Studies on the Accumulation of Nitrate in Horticultural Products

Abstract

The study was carried out to investigate the variances of nitrate contents in tomato fruits among five varieties namely Fireball, Amature, Chico, Heinz 1370 and Brehm's Solid Red. The chemical compositions in fruit and nitrate reductase activities in various parts of tomato plant were determined to know the mechanism of the accumulation of nitrate.Nitrate contents in fruits of Fireball and Amature did not decrease during the ripening and were at remarkably high level at the red ripe stage and these vavieties showed high contents throughout the harvest period.Nitrate contents in fruits of Chico, Heinz 1370 and Brehm's Solid Red decreased remarkably from the mature green stage to the red ripe and were little in the red ripe fruits. In fruit of Chico, nitrate content was considerably high only at the beginning of the harvest period, and in Heinz 1370 and Brehm's Solid Red, the contents were always very low during the harvest period.The variances of nitrate contents in the fruits among five varieties were not explained by the chemical compositions, but higher contents of nitrogen, phosphate, and potassium and lower content of calcium were found in the fruit containing higher nitrate.Changes of nitrate reductase activities in various parts of plant during ripening were found to be no significant differences between Fireball and Chico.