Root hydraulics in salt-stressed wheat

The aim of the present study was to test whether salinity, which can impact through its osmotic stress component on the ability of plants to take up water, affects root water transport properties (hydraulic conductivity) in bread wheat (Triticum aestivum L). Hydroponically grown plants were exposed to 100 mM NaCl when they were 10-11 days old. Plants were analysed during the vegetative stage of development when they were 15-17 days old and the root system consisted entirely of seminal roots, and when they were 22-24 days old, by which time adventitious roots had developed. Root hydraulic conductivity (Lp) was determined through exudation experiments (osmotic Lp) on individual roots and the entire plant root system, and through experiments involving intact, transpiring plants (hydrostatic Lp). Salt stress caused a general reduction (40-80%) in Lp, irrespective of whether individual seminal and adventitious roots, entire root systems or intact, transpiring plants were analysed. Osmotic and hydrostatic Lp were in the same range. The data suggest that most radial root water uptake in wheat grown in the presence and absence of NaCl occurs along a pathway that involves the crossing of membranes. As wheat plants develop, a nonmembraneous (apoplast) pathway contributes increasingly to radial water uptake in control but not in NaCl-stressed plants.