Plant cells are surrounded by an intricately structured protective coat called the cell wall. It’s built of cellulose microfibrils intertwined with polysaccharides like hemicellulose or pectin. We have known what plant cells look like without their walls, and we know what they look like when the walls are fully assembled, but we’ve never seen the wall-building process in action. “We knew the starting point and the finishing point, but had no idea what happens in between,” says Eric Lam, a plant biologist at Rutgers University. He’s a co-author of the study that caught wall-building plant cells in action for the first time. And once we saw how the cell wall building worked, it looked nothing like how we drew that in biology handbooks.

Camera-shy builders

Plant cells without walls, known as protoplasts, are very fragile, and it has been difficult to keep them alive under a microscope for the several hours needed for them to build walls. Plant cells are also very light-sensitive, and most microscopy techniques require pointing a strong light source at them to get good imagery.

Then there was the issue of tracking their progress. “Cellulose is not fluorescent, so you can’t see it with traditional microscopy,” says Shishir Chundawat, a biologist at Rutgers. “That was one of the biggest issues in the past.” The only way you can see it is if you attach a fluorescent marker to it. Unfortunately, the markers typically used to label cellulose were either bound to other compounds or were toxic to the plant cells. Given their fragility and light sensitivity, the cells simply couldn’t survive very long with toxic markers as well.

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Bonobos, great apes related to us and chimpanzees that live in the Republic of Congo, communicate with vocal calls including peeps, hoots, yelps, grunts, and whistles. Now, a team of Swiss scientists led by Melissa Berthet, an evolutionary anthropologist at the University of Zurich, discovered bonobos can combine these basic sounds into larger semantic structures. In these communications, meaning is something more than just a sum of individual calls—a trait known as non-trivial compositionality, which we once thought was uniquely human.

To do this, Berthet and her colleagues built a database of 700 bonobo calls and deciphered them using methods drawn from distributional semantics, the methodology we’ve relied on in reconstructing long-lost languages like Etruscan or Rongorongo. For the first time, we have a glimpse into what bonobos mean when they call to each other in the wild.

Context is everything

The key idea behind distributional semantics is that when words appear in similar contexts, they tend to have similar meanings. To decipher an unknown language, you need to collect a large corpus of words and turn those words into vectors—mathematical representations that let you place them in a multidimensional semantic space. The second thing you need is context data, which tells you the circumstances in which these words were used (that gets vectorized, too). When you map your word vectors onto context vectors in this multidimensional space, what usually happens is that words with similar meaning end up close to each other. Berthet and her colleagues wanted to apply the same trick to bonobos’ calls. That seemed straightforward at first glance, but proved painfully hard to execute.

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