210 samples of onions (Allium cepa Hysam) from 11 conventionally and 10 organically cultivated sites and 190 samples of peas (Pisum sativum Ping Pong) from 10 conventionally and 9 organically cultivated sites in Denmark were collected and analyzed for 63 and 55 major and trace elements, respectively, by high-resolution inductively coupled plasma mass spectrometry. Sampling, sample preparation, and analysis of the samples were performed under carefully controlled contamination-free conditions. Comparative statistical tests of the element concentration mean values for each site show significantly (p < 0.05) different levels of Ca, Mg, B, Bi, Dy, Eu, Gd, Lu, Rb, Sb, Se, Sr, Ti, U, and Y between the organically and conventionally grown onions and significantly (p < 0.05) different levels of P, Gd, and Ti between the organically and conventionally grown peas. Principal component analysis (PCA) applied to the 63 elements measured in the individual onion samples from the 21 sites split up the sites into two groups according to the cultivation method when the scores of the first and third principal components were plotted against each other. Correspondingly, for peas, a PCA applied to the 55 elements measured as mean values for each site split up the 19 sites into two groups according to the cultivation method when the scores of the third and fourth principal component were plotted against each other. The methodology may be used as authenticity control for organic cultivation after further method development.

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The concentration of major and trace elements was determined for tomato (Lycopersicon esculentumcv. Aromata F1) fruits grown in three different substrate systems. The systems were soil and rockwool irrigated with a normal nutrient solution and rockwool irrigated with a nutrient solution with elevated electrical conductivity (EC). At three harvest times, tomato fruits were analyzed for Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Sr, and Zn by ICP-AES and for Cd, Cr, Mo, Ni, Pb, Sn, and V by HR-ICPMS. The concentrations of Ca, Cd, Fe, Mn, Mo, Na, Ni, Sr, and Zn were significantly different (p < 0.05) for tomato fruits grown on the different substrates. Between the harvest times different levels (p < 0.05) were shown for Ca, Cd, Fe, Mn Na, Ni, Sr, Zn Cu, K, Mg, P, Sn, and V. The concentration of Cd was >15 times higher and the concentration of Ca was 50-115% higher in soil-grown fruits than in rockwool-grown fruits. Principal component analysis applied on each harvest split the data into two groups. One group includes soil-grown fruits, and the other group includes rockwool-grown fruits with the two different nutrient solutions.

Here we present a Zn transporter cDNA named MtZIP2 from the model legume Medicago truncatula. MtZIP2 encodes a putative 37 kDa protein with 8-membrane spanning domains and has moderate amino acid identity with the Arabidopsis thaliana Zn transporter AtZIP2p. MtZIP2 complemented a Zn-uptake mutant of yeast implying that the protein encoded by this gene can transport Zn across the yeast's plasma membrane. The product of a MtZIP2-GFP fusion construct introduced into onion cells by particle bombardment likewise localized to the plasma membrane. The MtZIP2 gene was expressed in roots and stems, but not in leaves of M. truncatula and, in contrast to all other plant Zn transporters characterized thus far, MtZIP2 was up-regulated in roots by Zn fertilization. Expression was highest in roots exposed to a toxic level of Zn. MtZIP2 expression was also examined in the roots of M. truncatula when colonized by the obligate plant symbiont, arbuscular mycorrhizal (AM) fungi, since AM fungi are renowned for their ability to supply plants with mineral nutrients, including Zn. Expression was down-regulated in the roots of the mycorrhizal plants and was associated with a reduced level of Zn within the host plant tissues.

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