Production of iron enriched vegetables: Effect of feeding time on the rate of increase in foliar iron content and foliar injury
2000
Inoue, K. | Kondo, S. | Adachi, A. | Yokota, H.
The effect of feeding time on the rate of increase in foliar Fe content and foliar injury was investigated. The roots of spinach (Spinacia oleracea L., cv. Leed), leaf lettuce (Lactuca sativa L., cv. Redfire) and bunching onion (Allium fistulosum L., cv. Hakata Kuronegi) were fed ammonium ferric citrate (AFC; 100 mg l–¹) for 3, 6, 9, 12 and 15 h or EDTA-Fe (50 mg l–¹) for 1, 3, 6, 9 and 12 h in a climatron (temperature: 27°C; relative humidity: 45–55%; PPFD: 380 μmol m–² s–¹). The foliar Fe content showed a near linear increase with time in both the AFC- and EDTA-Fe treatments. In the AFC treatment, foliar injuries in spinach occurred after feeding for 12 h and in lettuce and bunching onion after 9 h. In the EDTA-Fe-treatment, foliar injury in all the plants occurred by feeding for 6 h, and the Fe content in these leaves was obviously lower than that in the AFC-treatment for treatments of the same duration. Thus, EDTA-Fe is unsuitable for this treatment from a practical viewpoint. The foliar Fe content (mg per 100 g fresh weight) in spinach (blades), which had no foliar injuries after feeding AFC for 9 h, was 6.00 ± 0.92 (initial value: 0.82 ± 0.06). In lettuce and bunching onion after feeding for 6 h, it was 3.05 ± 0.40 and 2.00 ± 0.32 (initial value: 0.82. ± 0.05 and 0.58. ± 0.04), respectively. From these results, the incremental rate of the foliar Fe content per hour and the treatment time at which the foliar injury appeared can be estimated in advance given certain treatment conditions. Thus leaf vegetables in which the foliar Fe content is known can be produced without foliar injury.
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