Differential growth regulation in plants--the acid growth balloon theory.

'To grow or not to grow' is a central question in developmental biology and is nowadays tackled wonderfully by cell-biological approaches in various species. The rigid plant cell wall is a neat evolutionary invention for sessile organisms, which require form stability in the face of an ever-changing natural environment. However, this cellular packaging places special constrains on mechanisms that guide cellular growth. Considering the largely non-reversible, man-made environmental changes and our dependency on plant products, further insights into plant-specific growth regulation are highly desirable. Here we provide our personal, current view on cellular growth regulation in plants, highlighting the mutual importance of extra- and intracellular processes.