Cool Job: Rethinking how plants hunt for water | Science News for Students

Cool Job: Rethinking how plants hunt for water

Researcher probes the very beginnings of root growth
Oct 11, 2017 — 7:00 am EST
José Dinneny

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

root branch
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.

glow roots
 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.

Power Words

(for more about Power Words, click here)

academic     Relating to school, classes or things taught by teachers in formal institutes of learning (such as a college).

accountant     A person whose job it is to develop, manage or inspect financial records.

alien     A non-native organism. (in astronomy) Life on or from a distant world.

biology     The study of living things. The scientists who study them are known as biologists.

bond     (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

climate     The weather conditions that typically exist in one area, in general, or over a long period.

climate change     Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

colleague     Someone who works with another; a co-worker or team member.

development     (in biology) The growth of an organism from conception through adulthood, often undergoing changes in chemistry, size and sometimes even shape.

DNA     (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).

exotic     An adjective to describe something that is highly unusual, strange or foreign (such as exotic plants).

extraterrestrial     (ET) Anything of or from regions beyond Earth.

gene     (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

genetic     Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics. People who work in this field are geneticists.

hormone     (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

inherent     An adjective that describes some trait or condition that is always present in something or is a critical feature of it.

lateral     An adjective for something that occurs on or to the side of something.

micrometer     (sometimes called a micron) One thousandth of a millimeter, or one millionth of a meter. It’s also equivalent to a few one-hundred-thousandths of an inch.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nervous system     The network of nerve cells and fibers that transmits signals between parts of the body.

petri dish     A shallow, circular dish used to grow bacteria or other microorganisms.

PhD     (also known as a doctorate) A type of advanced degree offered by universities — typically after five or six years of study — for work that creates new knowledge. People qualify to begin this type of graduate study only after having first completed a college degree (a program that typically takes four years of study).

population     (in biology) A group of individuals from the same species that lives in the same area.

Proceedings of the National Academy of Sciences     A prestigious journal publishing original scientific research, begun in 1914. The journal's content spans the biological, physical, and social sciences. Each of the more than 3,000 papers it publishes each year, now, are not only peer reviewed but also approved by a member of the U.S. National Academy of Sciences.

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

seedling     The initial plant that sprouts leaves and roots after emerging from a seed.

solar system     The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

stress     (in biology) A factor — such as unusual temperatures, movements, moisture or pollution — that affects the health of a species or ecosystem.

tissue     Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

trait     A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.

Citation

Journal:​ ​​Y. Bao et al. Plant roots use a patterning mechanism to position lateral root branches toward available water. Proceedings of the National Academy of Sciences. Vol. 111, June 24, 2014, p. 9319. doi: 10.1073/pnas.1400966111.

Journal:​ D. Dietrich et al. Root hydrotropism is controlled via a cortex-specific growth mechanism. Nature Plants. Vol. 3, May 8, 2017, 17057. doi: 10.1038/nplants.2017.57.