A Novel Mechanism for Enhancing Root Growth in Response to Drought

Researchers have learned how drought causes plants to modify their root systems and grow deeper into the ground to reach water reserves.

The University of Nottingham's plant scientists, working with Shanghai Jiao Tong University, have determined how the plant hormone abscisic acid (ABA), which is known to play a part in drought response, affects the angles at which roots grow in cereal crops like maize and rice. The study was published in the journal Current Biology.

The study demonstrates how auxin, another important hormone, and ABA cooperate to influence the root growth angle, offering a possible method for creating drought-tolerant crops with better root system architecture.

Improving crops' resistance to water scarcity is essential because drought is a serious threat to the world's food security. Over the past 10 years, drought—a significant abiotic stressor—has resulted in significant losses in crop production of about $30 billion. Global drought conditions have gotten worse due to climate change, especially global warming. With a population of 10 billion people expected by 2050 and significant freshwater depletion, it is critical to develop crops that can withstand drought.

Plant root systems, the primary organs responsible for soil interaction, play a crucial role in actively seeking water resources. During drought conditions, water frequently evaporates from the topsoil, leaving it depleted and rendering water accessible only in the deeper subsurface layers.

Plants rely on abscisic acid (ABA), a crucial plant hormone, to effectively adapt to these challenging circumstances. This groundbreaking research provides valuable insights into the precise mechanisms by which ABA influences root growth angles, enabling plants to delve deeper into the subsoil in their quest for water.

The researchers found a novel mechanism in which auxin production is stimulated by ABA, leading to increased root gravitropism and the ability to grow at steeper angles in response to drought. Studies revealed that, in comparison to normal plants, plants with genetic mutations that prevent the production of ABA had shallower root angles and a weaker reaction to gravity when they bent.

Lower levels of auxin in their roots were associated with these defects. Auxin is essential to this process, as demonstrated by the researchers' restoration of normal root growth in these mutants by externally adding auxin.

The results were consistent between maize and rice, indicating that this mechanism may also affect other cereal crops.

Finding ways to tackle food insecurity is vital and the more we understand the mechanisms that control plant growth, the closer we are to designing systems to help plants to do this and improve crop yields during droughts.”

Dr. Rahul Bhosal, Associate Professor, School of Biosciences, University of Nottingham