Spatial distribution of cell turgor pressure, cell osmotic pressure and relative elemental growth rate were measured
in growing tall fescue leaves (Festuca arundinacea). Cell turgor pressure (measured with a pressure probe) was
c. 0.55 MPa in expanding cells but increased steeply (+0.3 MPa) in cells where elongation had stopped. However,
cell osmotic pressure (measured with a picolitre osmometer) was almost constant at 0.85 MPa throughout the leaf.
The water potential difference between the growth zone and the mature zone (0.3 MPa) was interpreted as a
growth-induced water potential gradient. This and further implications for the mechanism of growth control are
discussed.
