Composition of the Tomato Plant as Influenced by Nutrient Supply, in Relation to Fruiting

1. Tomato plants were grown through the fruiting stage under greenhouse conditions in soil, sand, and large-scale water cultures, with nutrient solutions of varying composition. 2. The composition of the fruit with respect to constituents derived through absorption by roots was, in contrast to the modifiable composition of foliage, on the whole little affected by the kind of nutrient medium in which the plants grew. The composition was also not found to be materially altered in water-culture experiments in which the total concentration and relative proportions of nutrients were varied. Marked reduction was found in the potassium or phosphorus content of fruit developed on plants grown in a potassium- or phosphorus-deficient nutrient solution. 3. On a percentage dry-weight basis the concentration of potassium, calcium, magnesium, phosphorus, and nitrogen was markedly lower in the fruit than in the leaf, and the relative proportions of these nutrients were strikingly altered. 4. The manual removal of flowers in plants grown in a complete nutrient solution resulted in distinct alterations in growth, shown by thickening of stems and leaves, proliferation of new growing points at the leaf axils, and emergence on the stem of rootlike structures. Defloration was found to be associated with marked accumulation of starch in all tissues and of sugars and organic nitrogen in the stems and petioles. However, defloration was not found to influence materially the composition of foliage with respect to phosphorus, calcium, or magnesium. The potassium content of the petioles was higher in the fruitful plants, but no marked difference was found in the potassium content of leaf blades. 5. Defloration of plants kept in a potassium-deficient nutrient solution delayed the onset of potassium-deficiency symptoms and was associated with a higher potassium content in the young leaves of the deflowered than in the fruitful plants. The otherwise low potassium content of leaves showed an increasing upward gradient as contrasted with a downward gradient in plants grown in a complete nutrient solution. Downward calcium and magnesium gradients found in plants grown in complete nutrient were also found in leaves of potassium-deficient plants, but the latter had a higher content of these elements in the fruitful than in the deflowered plants. 6. Defloration of plants kept in a phosphorus-deficient nutrient solution delayed the onset of phosphorus-deficiency symptoms and was associated with a higher phosphorus content in the young leaves of the deflowered plants. The otherwise low phosphorus content of leaves from all phosphorus-deficient plants, whether fruitful or deflowered, showed-in contrast with the control plants-increasing upward gradient. 7. Several general considerations are given on the relation of the external nutrient supply and fruiting to the distribution of nutrients within the plant.