Protein Synthesis by Plants I. Nitrate Reduction

Reduction of nitrates to nitrites and ammonia was obtained by tomato plant extract in slightly alkaline solution in the presence of fructose or glucose and some free oxygen in darkness as well as in light. 2. The reduction was most active in solutions having a PH value of approximately 7.6. 3. The expressed juice of nitrogen-high tomato plants (containing both nitrates and sugar in abundance), after adding N/10 NaOH to bring to a PH value 7.6, gave a very rapid reduction of nitrates to nitrites at 50° C. 4. The expressed juice of carbohydrate-high tomato plants (containing much sugar but no nitrates), brought to PH 7.6, gave no reaction for nitrites after 20 hours at 50° C. Upon addition of nitrates there was even more rapid reduction than by the nitrogen high juice. 5. Tomato plant juice boiled and brought to a PH value 7.6 reduced nitrates as rapidly as the unheated juice. 6. The rate and amount of reduction of nitrates to nitrites by tomato plant extract were exactly the same in darkness as in light. 7. Probably the rate of reduction of nitrates to nitrites by carbohydrate-high tomato plants in darkness was the same as in light for the first few days. Then disturbing differences appeared which are not yet understood. 8. In carbohydrate-high tomato plants the reduction of nitrates was localized in the following regions: at the stem tip just behind the growing region; in the leaf cells, especially near the phloem and in the cortical cells of the petioles; in the stem, especially near the nodes, in the phloem parenchyma, and in cells in the cortex near the phloem. 9. All these regions were slightly alkaline in reaction. The pith cells were acid. In the carbohydrate-high plants before nitrate was supplied there was less difference. The pith cells were slightly acid while the phloem parenchyma was about neutral in reaction. 10. Amino acids (newly synthesized) appeared at the nodes and in petioles and blades of young leaves and just behind the stem tips of carbohydrate-high tomato plants three or four days after nitrate had been supplied to the soil. The amino acids were aspartic acid, asparagin, alanine, leucine, cystine, and histidine.