Physiological Mechanisms of Solanum tuberosum L. Plants' Tolerance to Chloride Salinity

The mechanisms of potato (Solanum tuberosum L.) plants' tolerance to chloride salinity were investigated in cv. Lugovskoi regionalized in Russia. Regenerated plants were produced in vitro from apical meristem and grown on half-strength Murashige and Skoog medium (0.5 MS) using a hydroponic unit in controlled-climate conditions. At the age of six weeks, the plants were exposed to salt stress (50-150 mM NaCl, 7 days). Plant response to salt stress was estimated by growth parameters (fresh and dry biomass of the aboveground and underground parts of plants, linear dimensions of shoot and root, area of leaf surface, and number of stolons) and physiological characteristics (level of photosynthetic pigments, accumulation of sodium, potassium, and calcium ions in the aboveground and underground parts of plants, content of proline, activity of antioxidant enzymes, plant tissue hydration, osmotic potential, and POL). It was found that, in response to salinity, the plants of potato, cv. Lugovskoi, showed a considerable inhibition of growth processes, reduction in chlorophyll a content, and suppression of stolon formation, which points to a rather low salinity tolerance of the cultivar. At the same time, under weak or moderate salt stress, the plants preserved water homeostasis owing to effective osmoregulation, actively accumulated proline that acted as a stress protector, and showed hardly any signs of oxidative stress. It was assumed that low salt tolerance of this cultivar depends on the inability of its root system to retain sodium ions and ensure selective ion transport to the aboveground part of the plant and on inefficiency of the system of sodium ions' removal from the cytoplasm of leaf cells and their compartmentalization in the central vacuole with the purpose of reducing their toxic effect. The obtained results may be useful for working out a technique of improving salt tolerance of this cultivar by the methods of molecular genetics.