Influence of Toxic Concentrations of Micro-Nutrient Elements in the Nutrient Medium on Vitamin Content of Turnips and Tomatoes

Abstract

1. Experiments were designed in 1943 to measure the effects of high concentrations of manganese, boron, zinc, molybdenum, copper, or iron in the nutrient medium on the vitamin content of turnip greens and tomatoes grown in sand cultures. Growth data as well as results of selected mineral analyses are presented, and nutritive values in terms of thiamine, niacin, riboflavin, and ascorbic acid content are considered. 2. As the iron concentration in the nutrient medium was increased to 147 p.p.m., no significant effects on the growth of either turnips or tomatoes were evident. Both plants, however, absorbed and accumulated more iron than the controls as a result of treatment, but no significant differences in vitamin content were observed. 3. As the concentration of copper, manganese, boron, zinc, or molybdenum was increased in the nutrient medium, the growth of both turnips and tomatoes was significantly retarded. Definite and specific toxicity symptoms developed, and, invariably, as the supply of any of the micro-nutrient elements used was increased, a greater concentration of that element was found in the vegetative plant parts. 4. Certain significant changes in vitamin content were striking. For instance, as the boron supply to turnip plants was increased, a 60% increase in both niacin and thiamine concentration in leaves occurred. Ascorbic acid values, however, were 20% less. A 35% increase in both niacin and riboflavin values was associated with increased manganese supply. In this instance, ascorbic acid values were 25% less. In tomatoes a 60% increase in ascorbic acid content of the fruit was associated with relatively high copper concentrations in the nutrient solution. Ascorbic acid values were significantly less than in control fruits, however, as the concentration of boron, manganese, or molybdenum was increased in the nutrient. 5. Some practical as well as theoretical connotations of these results are discussed. The reports that manganese fertilization of the soil results in high ascorbic acid values are considered in relation to these results which indicate that manganese supply to the plant has little influence on ascorbic acid content.