Review: Acid growth, an ongoing trip

Plant growth is determined not only by cell division, but also by loosening of the cell wall. Arsuffi and Braybrook review our understanding of the mechanisms of cell wall loosening. Already in the 1970s scientists started to observe that low pH leads to increased growth, using destructive experiments. Although the effect of pH enhanced extensibility of effectively dead organs, RNA and protein synthesis were later identified to be important for effective cell wall loosening. Today we know that auxin induces apoplast acidification through phosphorylation of proton pumps at the plasma membrane. Modern fluorescent pH probes allow identification of the differences in apoplast acidification dynamics between hypocotyl and root during their growth. In the future, differences between species, feedback mechanisms and other wall modifying agents remain to be identified for their role in apoplast acidification and growth regulation. (Summary by Magdalena Julkowska) J. Exp. Bot 10.1093/jxb/erx390