Ca and pH as integrating signals in transport control

Plant transporters are often placed in the context of the functional machinery that maintains the plant. For example, K + channels are essential for regulating membrane potential and for K + nutrition, and sucrose transporters are part of the symplastic photosynthate highway. However, it is becoming increasingly clear that, in addition to these ‘maintenance ’ functions, transporters are essential elements of environmental sensing, response and developmental control within the plant body. Our understanding of these regulatory roles has advanced considerably in the last 5 years with the advent of genomic tools that are allowing us to define these transport activities at the molecular level. In this chapter, we will explore the themes of how transporters are involved in developmental processes and control and how environmental signals are processed through transport phenomena.