Roots are plant organs that anchor the plant by absorbing water and nutrients from the soil and storing carbohydrates. They lack specialized structures or sensory cells that allow them to detect or measure heat directly.
Plant roots have their own thermometer that they use to gauge the temperature of the soil around them and adjust their growth accordingly. A team led by Martin Luther University Halle-Wittenberg (MLU) was able to demonstrate that roots have their own temperature sensing and response system through extensive experiments. The researchers also provide a new explanation for how roots detect and respond to higher temperatures in a new study published in The EMBO Journal. The findings could aid in the development of new approaches to plant breeding.
Climate chambers were used by the researchers to study how the plant model organism thale cress, as well as the crops cabbage and tomatoes, react to rising ambient temperatures. They raised the temperature in the room from 20 to 28 degrees Celsius (68 to 82.4 degrees Fahrenheit).
We discovered that the roots were unaffected by this and grew at high temperatures in the same way that plants with intact shoots did. The higher the temperature, the more cell division there was, and the roots grew significantly longer.
Professor Marcel Quint
“Until now, it was assumed that the plant shoot controlled the entire process and acted as a long-distance transmitter signaling to the root that it should alter its growth,” says Professor Marcel Quint of MLU’s Institute of Agricultural and Nutritional Sciences. Through extensive experiments conducted in collaboration with researchers from the Leibniz Institute of Plant Biochemistry (IPB), ETH Zurich, and the Max Planck Institute for Plant Breeding Research in Cologne, his team was able to disprove this. In one experiment, scientists removed the plant’s shoot but allowed the roots to grow.
“We discovered that the roots were unaffected by this and grew at high temperatures in the same way that plants with intact shoots did. The higher the temperature, the more cell division there was, and the roots grew significantly longer,” Quint says.
The researchers also used mutant plants whose shoots were unable to detect or respond to higher temperatures. Those were grafted onto roots that did not have this flaw. Even though the shoot did nothing, the roots were able to respond to the heat in the soil.
The researchers discovered that root cells increased the production of the growth hormone auxin, which was then transported to the root tips in all of their experiments. It stimulated cell division and allowed the roots to reach deeper into the soil. “Because heat and drought usually occur in tandem, it makes sense for the plants to tap into deeper and cooler soil layers that contain water,” Quint explains.
For a long time, scientists have known how plant shoots react to higher temperatures. Their cells also produce more auxin, but the plant reacts differently than its roots. The cells in the shoot stretch, the stalk grows taller, and the leaves become narrower and farther apart.
The research also offers new insights into plant breeding. “With climate change, root growth is becoming increasingly important for breeding.” “Understanding the molecular basis for temperature-dependent root growth may aid in effectively equipping plants against drought stress and achieving stable yields over time,” says Quint. Quint’s research team will continue to work in this area in the coming years. The Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) recently awarded him around 500,000 euros for a new research project on this very topic.
