Sodium as an Essential Micronutrient Element for a Higher Plant (A triplex vesicaria)

Abstract

Methods are described by which plants were grown under conditions of Na depletion. Culture solutions prepared from purified salts contained less than 0.07 [mu]eq/ liter (0.0016 ppm) of Na as an impurity and water contained less than 0.0087 [mu]eq/ liter (0.0002 ppm) of Na. Cultures were protected from atmospheric contamination by Na in a small greenhouse maintained at a slightly positive pressure by a continuous supply of filtered air. Under these conditions it was not possible to detect any increase in the amount of Na in a culture or its plants over the period of an experiment. Characteristic deficiency symptoms developed about the 20th day in A. vesicaria (bladder saltbush) plants which had not received an application of Na to their cultures. Leaves became chlorotic and developed necrotic patches at their tips and along their margins, after which little further growth was made. By about the 35th day some plants died. Plants receiving 0.02 meq/ liter (0.46 ppm) Na2SO4 made favorable growth, and when harvested on the 48th day had approximately 10 times the dry weight of plants which had not received Na. Plants which had developed severe symptoms of Na deficiency recovered within about 7 days of receiving an application of Na to their culture solutions. Only Na of the group 1 elements effected the recovery of Na-deficient plants of A. vesicaria. Plants receiving equivalent amounts of Li, K, and Rb in their cultures could not be distinguished from those to which no addition of Na had been made. It is concluded that small amounts of Na are essential for the growth and development of A. vesicaria.