High seed Mn content does not affect germination of in vitro produced Centaurium pulchellum seeds
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The effect of high Mn2+ content on Centaurium pulchellum seed germination has been investigated. Seeds containing extremely high Mn2+ content were produced by culturing single-node flowering explants for 2 months in the MS-media, supplemented with Mn in concentrations ranging from 1 to 10,000 mu M. Although the seeds displayed the capacity to accumulate high amount of Mn, their germination was undisturbed. EPR spectroscopy was used to measure the ratio of free (aqueous) Mn to bound Mn and it was found that over 97% of total Mn was in the bound form. With elevating the external Mn supply, seed Mn concentration also increased, but the proportion of free Mn2+ fraction decreased from 3% in the control (1 mu M Mn) to 0.35% and 0.15% in high Mn supply (1000 mu M and 10,000 mu M, respectively). These results suggest that an elevation of internal Mn concentration in seeds is associated with increased Mn binding pools, hence Mn remains bound during germination. Consequently, the action of potentially harmful Mn2+ ions, which may generate ROS and affect seed viability, is alleviated. (C) 2008 Elsevier B.V. All rights reserved.