Thousands of tulips are rising to the occasion, just in time for Zoo Blooms at the Cincinnati Zoo & Botanical Garden. They survived what everyone agrees was a long, cold winter.
But long and cold are relative terms. Especially when one considers that the zoo has kept some plant materials in a deep freeze for more than two decades, in conditions so cold it's hard for the human mind to comprehend.
The CryoBioBank at CREW, the zoo's Center for Conservation and Research of Endangered Wildlife, contains one of the world's oldest and most diverse frozen collections of wild plant materials – more than 3,000 samples, including seeds, spores, shoot tips and pollen, many from endangered species. They are preserved in liquid nitrogen at a temperature of minus 196 degrees Celsius, which, on the Fahrenheit scale, is 321 degrees below zero.
"When people say, 'It's hot as hell,' this would be the opposite," said a smiling Dani Ballesteros, a post-doctoral researcher at CREW.
Now, though, about one-third of the collection is coming out of the cold so CREW scientists can test whether seeds and other materials survived and how they were affected genetically. The study received a three-year grant of $461,948 from the Institute of Museum and Library Services.
"This is a fairly new science," said Valerie Pence, CREW's director of plant research. "(Materials) just haven't been in storage that long to really analyze them. Our collection is getting to the point where it can provide a lot of good information."
It's important to know if plant material can be cryopreserved – stored in ultra-cold liquid nitrogen – because sometimes other preservation methods don't work well, or the plant doesn't produce seeds. And while one way of preserving plants is simply to grow a lot of them, "you need a lot of space to preserve as much genetic diversity as you'd like," Pence said.
Not so with a frozen garden.
On a larger scale, such work helps ensure the survival of a wide variety of plant species, many of which are threatened with extinction. "Every plant, like every animal, is a part of the ecosystem," Pence said. "There are a lot of interdependencies."
Humans, she noted, essentially get all their food from plants, and many of the medicines in use today were derived from them. Yet only a fraction of plant species have been tested for their usefulness.
"We could be losing a lot of things we don't even understand yet," Pence said. "Would you throw away your Christmas presents before you opened them?"
CREW scientists are finding that most of the seeds removed from the CryoBioBank are germinating and growing normally. But there are exceptions.
Some seeds, including poplars and willows, are considered "short-lived" because when stored at minus 20 degrees Celsius – the standard temperature of most seed banks – they typically die within 10 years, Ballesteros said.
CREW has found that storing such seeds in much colder liquid nitrogen "extends their viability longer ... but we also have seen that they are aging and dying," he said.
While Ballesteros is focused on plant survival, Megan Philpott, a doctoral student at the University of Cincinnati, and her adviser, Theresa Culley, an associate professor of biological sciences, will study the samples' genetics. "We're trying to develop a method where we can look at all the DNA in different cells and see exactly what's happening," Philpott said.
Knowing how long certain plant materials can be stored in liquid nitrogen could be useful for the forestry and agriculture industries, Ballesteros said, as well as botanical gardens and organizations that focus on conservation of wild and endangered species.
"The goal of any conservation collection is to maintain a backup for plants in the wild, and also to provide (plant) material for restoration," Pence said. "The restoration part is a very important piece in all this. We hope that anything we can preserve could be used eventually for that purpose."
An example is the Cumberland sandwort, a rare, federally endangered plant that lives in the sandy soil of the sandstone rock formations in southern Kentucky and northern Tennessee.
CREW collected such seeds from Tennessee in 1994, established 10 genetic lines in its tissue culture lab and stored samples of each line in liquid nitrogen. In 2005, CREW took 77 plants from its lab, and with help from the U.S. Forest Service, planted them in Daniel Boone National Forest. Last August, CREW returned to the site and counted 160 plants, Pence said.
What's more, some formerly frozen specimens are grown on zoo grounds. That job falls to Brian Jorg, manager of the native plant program.
The Cumberland sandwort needs soil that is far more acidic than Cincinnati offers, so Jorg imported sand from McCreary County, Ky. Then he built a sluice, so the sand would stay damp, but not too wet. He took readings of how much light the plant receives in the wild, and reproduced that here by using burlap coverings.
The result: "We are the only place that's ever grown that plant in cultivation." ■
Where: Cincinnati Zoo & Botanical Garden
When: Through April; best time to see 100,000-plus tulips is mid-April.
Cost: Free with zoo admission; adults, $15; children and seniors, $11; under 2, free.
Tunes & Blooms concert series: 6-8:30 p.m. every Thursday through May 1. Zoo admission free after 5 p.m. (Parking is $9.)
April 10: Jake Speed & the Freddies and Shiny and the Spoon
April 17: The Cliftones
April 24: Green Light Morning and DAAP Girls
May 1: Comet Bluegrass All-Stars and Bulletville
Tulip luncheon: 11 a.m. April 9. $75. Call 513-487-3327.