It’s been a while since my last blog post. I’ve had a busy month: launching a new semester with students, learning about a new sport with one of my kids, enjoying the last of the warm days outdoors, finding some local apples… and discovering the world of competitive baking on TV. But I’ve kept my eyes open for interesting science stories to share. They seem few and far between at the moment. Here in the U.S., politics, devastating hurricanes, and climate change have dominated the headlines the past few weeks. (At some point, I’ll probably update my recent post about climate change.)
But for now, I’d like to comment on a science story that for a brief moment a few weeks ago dazzled my online news feeds with colorful, dramatic, and informative images about new insights into how plants respond to their environment. It’s also a story about “famous” plants, and the incremental nature of science that may wow us only from time to time. In the classic fable of the tortoise and the hare, the hare is quick and clever and flashy and runs ahead in fits and starts. The tortoise, undeterred, moves along at its own unremarkable pace, but ultimately makes slow headway toward its goals and wins the race. Our steady hero this time is a plant that regularly reveals interesting findings in many areas of science. One day, it had a good heat in the race and got its picture in the paper. And that’s worth celebrating!The plant in question is a nondescript member of the mustard family called Arabidopsis thaliana; scientists call it Arabadopsis, not for short. It is has become a model plant for all kinds of research related to plant biology, from anatomy, physiology, genetics, flower formation… you name it, someone’s probably tested their idea using this plant. When scientists gather a lot of data from the same organism, it can build an more complete picture—like a jigsaw puzzle, piece by piece—of how a type of organism works. And then we can compare it to other living things and look for interesting similarities and differences.
The plant news story in September was sparked by a scientific report in the journal Science by team of collaborating researchers based in Japan and the United States. At the heart of their study was their new insight that plants can send calcium ions through their tissues in a wave to communicate that a signal from the environment was received elsewhere on the plant. The trigger is a molecule called glutamate, which causes signaling responses more well understood in animal cells in its role as a neurotransmitter to cause neurons to send chemical signals from cell to cell. Masatsugu Toyota and colleagues showed that if an Arabidopsis leaf is compromised—such as when it is nibbled by a caterpillar—a wave of chemical signal reaches far across the plant in just minutes and helps the plant respond to the attack by mounting a chemical defense system of its own all across its body.
At this point, I’ll direct you to the news reporting for the complete scoop. Gloria Muday and Heather Brown-Harding from Wake Forest University wrote an accompanying “Perspective” article in Science, providing a thorough technical overview of the new finding and its implications alongside the primary report. Ultimately, science journalists such as JoAnna Klein at The New York Times shared the story to the rest of us (“Watch Plants Light Up When They Get Attacked”), including in their stories some of the fascinating video that Toyota and the team captured to show how the glutamate/calcium signaling moves through the plant. They used a fluorescent molecule to tag the chemicals in the plant so we can actually see the response with our eyes. I’ll wait while you go check out the videos in Klein’s article above. Or in this one, from Nick Lunn at National Geographic, or here, from a CBS news affiliate station.
Scientists find this study interesting as providing one piece of information in a long trail of research to understand how plants— which are seemingly unmoving and certainly are stuck in one place for most of their lives—can respond when under attack. The Arabidposis “tortoise” plant has revealed its secrets slowly over a period of many years, one experiment at a time. But this time, the science made a connection with better understood animal communication systems, and with gorgeous video that makes a compelling story. It was enough to break through the other concerns of humans for a day or two, and give us all something to marvel at, with oohs and aahs about the striking video footage.
Scientists didn’t just wake up one day and make this observation. The research on plant signaling has moved along steadily for decades, from many different angles and in different types of plants. Take this news story from last May: “Plants use underground communication to learn when neighbours are stressed,” by Josh Gabbatiss from The Independent. This time, researchers from Sweden were looking for below-ground signals that might trigger changes in corn responses when plants brush up against their neighbors (or pests) above the ground. Roots and their associated fungi may create another avenue for chemical communication in this species that humans have bred to grow in close quarters in fields. Because of its agricultural importance, corn is another sturdy tortoise in the marathon of scientific research and discovery.Finally, I give you one more story about a plant “tortoise” in a long race. This one didn’t make headlines. It’s just a single report in the American Journal of Botany from their September issue. Researchers from the University of Alberta (Canada) reported how stressful it is for the “sensitive plant” to be touched repeatedly. This plant, Mimosa pudica, folds up its leaves very rapidly when they are contacted by an object. If you simply run your finger along its leaves, the leaves close up in just a matter of seconds (watch a video here). People have been studying this response for decades and have learned quite a bit about the system. Yet, questions remain. So in this latest study, researchers Tan Bao and colleagues asked how much being touched impacted growth of the plant. If you pester a Mimosa plant’s leaves frequently during the day, it doesn’t grow as well as if you don’t. (The plants automatically fold up their leaves at night, so poking plants in the dark doesn’t impact their growth as much.) Figuring out how much energy it takes to fold up leaves vs. grow bigger is an interesting question, and this study moves us one space forward in understanding the different parameters of the question.
So yes, plants can move. And plants can respond to their environments. The more we look, the more new discoveries we find. Last spring, I wrote a blog post about “The Underappreciated Lives of Plants.” As a scientist—and a fan of food and shade and beauty and other fine aspects of plants in my life—I always enjoy when plants make headlines, and I enjoy reading about them and sharing them. And when the stories don’t break through, rest assured that research into the basic lives of plants carries on at a steady pace and enriches our curiosity and understanding of the world around us. Slow and steady wins the race, at least sometimes.