Subterranean space exploration: the development of root system architecture

The colonisation of terrestrial environments offered plants a host of advantages. It also presented them with major challenges. The foremost amongst these, the dichotomous nature of terrestrial environments, was clearly successfully met by the development of an integrated but divergent root–shoot structure. Whereas they share many similarities, roots and shoots evolved specialist functions in line with their principle roles and their growth environment. In this review, we discuss a number of areas where recent discoveries, principally in Arabidopsis, are shedding light on the mechanisms that enable the successful colonisation of the soil environment.

► Regulatory balanced antagonism between auxin and cytokinin.
► Lateral root initiation triggered by internal clock.
► Root system architecture modified by NH4+, NO3− and Pi, through auxin signalling.