Unearthing Root Response Mechanisms to Soil Compaction in Legumes

Roots are essential for the survival and functioning of plants, serving as anchors in the soil and drawing in vital nutrients and water. Roots also engage in diverse microbial interactions, including pathogenic interactions that cause plant disease and non-pathogenic interactions, such as symbiotic and commensal relationships. Mechanical resistance in compacted soil is one of the biggest challenges for root exploration. Soil compaction hampers plant growth by restricting root elongation, reducing root proliferation, and limiting access to water, nutrients, and oxygen. These restrictions interfere with root-microbe interactions and also impair aboveground growth, leading to decreased shoot biomass, stunted development, and lower overall productivity. Legume roots form symbiotic relationships with soil-dwelling Rhizobium, resulting in root nodules that convert atmospheric nitrogen (N) into ammonia, thereby promoting plant growth. However, the impact of soil compaction on legume roots remains poorly studied. In this review, we examine key adaptive strategies used by legume roots to counteract soil compaction, focusing on the underlying molecular pathways. A complex signalling network regulates molecular processes that control root development and nodulation in legumes. We also explore the genetic and environmental factors that influence morphological, anatomical, and biochemical traits under mechanical stress, providing insights for improving stress resilience in legumes.