The use of the electrolyte leakage method for assessing cell membrane stability as a water stress tolerance test in durum wheat

This work was carried out to adapt the electrolyte leakage technique to durum wheat and then to evaluate its relevance in the assessment of the cell membrane stability as a mechanism of water stress tolerance in this species. The method currently used is based on in vitro desiccation of leaf tissues by a solution of polyethylene glycol (PEG) and a subsequent measurement of electrolyte leakage into deionised water. It consists of three successive steps: (1) a washing treatment to remove solutes from both leaf surfaces and cells damaged by cutting; (2) a stress period during which the leaf tissues are plunged in a PEG-solution and (3) a rehydration period during which after-effects of the stress are evaluated. During the washing period, the major part of electrolytes was removed within 15 min. Varying the stress conditions influenced both the percent and the kinetics of electrolyte leakage during rehydration. Electrolyte leakage exhibited a characteristic pattern reflecting the condition of cellular membranes (repair and hardening). In practice, we recommend a 15-minute washing time, a 10-hour stress period and 4 h of rehydration. The extent of the cell membrane damage not only correlated well with the growth responses of wheat seedlings belonging to various cultivars to withholding water but also with the recognised field performances of these cultivars. The relative proportion of endogenous ions lost in the effusate during the rehydration step may vary strongly according to the element analysed and the precise nutritional status of the plant should therefore be considered. However, an increase in inorganic ion leakage does not fully explain the recorded PEG-induced increase in electrical conductivity (EC) during the subsequent rehydration step and organic ions are probably also involved in such an increase.