Why Measure Osmotic Adjustment?

TLDR

Osmotic adjustment is widely viewed as a drought or salinity adaptation that maintains turgor and supposedly boosts growth or yield, yet evidence shows it diverts essential solutes, does not control cell expansion or stomatal conductance, and its impact on yields remains largely unexplored. Future research should test hypotheses rather than merely measure osmotic adjustment.

Abstract

Osmotic adjustment (erroneously called 'osmoregulation') is generally regarded as an important adaptation to drought or salinity. Because it helps to maintain turgor and cell volume, it is often thought to promote growth, yield, or survival, of plants in dry or saline soils. However, a physiological rationale for such views is lacking. Osmotic adjustment itself cannot promote growth; the solutes which account for it must be diverted from essential processes such as protein and cell wall synthesis. Further, it now appears that turgor does not control cell expansion or stomatal conductance. Thus, osmotic adjustment cannot affect yields except via other processes, the controls of which are almost entirely unexplored. Future research in this area should test hypotheses, rather than merely measure osmotic adjustment.