Effect of nitrogen forms and Ca/K ratio in the culture solution on the contents of nitrate, ascorbic acid and oxalic acid in spinach (Spinacia oleracea L.) and komatsuna (Brassica campestris L.).
1995
Takebe M. | Ishihara T. | Ishii K. | Yoneyama T.
Spinach and komatsuna were cultured in the solutions containing different combinations of Ca and K, and NO3-N and NH4-N, and the changes of the contents of nitrate, ascorbic acid and oxalic acid were investigated. In Experiment I, the meq ratios of Ca and K were 9:1, 5:5 (control) and 1:9, and total meq was 8. In Experiment II, the meq ratios of NO3-N and NH4-N were 10:0 (control), 5:5 and 2:8, and total meq was 4. The content of insoluble oxalic acid was increased along with the increase in the ratio of Ca, while the content of soluble oxalic acid was increased along with the increase in the ratio of K. The meq of Ca was equal to that of insoluble oxalic acid in spinach. So it is considered that the production of insoluble oxalic acid was determined by the amount of Ca in spinach. In spinach, the contents of total oxalic acid was correlated with the content of reduced nitrogen (total nitrogen - nitrate nitrogen), and the content of total oxalic acid was decreased along with the increase in the ratio of NH4-N in the solution. So there was a close relation between the production of oxalic acid and the reduction of nitrate in spinach. In both drops, the content of nitrate was decreased and the content of total ascorbic acid (ASA + DHA) was increased along with the increase in the ratio of HN4-N in the solution. It is suggested that the quality of spinach and komatsuna is better when nitrogen is absorbed as NH4-N rather than as NO3-N.
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