In Vitro Assessment of Abiotic Stress in Date Palm: Salinity and Drought.

Date palm is one of the major crops growing in regions where abiotic stress conditions are extreme. Abiotic stress affects plant growth, development, physiology, and biochemical processes. This chapter describes a protocol to evaluate the response of date palm cultures to abiotic stresses. Tolerance to salinity stress is assessed using calcium chloride (CaCl2 ), potassium chloride (KCl), and sodium chloride (NaCl) at 11.96, 12.06, and 9.45 g/L, respectively (equivalent to 0.8 MPa osmotic potential), with different exposure durations (1-12 days). Polyethylene glycol (PEG 8000) is tested at 0-30% (w/v) to assess tolerance to drought stress. Techniques are described to define the effects of these stress agents on the growth of callus and cell suspension cultures, water content, proline accumulation, and Na+ and K+ content ratio, in addition to the technique used for determining the median lethal dose (LD50 ) for PEG (29.5%) and NaCl (11.54 g/L). This protocol will be useful for future studies of in vitro selection of tolerant cell lines.