Genetic and environmental regulation of root growth and development

Roots of vascular plants serve important functions in anchorage and the acquisition of nutrients and water from soil. Root systems continuously adjust their architectural, physiological, and metabolic performance to adapt to alterations of their biotic and abiotic environment. In this chapter, we highlight the current knowledge of the genetic control and molecular regulation of the formation and function of individual root types and whole root systems. We summarize the role of phytohormone homeostasis and the effects of environmental signals, such as nutrient and water availability as well as soil physical and chemical factors, on root development. In addition, we discuss alterations of root morphology and architecture during the interaction with beneficial microbes, such as plant growth–promoting rhizobacteria and arbuscular mycorrhizal fungi, and illustrate the importance of phytohormone production and signaling crosstalk between microorganisms and plant roots. The chapter concludes with a special emphasis on the phytohormone auxin as the key biological molecule mediating growth and development of the root system and root responses to environmental variables.