Studies on the accumulation of nitrate in horticultural product. I
The accumulation of nitrate in tomato fruits (1)
1968 Volume 37 Issue 2 Pages 178-184
Details
1968 Volume 37 Issue 2 Pages 178-184
Tin has been often found to be dissolved in large amount in canned tomato juice, and it is also known that nitrate in tomato fruits causes tin-dissolving.
This study was carried out to investigate the factors influencing the accumulation of nitrate in tomato fruits and the relation between the initial nitrate content and detinning in canned tomato juice.
The results obtained are as follows:
(1) Nitrate-nitrogen content should be below 5 ppm to minimize the abnormal tin-dissolving in canned tomato juice.
(2) Nitrate-nitrogen content in the fruits examined was in the range of nil to 20ppm, but that in the petiole was 100 to 1, 000ppm, and even that in the calyx, which is adjacent to the fruit, was 10 to 500ppm.
(3) The accumlation of nitrate in the peptiole and calyx was influenced by nitrate level in the fertilizer, but that in the fruit was not significantly affected.
(4) Nitrate content in the fruits increased in process of the maturation and reached to a maximum at the mature green stage and then decreased. Nitrate content in the calyx also increased and reached to a maximum at the early mature green stage and then decreased to a minimum at the breaker stage and increased again.
These indicate that the nitrate reductase activity is lower in the immatured fruit and become higher as ripeness develops.
(5) Modified Hoagland′s solution was used to make the tomato plants grow in sand culture with and without molybdenum, containing 120ppm nitrate-nitrogen which was raised to 360ppm from 7 th to 12th day after the first flower of each cluster opened. The nitrate-nitrogen content in the fruits grown with molybdenum was found to be lower (4.8ppm) than without molybdenum (6.5ppm). On the contrary, nitrate-nitrogen content in the fruits grown in the constant higher level of nitrate (360 ppm nitrate-nitrogen) with molybdenum was only 3.6ppm and that grown without molybdenum was 4.8ppm.
From these results, it may be said that nitrate would accumulate in the tomato fruits grown in molybdenum deficiency and with the additional fertilization of nitrate.
