Slippery Cells and Gestures

Findings Log / by The Editors /

In this week’s Findings Log, we take a look at new research on desiccated plants, a cloud-sparse young Earth, and the silent parts of conversation.

Findings Log is a look at some of the research and academic papers that have recently caught the eyes of Seed’s editors, Lee Billings, Joe Kloc, and Maywa Montenegro. For more recommended reading and occasional insights, follow them on Twitter.

Read the paperGoldin-Meadow et al. Psychological Science. April 7, 2010

Surely You Gesture
Interviews with suspects and eyewitnesses are a crucial part of the legal system. These exchanges are transcribed and then analyzed by lawyers and experts who search for peculiarities and inconsistencies as they attempt to build accurate accounts of significant events. Given the importance of these transcripts, it stands to reason that they should be subject to constant scrutiny and refinement. Researchers at the University of Chicago are doing just that by investigating how hand gestures not recorded on transcripts can influence a conversation. The following example from a study published recently in Psychological Science sums this idea up nicely:

Interviewer: “What was he wearing?”
Child: [silence]
Interviewer: “Was he wearing glasses?”

To someone who wasn’t present at the interview, this transcript gives the impression that the interviewer is giving a leading question—perhaps making the child think the person in question was wearing glasses. But in fact the child had responded to the interviewer with a gesture indicating that the subject was wearing glasses. The interviewer was verbalizing the child’s response, not influencing it. The researchers conducted this kind of experiment with 39 different children, interviewing each subject four times about a particular event, and studying the influence that gestures had on the conversation. Among other findings, the researchers showed that the most correct details of an event were conveyed when the gestures of the child and interviewer were both considered. The most interesting finding is perhaps that a gesture in one interview can affect answers in another interview weeks later. It is no surprise that nonverbal cues influence conversation, but what is fascinating about this study is that it illustrates how, by neglecting the unspoken dimensions of an interview, transcripts can present skewed—and in some cases downright contradictory—accounts of an event.—JK

Read the paperLayton et al.
American Journal
of Botany

March, 2010

Pumping Up Plants
Plants are a bit like those magic grow capsules we all played with as kids—give them water and they plump up and function like they’re supposed to. Starve them of H2O and they’re not very active (or fun to play with). In the case of plants, the cells shrink, collapse inward, and destroy the interplay of chemicals and enzymes inside. With climate-change-induced drought an imminent global concern, understanding how hydration—or lack thereof—affects plants seemed like a worthy pursuit to biologist Ronald Balsamo and engineer Bradley Layton. They knew that some species, like the aptly named “Resurrection fern,” (Polypodium polypoidioides), can survive extreme water loss, up to as much as 95 percent of their original water content. But they didn’t know exactly how the fern’s cells remain viable. Their quest for answers led them to tag-team on a novel biomechanical investigation of the plant’s drought resistance. As they reported recently in The American Journal of Botany, when the Resurrection fern is subjected to dry conditions, it churns out a particular class of proteins called dehydrins. An abundance of dehydrins had been found before in dessicated plants, but this was the first study to discover that dehydrins—which have a negative charge, and therefore attract and sequester water—also clump near the plant’s cell walls. From a biomechanical perspective, the authors point out, this is extremely interesting: The water-surrounded dehydrins may actually allow water to serve as a lubricant between either the plant cell membrane and the plant cell wall or between individual cell wall layers. The physical stress of shriveling up is enormous—usually damaging cells to such an extent that the plant eventually dies. So a watery lubricating jacket, they argue, could be essential in drought resistance. With funding from the USDA, the researchers now plan to investigate a similar hypothesis in food crops. If the dehydrin gene could be engineered into other species, they believe, the potential for agriculture could be enormous. Maize, for example, can only withstand water loss of about 20 to 30 percent before dying. Rice is often flood-irrigated, but not on thousands of rain-fed farms across Southeast Asia, where concerns are now escalating about drought. Perhaps with a boost from the Resurrection fern, these crops will one day rebound from intense dry spells, almost as if by magic.—MM

Read the paperRosing et al., Nature
April 1, 2010

Partly Cloudy with a Chance of Controversy
For much of its history, the Earth has been more or less an alien world. Its current life-friendly configuration, with large continents scattered across a global ocean of water, sheltered beneath an oxygen-rich atmosphere dense with clouds, is just a fleeting moment in geological time. Turning the clock back to the likely point when life began, some four billion years ago, yields a dramatically different situation. Most notably, the vagaries of astrophysics tell us that back then our star was 25 to 30 percent less luminous than it is now. While that may not sound so bad, such a decrease in solar output today would probably turn our planet into an uninhabitable iceball. Yet the geological record indicates that liquid water was abundant on the early Earth, and clearly life somehow managed to emerge. So, in the weaker light of a younger Sun, how did our fledgling world avoid freezing to death? This is the “faint young Sun” paradox. First described by Carl Sagan and George Mullen in 1972, it has resisted easy explanation for nearly 40 years.The solution favored by Sagan and many of his colleagues invoked higher concentrations of greenhouse gases like methane and carbon dioxide in the early Earth’s atmosphere, which would trap radiation and warm the planet. Now, a new study in Nature shows that mineralogical data doesn’t support that hypothesis, and suggests greenhouse warming wasn’t required at all. Minik Rosing and his co-authors posit instead that the early Earth had fewer clouds and smaller continents, both of which reflect away warming sunlight. Correspondingly, more of the ancient Earth’s surface was ocean, which efficiently soaks up solar radiation. As pointed out in an accompanying commentary by veteran geoscientist James Kasting, this hypothesis is quite plausible, but by no means definitively solves the paradox.

Read the paperKaroff and Svensmark, submitted to the arXiv on March 31, 2010

Another study, by Christoffer Karoff and Henrik Svensmark, also says that a dearth of sunlight-reflecting clouds maintained early Earth’s habitability. But the researchers’ decidedly speculative conclusions come from astrophysical data, rather than the annals of geology: they studied a nearby Sun-like star, Kappa Ceti. Surprisingly, while Kappa Ceti seems to be in its faint, young phase, it’s still belching out huge high-energy flares at far greater rates than our modern Sun. The implication, then, is that our Sun was similarly active during its youth. If you’re dubious about what this has to do with clouds, you’re not alone—the scientific community is, too. What is clear is that heightened levels of solar activity can temporarily reduce the amount of galactic cosmic rays that strike a planet’s atmosphere. Karoff and Svensmark are making the controversial claim that such cosmic rays can significantly boost cloud formation by ionizing molecules in Earth’s lower atmosphere. Thus, the narrative goes, if our faint young Sun was as active as Kappa Ceti is today, the resulting drop in cosmic-ray-induced cloud formation could explain how Earth didn’t freeze. Of course, if cosmic rays can notably affect Earthly weather and climate, it stands to reason that they would do so today—and potentially wreak havoc on climatologists’ computational models. But that’s another story.—LB


Originally published April 12, 2010

Tags neuroscience physical science research

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