The short-term responses of leaf elongation to salinity are investigated in this study. The kinetics of maize (Zea mays L.) leaf elongation were measured with Linear Variable Differential Transformers (LVDTs). After exposure to salinity (0 to 120 mol m−3 NaCl), leaf elongation rates (LER) declined rapidly. Within 4 h, LER had recovered and reached a new steady-state for all salinity treatments. These rates were reduced by 10, 20, and 60% of control rates by 40, 80 and 120 mol m−3 NaCl, respectively. Osmotic adjustment in the growing zone of leaves was correlated with the recovery of LER after plant exposure to salinity. However, after 4 h of exposure, the osmolality of the cell sap continued to increase without effect on steady-state LER. Estimates of the apparent turgor in the growing zone indicated that turgor was no longer limiting LER of salt-stressed plants after 4 h. An in vivo technique was developed to apply a unidirectional force to intact growing leaves of maize to mimic increases in elongation force. Relative elongation rate (RER) were increased by adding weights to the LVDT core to increase elongation force. Plots of RER as a function of elongation force gave estimates of two growth coefficients: the yield threshold and the yielding coefficient, mL/(m + L), where m is the cell wall extensibility and L is the hydraulic conductivity. RER as a function of elongation force was determined immediately, 05, 4, and 21 h after plants were salinized. Estimates of the growth coefficients indicated that the apparent yield threshold decreased immediately after salinization. However, when LER reached steady-state, the yield threshold of salt-stressed plants had increased above control values and was the only limiting growth coefficient. There were no significant effects of salinity on the yielding coefficients, cell wall extensibility or hydraulic conductivity. One of the advantages of this in vivo technique over other methods is that yield threshold, yielding coefficient, and cell wall extensibility can be determined without the confounding effects of wounding or osmotic stress. This technique may prove widely applicable to the study of other growth regulating factors.