Studies On Iron Compounds In Plant And Thier Relation To Plant Nutrition:

Sami Mohamed Ali Shata

The aim of this investigation was to study experi-++ +++tbe relative proportions of Fe and Fe in5- ~CONCLUSIONmentlyplant and their relation to some natural chelating ironcompounds, sucb as amino acids, in plant supplied withdifferent rates of iron. Moreover, tbe uptake of somenutrient ele.ents, namely N, P, K, Ca, Mg, Fe, Zn,MD, and Cu were determined to learn more about tbe bebaviourof iron in plant.To satisfy tbese objectives, two greenhous experiments,namely sand culture and calcareous soil pots eXperimentswere carried out. Spinacb plant was used as indicatorplant.)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 ppmFe). Similar trends were also obtained for ferrouScontent in plant. In the mean time, Fe+++ content wassignificantlY 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 inspinach plant were significantly increased with eachincrement of iron application up to 50 ppm. yet ironaddition at low rates. up to 15 ppm Fe, enchanced nitrogenconcentration in plant but higher levels did notaffect these elements materially over that resultedfrom the 15 ppm Fe.5. The P/F.++ ratio tended to decrease significantly byincreasing the rate of iron application. but there wasinsignificant differences between P/Fe+++ ratio at allrates of iron application. Such trend means that thisratio tended to remain constant regardless of the rateat iron application and that any increase of ferriciron is intimately correlated with an increase ot phosphorusconcentration and vice-versa. ~uch data suggestthat the capacity of the plant to absorb and hold iroBin a soluble and mobile form becomes less as the phosphorusconcentration in the plant rises.6. Iron additions partiCUlarly at low rates enhanced thepotassium uptake. but differences tended to diminishedas the rate of iron application was increased.7. No clear trend was noticed in the uptake of calciumand asgnesium under these conditions of experiments.8. Concerning manganese. zinc and copper. iron applicationup to 5 ppm Fe increased the manganese and zincconcentration in plant. however. byond this rate,both elements were significantly decreased. Coppersignificantly decreased with increasing the rate ofiron application.9. In sand culture experiment. F’e-~DTA applications affectedthe concentration of individual free amino acidsdifferently. Compared to the control. iron applicationdecreased the concentration of free alanine, leucine.isoleucine. serine. and phenylalanine. However no cleartrends was noticed with respect to glycine. valine, proline.arginine and histidine. On the other hand. therewas an obvious accumulation of free aspartic, glutamic,threonine and cysteine amino acids with iron application.The .ost important free amino acids chelated withferrous iron were as followlCysteine> histidine> aspartic acid~serine>glutamicacid.10. In calcareous soil experiment, there were decreasingin phenylanine, leucine, valine, arginine, alanine,and proline than the control, whereas, no clear trendswere 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 ofiron application.The most dominant and important free amino acidschelated with Fe++ were as followlcy.hiD> histidine> aspartic acid”/ serine» glutamic acid10. Results indicated that the amount of Fe++ chelated withamino acids are Tery small if compared with the concentrationor the content of Fe++ in plant. Under physiologicalpH, it may be concluded that although the freeramino acids can bind or chelate with fe~ous iron, yetthe free amino acids are not the dominant compound chelatedwith iron in cell or through iron translocation,consequently ferrous and ferric iron, or the activefora. of iron, aust be bound or chelated with othersorganic co.pounds, .ost probably organic acids and phytoferritinwhich seem to play an important role inproteoting the active iron from precipitation or changingte inactive form.