carotenoids and anthocyanins all together result in bronze and brown flowers. "Muddy" colors, on the other hand, result when anthocyanins are present in the surface layers, over chlorophyll in the deeper tissue, or carotenoids in the sepals and petals.
Genetic variation produces alba and semi alba forms which lack pigments, albescent or xanthotic forms, coerulea (blue or mauve), along with splash petalled and picoteed peloric varieties. Red flowers are a result of a combination of the yellow/orange carotenoids and redder anthocyanins. True red has no magenta component. It's important to remember that color perception is highly dependent on the light source.
Light Source, Photographic imaging
The color of light varies with the wavelength, and even our artificial electric lights can be highly variable. When viewing photos and electronic images of orchid flowers, another factor to consider is the type of film or processing used. Every film has a different color balance. Kodachrome, the transparency film of choice for many years past, was balanced in favor of red. Ektachrome films have more of a slant to blue/green. Many hobby films enhance colors, leading perhaps to greater color saturation than the in real-life.
Criteria for Judging Color
According to Section 6.1.1 of the American Orchid Society (AOS) Handbook
on Judging and Exhibition, among the criteria for judging cattleyas and
allied genera are:
AOS awards are based on a 100 point scale. Color accounts for 30 points of the general point scale for quality awards (6.2.1) and for 30 points of the Cattleya point scale (6.2.2), allocating between general color (15), sepal & petal color (7) and lip color (8). Color is considered part of "Harmony", which accounts for 30 points of the total possible points for orchid arrangements (6.3.5); "Harmony" also encompasses Texture and Relation to Container. And within the point scale for the Certificate of Horticultural Merit (CHM; 6.3.2), color only accounts for 12 points.
Beauty is in the eye of the beholder!
(1) Cattleya skinneri var. alba - species from Mexico and Central America
(2) Laelia rubescens var. alba - species known in Guatemala as "Flor de Jesus"
(3) Brassavola nodosa var. grandiflora - The "Lady of the Night" orchid; widespread
(4) Blc. Love Sound - white sepals and petals with yellow lip
(5) Lc. Blue Magic - whitish sepals and petals with "blue" lip
(6) Dialc. Silver Toy - shell pink
(7) Bc. Morning Glory - primary B. nodosa hybrid with pink striated lip
(8) Broughtonia jamaicensis - medium pink species with clustered flowers
(9) Blc. Rosebud - reddish lip and slight red splash on pink petals
(10) Cattleya Brabantiae - yellow and red markings on lip
(11) Laelia pumila - Brazilian species, solid deep rose-purple; up to 4" flowers
(12) Sophronitis wittigiana - dwarf species from Brazil & Paraguay; up to 3" flowers
(13) Oerstedella schweinfurthiana - pink lip and reddish sepals and petals
(14) Potinara Elaine Taylor - deep red with white column
(15) Encyclia diota var. atrorubens - deep red with almost brownish overlay
(16) Hawkinsara Koolau Sunset - dark red with pink column
(17) Cattleytonia Cosmo-Sanguine - rich red with slight yellow in lip
(18) Cattleya aurantiaca - reddish form of the species from Central America
(19) Slc. Jungle Elf - red with yellow lip
(20) Lctna Happy Face - peloric appearance, pink sepals
(21) Slc Precious stones - dark red spots and yellow lip
(22) Sophronitis coccinea - red-orange here, but often scarlet
(23) Sophronitis acuensis - same; can have orange lip
(24) Yam. Redland Sunset - orange with a red/pink lip
(25) Slc Sunset Nugget - orange with deeper orange lip
(26) Lc Highland Treat - pumpkin orange!
(27) Slc Jungle Beau - light orange with red lip
(28) Bl Martha Miller - deep yellow gold with spidery nodosa form
(29) Blc Meila - gold with red spotted lip
(30) Encyclia (Euchile) citrina - solid yellow pendant flowers; sweet scent
(31) Blc Love Sound - solid concolor yellow
(32) Epidendrum Orchid Jungle - brown with dark lavender lip
(33) Encyclia bractescens - brown Mexican species with pale lavender lip
(34) Epidendrum stamfordianum - greenish Mexican sp. with brown spots
(35) Lc Roy Finley - green hybrid with dark spots
(36) Epidendrum raniferum - green species with brown spots
(37) Epc Little Sweetheart - clear green with stark white lip
(38) Epidendrum marsupiale - clear green species
(39) Encyclia unaensis - yellow/green species with white lip
(40) Encyclia radiata - pale green resupinate species with striped lip
(41) Lc Alarcon - pale lavender hybrid with bluish lip
(42) Cattleya jenmanii var. coerulea - species; same color
(43) Cattleya skinneri var. coerulea - species; same with yellow eye in throat
(44) Diab. Alice Hart - dorsal sepal and petals purple, lat. sep & lip lavender
(45) Cattleya lueddemaniana - classic lavender cattleya
(46) Encyclia cochleata - the "Cockleshell Orchid", dark lip, green sepals and petals
AOS Handbook on Judging and Exhibition
Hilda Simon (1975), The Private Lives of Orchids
van der Pijl and Dodson (1966), Orchid Flowers - Their Pollination and Evolution
Carl L. Withner, Ed. (1959), The Orchids - A Scientific Survey
Carl L. Withner (1988), The Cattleyas and their Relatives, Vol. 1
(subsequent volumes 2 through 6 contain a plethora of useful information)
© Nina Rach, email: firstname.lastname@example.org