Effects of Micro-Nutrient Deficiencies on Growth and Vitamin Content of the Tomato

Abstract

1. An experiment was designed to test the effects of manganese, copper, zinc, molybdenum, and iron deficiencies on the ascorbic-acid, riboflavin, and provitamin-A content of tomato fruits. The criteria of a micro-nutrient deficiency included measurements of growth and fruitfulness, development of deficiency symptoms, and chemical analyses of both leaflets and fruits. All data were reduced and analyzed by statistical methods. 2. An apparatus made from Pyrex glass is described for use in micro-nutrient studies in the greenhouse when it is desired to grow plants to maturity and to test the effects of a number of treatments in replicated cultures. 3. External deficiency symptoms of vegetative parts are described for plants deficient in manganese, copper, zinc, and iron. A characteristic manganese-deficiency symptom which occurs in tomato fruits is described. A possible deficiency symptom shown by fruits with respect to zinc is also described. 4. Deficiencies of manganese, copper, zinc, and iron resulted in considerably less growth and fruitfulness than was measurable in control plants. The growth and fruitfulness of plants grown with a limited supply of molybdenum are comparable with those of control plants. 5. In general, chemical analyses of leaflets and fruits from plants grown with limited supplies of manganese, iron, zinc, and molybdenum showed significantly smaller quantities of the respective element than did the control plants. Development of the symptoms associated with a particular deficiency with respect to their position on the plant was closely correlated with the distribution of the element in the plant. The latter was determined by chemical analyses of leaflets from the top, middle, and lower thirds of the plant. 6. The ascorbic-acid content of fruits was not affected by limiting the supply of manganese, zinc, copper, and molybdenum, although growth and fruitfulness were seriously affected by a lack of manganese, zinc, and copper. Fruits from iron-deficient cultures contained 30 per cent more ascorbic acid than did control fruits on a fresh-weight basis. The quantity of fruit produced by iron-deficient plants, however, was significantly less than that of control plants. 7. Slight variations in riboflavin content of fruits could be correlated with the effect of micro-nutrient deficiencies. The magnitude of these variations was small and of no practical significance. The data show a pronounced effect on riboflavin content of variations in climatic environmental conditions such as occur with different positions in the greenhouse and with a different date of fruit maturation. 8. Provitamin-A content of the fruits was not significantly affected by a limited supply of the micro-nutrients. No significant effect of environmental factors was obtained with respect to this vitamin. 9. A discussion of the possible interpretation of these results is included.