Objectives Root growth and rhizosphere interactions are key factors that affect soil nutrient uptake by plant. Roots can fully exert morphological plasticity, change root configuration and expand the contact area with soil to obtain essential nutrients by interpenetrating growth in the structured soil. Moreover, the physiological plasticity of root system, together with its morphological plasticity, can significantly affect and regulate rhizosphere interactions, which may provide the possibility and potential strategies for plants to obtain soil nutrients more efficiently and effectively. Exploring the possible mechanisms to effectively regulate root morphology and physiological plasticity, maximizing rhizosphere processes and strengthening rhizosphere interactions in intensive agriculture systems are of great theoretical and practical importance to improve crop nutrient use efficiency and increase crop yield in a sustainable way.

Major advances Melatonin as a new signal molecule of plant growth regulation, shows a positive regulatory effect on plant growth and increases tolerance to salt, drought, low temperature, and other abiotic stresses. Melatonin also has a significant regulatory effect on root growth. Melatonin inhabits plant primary roots, whereas it shows a concentration dependence regulation on the development and growth of lateral roots and adventitious roots, thus indicating a profound impact on the root configuration. Although the mechanism of melatonin regulation of root growth is not clear at present, it is speculated that melatonin affects the transport of photosynthetic products and sugar signals, so as to regulate the distribution of carbon flow and root growth in the soil by regulating photoperiod. Meanwhile, melatonin can also be interoperable with plant hormones such as auxin, and participate in the signaling pathway of hormone regulation of plant growth, which has an effect on plant growth, development and metabolism. These new findings provide an important theoretical basis for further revealing the mechanism of melatonin regulation of root growth and development.

Suggestions and expectations Root growth and architecture significantly affect rhizosphere processes and rhizosphere interactions. Melatonin, as a regulatory factor, has a significant effect on root morphological plasticity. However, the roles of melatonin in rhizosphere processes and interactions remain largely unclear, and related research is still relatively lacking. Revealing its mechanisms in rhizosphere interactions and understanding its role in regulating root growth and rhizosphere processes could provide the important scientific basis for precisely regulating crop growth, strengthening the rhizosphere interactions, and thus improving the efficient use of nutrients in the intensive cropping systems.