The biophysics of differential growth.

The intrinsic control of uniform and differential growth of plant cells can be traced to a small number of physical parameters. These are cell wall rheology, membrane and tissue hydraulic conductivity, and membrane and tissue solute transport. Water and solute effects are manifested as alterations in turgor pressure. Environmental and biochemical processes always channel their effects through one or more of these parameters. Technical developments such as the pressure probe and Instron tensiometer, together with a reappraisal of older techniques, are beginning to allow assessment of the relative roles of these factors. Although the importance of cell wall rheology is becoming increasingly apparent, there is still insufficient information to allow generalized conclusions regarding the role of turgor pressure in differential growth. This review considers attempts to correlate these parameters with observed anatomical growth patterns.