Frozen in Time
A University of Florida researcher explores a plant preservation method that could help endangered species.
By Robert H. Wells
A University of Florida scientist is researching a method to freeze and preserve orchid seeds. Along with aiding producers, it might give endangered plants a better chance at survival.
Wagner Vendrame, an associate professor of environmental horticulture with UF’s Institute of Food and Agricultural Sciences, is trying to improve a technique known as cryopreservation, in which living cells or tissues are frozen in liquid nitrogen at minus 321 degrees Fahrenheit for later use. So far, his results from cryopreserving orchid seeds have been promising.
The Florida orchid industry generated more than $43 million in sales in 2011. It produces orchids for the specialty and mass markets using hybrid plants that can be cultivated. They aren’t in danger of extinction as many orchid species are.
By freezing seeds, orchid breeders can store them for later use if they have space constraints and are only able to germinate a portion of their seed stock, said Vendrame, who is based at UF’s Tropical Research and Education Center in Homestead. Freezing could also enable scientists to store endangered plants for future studies and restoration efforts.
“It could be a good means of preserving other types of plants that might be disappearing from the face of Earth,” Vendrame said.
There are more than 30,000 species of orchids in the world, and Florida is home to 99 of them — the largest number of naturally occurring orchid species in the United States.
Of the native orchid species in Florida, more than half are either threatened or endangered, including the ghost orchid made famous with the book “The Orchid Thief” and the 2002 film “Adaptation,” starring Nicolas Cage and Meryl Streep.
Overcollection and habitat loss are often the biggest threats to wild orchids.
In a study, published in the current issue of the journal Scientia Horticulturae, Vendrame’s team used hybrid orchid seeds to evaluate Supercool X1000 and phloroglucinol. These cryoprotectants — compounds similar to antifreeze that minimize freezing damage to tissues by preventing the formation of ice crystals within cells — are added to solutions used for pretreating living tissues before being frozen.
The team treated one group of seeds in a solution containing Supercool X1000, another with a solution containing phloroglucinol, and a control group where the solution had no cryoprotectant added. After being frozen for 24 hours, scientists removed the seeds from the liquid nitrogen, thawed them and tried to sprout or germinate them. Successful germination meant a seed had survived freezing.
Adding Supercool X1000 to the pretreatment solution only increased seed germination by about 1 percent more than the solution alone. But adding phloroglucinol increased seed germination by nearly 30 percent.
About 79 percent of the seeds treated with phloroglucinol germinated.
“So it’s pretty significant,” Vendrame says. “These are excellent results.”
The study is one of the few that has looked at phloroglucinol, which is extracted from brown algae, as a cryoprotectant for plants, he says.
Guillermo Salazar (MS ’11), a UF/IFAS Florida Yards and Neighborhoods extension agent in Miami-Dade County, is an orchid enthusiast who has studied the plants under Vendrame.
He attributes the fascination with orchids to their uniqueness and diversity.
“There are thousands of different species with diverse shapes, colors and scents,” Salazar says. “And they can be found in a variety of ecosystems, from growing on cliffs to in trees and beside rivers. It just really makes them interesting, and you want to experience them all.”
He says there are some orchid species that have disappeared completely and others that can only be viewed in private collections.
“If we could have the possibility to preserve a particular species that is endangered, then future generations would have the ability to enjoy them as well,” Salazar says.
In addition to Vendrame, study authors also included Renato Galdiano and Eliana Lemos with the Universidade Estadual Paulista Júlio de Mesquita Filho in Jaboticabal, Brazil, and Ricardo Faria with Universidade Estadual de Londrina in Londrina, Brazil.