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Abstract The aim of this investigation was to study experi- ++ +++ tbe relative proportions of Fe and Fe in 5- ~CONCLUSION mently plant and their relation to some natural chelating iron compounds, sucb as amino acids, in plant supplied with different rates of iron. Moreover, tbe uptake of some nutrient ele.ents, namely N, P, K, Ca, Mg, Fe, Zn, MD, and Cu were determined to learn more about tbe bebaviour of iron in plant. To satisfy tbese objectives, two greenhous experiments, namely sand culture and calcareous soil pots eXperiments were carried out. Spinacb plant was used as indicator plant. )0, 50 and 100 ppm Fe were applied as ferrec-~DTA form. Six rates of iron, namely control, 5, 15, ~be following results and conclusions were recorded’ 1. Total iron uptake increased witb the increasing of Fe- ED!A application up to tbe bigbest rate used (100 ppm Fe). Similar trends were also obtained for ferrouS content in plant. In the mean time, Fe+++ content was significantlY increased only up to 15 ppm Fe application. But at bigher rates, 15, )0. 50, and 100 pp. Fe, there were no significant differences noticed. 4U -blch is • £vlogl_ reflected on iro. 4. Although nitrogen and phosphorus concentrations in spinach plant were significantly increased with each increment of iron application up to 50 ppm. yet iron addition at low rates. up to 15 ppm Fe, enchanced nitrogen concentration in plant but higher levels did not affect these elements materially over that resulted from the 15 ppm Fe. 5. The P/F.++ ratio tended to decrease significantly by increasing the rate of iron application. but there was insignificant differences between P/Fe+++ ratio at all rates of iron application. Such trend means that this ratio tended to remain constant regardless of the rate at iron application and that any increase of ferric iron is intimately correlated with an increase ot phosphorus concentration and vice-versa. ~uch data suggest that the capacity of the plant to absorb and hold iroB in a soluble and mobile form becomes less as the phosphorus concentration in the plant rises. 6. Iron additions partiCUlarly at low rates enhanced the potassium uptake. but differences tended to diminished as the rate of iron application was increased. 7. No clear trend was noticed in the uptake of calcium and asgnesium under these conditions of experiments. 8. Concerning manganese. zinc and copper. iron application up to 5 ppm Fe increased the manganese and zinc concentration in plant. however. byond this rate, both elements were significantly decreased. Copper significantly decreased with increasing the rate of iron application. 9. In sand culture experiment. F’e-~DTA applications affected the concentration of individual free amino acids differently. Compared to the control. iron application decreased the concentration of free alanine, leucine. isoleucine. serine. and phenylalanine. However no clear trends was noticed with respect to glycine. valine, proline. arginine and histidine. On the other hand. there was an obvious accumulation of free aspartic, glutamic, threonine and cysteine amino acids with iron application. The .ost important free amino acids chelated with ferrous iron were as followl Cysteine> histidine> aspartic acid~serine>glutamic acid. 10. In calcareous soil experiment, there were decreasing in phenylanine, leucine, valine, arginine, alanine, and proline than the control, whereas, no clear trends were noticed in tqe concentration of free serine, histidine, glycine, and threonine. On the other hand, there was a tendency for accumulation of free cysteine, aspartic acid, and glutamic with increasing the rate of iron application. The most dominant and important free amino acids chelated with Fe++ were as followl cy.hiD> histidine> aspartic acid”/ serine» glutamic acid 10. Results indicated that the amount of Fe++ chelated with amino acids are Tery small if compared with the concentration or the content of Fe++ in plant. Under physiological pH, it may be concluded that although the free r amino acids can bind or chelate with fe~ous iron, yet the free amino acids are not the dominant compound chelated with iron in cell or through iron translocation, consequently ferrous and ferric iron, or the active fora. of iron, aust be bound or chelated with others organic co.pounds, .ost probably organic acids and phytoferritin which seem to play an important role in proteoting the active iron from precipitation or changing te inactive form. |