Macronutrients and trace elements in rye and wheat: Similarities and differences in uptake and relationships between elements

The present study was based on the hypothesis that differential uptake of various elements by similar plant species - wheat and rye - may be explained by the fact that these plants belong to different taxonomic groups. Greenhouse pot experiments were carried out to study similarities and differences in the behaviour of 30 macro- and trace elements in roots, leaves and seeds of wheat and rye. Leaves and seeds of the plant species accumulated many elements differently than roots. Although rye and wheat were grown simultaneously and under the same conditions, they demonstrated different uptake of various nutrients and trace elements. Correlations between concentrations of Ba, Cd, Co, Cs, Mo, Ni, and Sb in roots and leaves of wheat and rye were similar for both plants: they were statistically significant and positive. The correlation coefficients were 0.63 and 0.91 (Ba), 0.68 and 0.60 (Cd), 0.82 and 0.66 (Co), 0.65 and 0.72 (Cs), 0.75 and 0.53 (Mo), 0.84 and 0.49 (Ni), and 0.69 and 0.75 (Sb) in rye and wheat, respectively. We may assume that these elements were translocated within the plants in a similar way. However, relationships between many other elements in the root-leaf system were different in wheat and in rye. Ratios of essential nutrients (K/Na, Ca/Mg, Ca/Sr. Fe/Mn) were also different for these two plants. The most significant differences between wheat and rye were observed for K/Na ratios. For example, the K/Na ratio was 3.2 times higher in roots of rye than in roots of wheat, 2.7 times higher in rye leaves compared to leaves of wheat, and 1.8 times less in rye seeds than in seeds of wheat. Principal component analysis performed on the basis of element concentrations in the plants showed that leaves of the two plant species were well separated into different groups: leaves of rye and leaves of wheat. The same separation was observed for seeds of the plants. On the other hand, despite significant differences between concentrations of many elements in roots of rye and wheat, separation of roots of the plants into different groups was less distinct. The results indicate that data on concentrations of elements in different plant parts, relationships between elements, and nutrient ratios might provide additional information on plant classification and serve as a specific indicator of the plant taxonomy. (C) 2010 Elsevier B.V. All rights reserved.