ABSTRACT Plant hormones regulate many aspects of plant growth and development. Both auxin and cytokinin have
been known for a long time to act either synergistically or antagonistically to control several significant developmental
processes, such as the formation and maintenance of meristem. Over the past few years, exciting progress has been made
to reveal the molecular mechanisms underlying the auxin–cytokinin action and interaction. In this review, we shall briefly
discuss the major progress made in auxin and cytokinin biosynthesis, auxin transport, and auxin and cytokinin signaling.
The frameworks for the complicated interaction of these two hormones in the control of shoot apical meristem and root
apical meristem formation as well as their roles in in vitro organ regeneration are the major focus of this review.