Cool Job: Rethinking how plants hunt for water

Researcher probes the very beginnings of root growth

José Dinneny studies how plants grow under stress. What he learns could help to feed Earth’s growing population.

Robin Kempster

José Dinneny wants us to see plants as strange.

They have no brain and no nervous system. Yet they take in different kinds of information and can make good decisions. Plants also find water without sight or touch.

They are everywhere in our lives: lawns, salads and pots on a sunny windowsill.  They’re so familiar it’s easy to forget how odd they really are.

“We’re out searching the solar system and the galaxy for extraterrestrial life,” says Dinneny. Yet, he argues, “We have aliens on our own planet.”

Dinneny is a plant biologist at the Carnegie Institution for Science in Stanford, Calif. He says the thrill of discovering plants’ alien ways drives him to explore how roots search for water. His research group “runs on curiosity,” he says.

He conducts projects just to discover how plants work. What he learns, though, could be useful in finding better ways to grow food. He started his career studying details of how plants develop their parts and shapes. With that background, he’s now interested in how the roots of plants hunt for water.

These questions are important in “this huge crisis we face as a species,” says Jonathan Lynch. He is a root biologist at Pennsylvania State University, in University Park, and the University of Nottingham in England. The human population is growing — and fast. Whether farmers will be able to boost their crops and keep up is huge question. And Earth’s changing climate only makes this more complicated.

A pivotal moment

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This is a cross section of a rice root. The root has formed a branch poking out to search for water. This is just one of the many tiny directional choices that will determine whether a plant can find what it needs to survive.Pooja Aggarwal

In a different world, Dinneny says, his job might have been cooking plants instead of studying them. He makes “a mean pot pie,” he claims. Plus, he relishes the nightly challenge of putting together a dinner his three children will eat without coaxing.

He’s not the first guy in his family to take to the stove. In the 1950s, his mother’s dad was cooking at a resort in Acapulco, Mexico. What he dished out impressed one guest in particular. That diner hired his grandparents as an at-home cook and a maid. That meant a move to southern California. Eventually his grandfather became a chef in a Los Angeles restaurant.

Dinneny spent much of his childhood in California’s San Fernando Valley. “I was placed in classes that weren’t particularly challenging.” The school he went to had a high dropout rate. In 10th grade, though, he took an Advanced Placement biology class. Suddenly, things changed.

He still remembers a pivotal moment when his teacher asked about a chemical bond in DNA. “I was the only person who raised his hand.” The answer: a phosphodiester (FOS-foh-dy-ES-tur) bond. “Everyone looked around the room sort of wondering who could possibly have known that factoid,” he remembers.

He even surprised himself. Dinneny began to realize he had a talent for understanding biology. He lobbied hard to transfer to advanced classes. He began to apply himself to studying. Dinneny didn’t come from an academic family, but he had fine examples of working hard. That included his mother. She raised him as a single mom working as a government accountant.

“Often we kind of cubbyhole ourselves into, ‘OK, I’m good at this,’ or ‘I’m not good at that.’ Or they’re doing well because they’re just inherently better at doing this than I am,’” he says. “There is a magical relationship between effort and success.” Not every goal gets met, but “you’re going to do better than you ever thought.”

By his final year of high school, Dinneny was a straight-A student, and he went to University of California, Berkeley. There, plant science captivated him. For his PhD, he went to the University of California, San Diego. He studied the genetics of plant development. Later, he studied plants trying to grow in difficult places. Now he’s focusing on ways to figure out what’s happening in roots.

Watching roots glow

To study how plants grow those roots, biologists often start seedlings in petri dishes with a nutrient gel instead of soil. This lets researchers experiment with lots of plants in the lab. But this is very different from how plants grow in real life. For more realism, Dinneny and his colleagues created a system called GLO-Roots. It creates a special view of roots in soil.

In the GLO-roots system, plants grow their roots in slim sandwiches of soil held between two clear plates. The roots weave among air pockets, micro rivers and clots of dirt. It’s like mini versions of the conditions that roots find in the ground. But these roots are special: They glow when various genes turn on in this twinkling underground observatory. Computers analyze where that glow shows up. And that gives researchers clues to how roots are responding to their environment.

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A setup called GLO-roots allows researchers to visualize how the roots of a seedling explore the soil. This view combines daily images, starting 11 days after sowing a seed. The closer the coloration gets to white, the more recently the little rootlets formed. R. Rellán-Álvarez et al/eLIFE 2015

Thrusting out a side branch to seek out water depends on local soil conditions, Dinneny and his colleagues learned. Analyzing hormones showed that the roots’ tissues can sense water differences at points only about 100 micrometers (around a thousandth of an inch) apart. Dinneny calls this “hydropatterning.” His team described this trait in a 2014 paper in the Proceedings of the National Academy of Sciences.

Side roots that branch out toward water may be familiar. Yet it’s another strange facet of plant life. For vertebrates, body parts form on babies developing in protected spaces. Egg shells or mothers’ bodies can screen out many outside influences. Cues from soil water, however, change where the little nubbin of a side root forms. For plants, it’s as if the number of mouths on an unborn baby’s head changed if there was more food outside.

“Myself and many other people had studied lateral roots for many years,” says Malcolm Bennett. He is a plant biologist at the University of Nottingham in England. He, too, worked on this study. It was familiar to see seedlings in petri dishes forming roots mostly on the wet side. But Dinneny thought to ask how something so familiar was actually happening.

For much of his childhood, Dinneny was captivated by deep-sea creatures and ocean exploring. But plants, it seems, have turned out to be strange enough.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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