A Survey of Plant Iron Content-A Semi-Systematic Review

Abstract

Iron is an essential mineral nutrient for all living organisms, involved in a plurality of biological processes. Its deficit is the cause of the most common form of anemia in the world: iron deficiency anemia (IDA). This paper reviews iron content in various parts of 1228 plant species and its absorption from herbal products, based on data collected from the literature in a semi-systematic manner. Five hundred genera randomly selected from the Angiosperms group, 215 genera from the Pteridophytes groups and all 95 Gymnosperm genera as listed in the Plant List version 1.1 were used as keywords together with the word "iron" in computerized searches. Iron data about additional genera returned by those searches were extracted and included in the analysis. In total, iron content values for a number of 1228 species, 5 subspecies, and 5 varieties were collected. Descriptive and inferential statistics were used to compare iron contents in various plant parts (whole plant, roots, stems, shoots, leaves, aerial parts, flowers, fruits, seeds, wood, bark, other parts) and exploratory analyses by taxonomic groups and life-forms were carried out. The absorption and potential relevance of herbal iron for iron supplementation are discussed.

Keywords: anemia; food supplements; herbal organs; iron; life-forms; taxonomic groups.

Figure 1

Histogram of iron concentration in the leaf. A zoomed-in histogram (without the largest outliers, covering the interval 0–5000 mg/kg) is provided as an electronic supplementary material, Figure S3).

Figure 2

Iron concentration in root versus leaf. The bars show the differences between iron concentrations in the two organs, computed as percentages from the leaf concentration (bars over zero indicate higher contents in roots, bars under zero indicate higher contents in leaves). A graph with the absolute values is provided as a supplementary electronic material—Figure S13.

Figure 3

(a) Variation of iron concentration along four life stages in Phaseolus vulgaris L. (based on [45]). The error bars are used as declared by the authors, who have not stated the nature of the error measurement, however; (b) Variation of iron concentration along three life stages in Lactuca sativa L. (based on [46]. The error bars are 95% confidence intervals; (c) Variation of iron concentration in the leaves of four fern species depending on life stage. Based on [47].

Figure 3

(a) Variation of iron concentration along four life stages in Phaseolus vulgaris L. (based on [45]). The error bars are used as declared by the authors, who have not stated the nature of the error measurement, however; (b) Variation of iron concentration along three life stages in Lactuca sativa L. (based on [46]. The error bars are 95% confidence intervals; (c) Variation of iron concentration in the leaves of four fern species depending on life stage. Based on [47].

Figure 4

(a) Segmented regression modeling of dialyzable iron in Amaranthus species leaves as a function of total iron in the herbal product; (b) natural cubic spline modeling of the same data. Based on [71].

Figure 4

(a) Segmented regression modeling of dialyzable iron in Amaranthus species leaves as a function of total iron in the herbal product; (b) natural cubic spline modeling of the same data. Based on [71].