When the days grow longer, temperatures begin to rise, and San Francisco Giants’ pitcher Tim Lincecum throws out the first pitch of the season, I know that spring has arrived in San Francisco. As new leaves appear and flowers begin to bloom, we are certain that winter has left us behind. It’s easy for us to know when spring is here, but what about the trees and flowers themselves? How do they know when to drop their leaves, and when to bloom?

Scientists believe they’ve discovered a special molecule in plants that gives them the remarkable ability to “remember” winter and to bloom on schedule in the spring. Their results are reported in the December 2 issue of Science Express.

Sibum Sung, molecular biologist at the University of Texas and one of the paper’s authors, was searching for a mechanism that allows plants to recognize spring and – more importantly – distinguish between spring and a brief warm spell during winter. The key, Sung found, was the plants’ ability to remember that winter had passed.

“Plants can’t literally remember, of course, because they don’t have brains,” says Sung. “But they do have a cellular memory of winter, and our research provides details of how this process works.”

The process Sung referred to is called “vernalization.” It allows a plant to properly come out of hibernation during winter so that it can bloom. But experts have never really understood the genetic basis for how vernalization worked.

Until now. Sung and his co-author Jae Bok Heo dug deep into the DNA of arabidopsis, a small flowering plant related to mustard and cabbage. As they scoured the lines of genetic code, they discovered that arabidopsis’ DNA coded for a molecule they called COLDAIR.

The authors’ experiments revealed that while the plant hunkers down for the winter, COLDAIR is switched off. After 20 days of consistent freezing temperatures, COLDAIR gets switched on. This begins the 10 to 20 day process of preparing the plant for spring. Once complete, the plant is ready for warm temperatures, and other pieces of genetic code help the plant to bloom.

As many of us know, this system isn’t perfect. Sometimes flowers do bloom early, and they pay the price when temperatures quickly return to freezing. But over millions of years of evolution, COLDAIR has helped create a kind of “memory” in generations of plants, telling them when there’s been at least a month of cold and that spring might be just around the corner.

Of course, many questions remain. Sung admits they still don’t have the other pieces of the puzzle, like how does the plant know it’s been at least 20 days of cold temperatures? “That is one of the next questions we have,” he says. “How do plants literally sense the cold?”

The particular mechanisms require further study, but as long as COLDAIR keeps working, flowers will give us one more sign when spring has sprung.

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image by Roepers/Wikimedia

A species’ survival often depends on how skillfully they can beat out another species for food or other resources. But sometimes, a species’ survival depends on how well they work with their neighbor. If each organism helps the other, they can both flourish. This process, called “symbiosis,” explains why bacteria thrive in our guts (because we thrive with them), how sharks don’t seem to mind the so-called “cleaner fish” that dart in and out of their mouths, and how delicate coral reefs can grow to the size of a small continent.

There are thousands of examples of symbiotic relationships on planet Earth. But has this practice always existed? In a study published last week, scientists uncovered evidence of a symbiotic relationship that existed over 470 million years ago. A relationship that paved the way for nearly every land organism on Earth.

In the November 2 issue of Nature Communications, a research team from the Royal Botanic Gardens and the University of Sydney pieced together earlier days of complex life by studying one of the most ancient land plants still in existence, the thalloid liverwort. Liverworts, often a nuisance in backyard gardens and greenhouses, have a small and flat ribbon-like structure.

Scientists have long suspected that the secret to the liverwort’s early success was a relationship with fungi living in the soil. But no one had been able to test it. Until now.

The team placed both liverwort and fungi in tightly controlled growth rooms to recreate Earth’s early days – hot and volatile. They found that when the fungi colonized the liverwort (a common fungal practice), the liverwort vastly improved its ability to take in carbon dioxide (CO₂). As a result, it grew and reproduced faster than if no fungi had been present. The fungi not only improved the liverwort’s ability to grow and reproduce, it helped the liverwort release substantial amounts of oxygen into the atmosphere. Something sorely lacking in Earth’s earliest days, and something for which we should all be thankful.

So what did the fungi get in return? They fed off the extra carbon the growing plants produced. In one experiment, the team found that just one liverwort plant could support fungi encompassing two tennis courts.

Professor David Beerling from the University of Sheffield, one of the authors of the study, was excited about how this research can help shed light on the earliest days of our planet. “By studying these ancient plants,” he says, “we open a window on the past to investigate how the earliest land plants evolved.”

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Creative Commons image by Eric Guinther

Well, enough is enough! Over the past two weeks, we have seen some very exciting plant news, including recent funding for new research! From ScienceInsider today:

Long the impoverished Cinderella of the biological research kingdom, plant science has just had a visit from the fairy godmother. Today the Howard Hughes Medical Institute announced it would hire up to 15 plant biologists and spend $75 million over the next 5 years to enable these new HHMI researchers to pursue creative and fundamental research.

This research will also be funded by the local Gordon and Betty Moore Foundation.

Just in time, too. Also in the news today, one-fifth of the world’s plants are at risk of extinction. New Scientist runs the numbers for us:

The Sampled Red List Index for Plants indicates that 22 per cent of all wild plant species face extinction, comparable to the figure for mammals (21 per cent) and higher than that for birds (12 per cent). Of the threatened plant species, 63 per cent are found in tropical rainforest areas which could soon be cleared.

Also in science news recently, daisies. Daisies and their kin (which include sunflowers, dandelions, lettuce, and artichokes) are part of one of the largest plant families in the world. And new research, published last week in Science, confirms that they’re also really, really old. Scientists always thought that the family traced back about 50 million years, and now they have evidence—a fossil found in South America. From Nature News:

Complete with large flower heads, leaf-like structures and slender stems, the remains come from rocks in Patagonia that are 47.5 million years old, dating from the Middle Eocene.

Finally, published last week in the Journal of Ecology, 150 year-old pressed orchids in museum herbaria. That may sound like old news, but these antique flowers provide a new source of data for studying climate change. According to Wired:

Scientists have used the carefully labeled and dated specimens of the early spider orchid, Ophrys sphegodes, to examine the affect of spring temperatures on flowering. The flowers were collected between 1848 and 1958.

The results… found that for a 1.8 degree Fahrenheit increase in the spring temperature, the orchid flowered 6 days earlier.

As The Great Beyond Blog in Nature puts it:

Every year, the media reports that the transition between winter and spring is arriving earlier, and that plants are no longer blooming when they used to. But accurate records of the effects of changing temperatures on plant flowering times are patchy at best… The shortage of available data may not be a problem for much longer.

That’s because in addition to the orchids, there are literally billions more specimens held in natural history collections in museums and herbaria. Some specimens date back to the time of Linnaeus (who devised our system of naming plants and animals) 250 years ago. Climate tracking just got a lot easier, thanks to plants.

So let’s give it up for plants. It’s about time!

Image: Science/AAAS