INTERACTIVE EFFECTS OF SALINITY AND CALCIUM ON HYDRAULIC CONDUCTIVITY, OSMOTIC ADJUSTMENT, AND GROWTH IN PRIMARY ROOTS OF MAIZE SEEDLINGS

Abstract

ABSTRACT Increasing the calcium ion activity in salinized root media has often been shown to ameliorate the inhibitory effect of salinity on plant growth. In order to better define the biophysical mechanisms involved in these growth responses, we investigated the interactive effects of salinity and calcium on hydraulic conductivities and osmotic potential gradients in roots of maize seedlings. The length of the primary roots was reduced by 54% after 4 days of growth in 0.1-strength Hoagland solution salinized with 100 mM NaCl and by 20% when 10 mM calcium was also added to the salinized root medium. Roots showed 69% osmotic adjustment in response to salinization, with or without extra calcium in the root medium. The mean hydraulic conductivity, L, of the apical 4 cm of maize seedling roots was determined by assaying osmotically-induced backflow. The assay was sensitive enough to detect reductions in L induced by lowering the assay temperature from 27 to 14°C. These reductions in L exceeded those caused by...