Going underground: The importance of soil heterogeneity in shaping plant productivity and responses to saline soils

Plants have to cope and respond to an ever-changing environment, including in soils. Their performance thus depends on their ability to perceive changes in the root zone and to adapt by altering resource allocation to growth, reproduction, or defense. With the majority of physiological and molecular research adopting a reductionist approach, which oversimplifies salinity as a single and uniform factor, conclusions drawn from these studies are likely to have underestimated the complex interactions that shape plant responses in field conditions. In this viewpoint, we argue that understanding root (and whole-plant) responses to soil heterogeneity, intended as the results of dynamic and multiple jointly acting abiotic stressors in saline environments, is central to salinity research. In particular, we introduce a conceptual agenda for studying roots under the dynamic and heterogeneous conditions found at the soil–root interface in saline soils, and its potential to provide new knowledge on how to deal with and adapt in a saltier world, with benefits for agriculture and natural resource management. • Salinity is generally oversimplified as a single and uniform stressor • At the root level, heterogeneity at finer scales remains underexplored • Rhizosphere microbial assemblage boost root foraging abilities in heterogeneous soils • Salt tolerance and avoidance depends on root plasticity to exploit heterogeneity