Kinetics of Root Elongation of Maize in Response to Short-Term Exposure to NaCl and Elevated Calcium Concentration

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Abstract
To study the effect of salt (NaCl) on root elongation we developed a device that measures this effect by means of a Linear Variable Differential Transformer (LVDT). To test the efficacy of the device we performed experiments demonstrating that (a) rates of elongation of primary maize (Zea mays L.) roots were comparable to elongation rates of primary roots growing freely in solution culture; and (b) chilling and low O2 concentrations of the solution elicited the expected responses. Inhibition of root elongation by 75 mol m−3 NaCl was gradual. At an iso-osmotic concentration, mannitol did not inhibit root growth, suggesting that the inhibition was not due to osmotic factors but rather to effects of salt on metabolism. The addition of supplemental Ca (10 mol m−3) ameliorated this stressful condition. Timing of the application of Ca was critical. Treatment with Ca after addition of NaCl only partially restored growth, but pretreatment with Ca completely prevented the inhibition of growth by salt stress.