{"references": ["B. N. Kaiser, K. L. Gridley, J. N. Brady, T. Phillips and S. D. Tyerman,\n\"The role of molybdenum in agricultural plant production,\" Annals of\nBotany, vol. 96, pp. 745\u2013754. 2005.", "D. I. Arnon and P. R. Stout, \"Molybdenum as an essential element for\nhigher plants,\" Plant Physiol., vol. 14, no. 3, pp. 599\u2013602. 1939.", "R. L. Hamlin, \"Molybdenum,\" in: Handbook of Plant Nutrition, A. V.\nBarker and D. J. Pilbeam, Eds., New York: Taylor and Francis Group,\n2007, pp. 375\u2013394.", "K. S. Smith, L. S. Balistrieri, S. S. Smith and R. C. Severson,\n\"Distribution and mobility of molybdenum in the terrestrial environment,\" in: Molybdenum in agriculture, U. C. Gupta, Ed.\nCambridge: Cambridge University Press. 1997, pp. 23\u201346.", "J. A. C. Fortescue, \"Landscape geochemistry: retrospect and prospect\n1990,\" Appl. Geochem., vol. 7, pp. 1\u201353. 1992.", "K. J. Reddy, L. C. Munn and L. Wang, \"Chemistry and mineralogy of\nmolybdenum in soils,\" in: Molybdenum in agriculture, U. C. Gupta, Ed.\nCambridge: Cambridge University Press. 1997, pp. 4\u201322.", "R. R. Mendel and T. Kruse, \"Cell biology of molybdenum in plants and\nhumans,\" Biochimica et Biophysica Acta, pp. 1568\u20131579. 2012.", "F. Bittner, \"Molybdenum metabolism in plants and crosstalk to iron,\"\nFrontiers in Plant Science, vol. 5, pp. 28. 2014.", "R. C. Severson and H. T. Shacklette, \"Essential elements and soil\namendments for plants: sources and use for agriculture,\" University of\nIllinois, USA: United States Printing Office; 1988, pp. 48.\n[10] K. Pyrzynska, \"Determination of molybdenum in environmental\nsamples,\" Analytica Chimica Acta, vol. 590, pp. 40\u201348. March 2007.\n[11] M. Anke and M. Seifert, \"The biological and toxicological importance\nof molybdenum in the environment and in the nutrition of plants,\nanimals and man. Part 1: Molybdenum in plants,\" Acta Biologica\nHungarica, vol. 58, no. 3, pp. 311\u2013324. 2007.\n[12] H. Marschner, \"Mineral nutrition of higher plants,\" Second Edition.\nLondon: Academic Press. 1995. pp. 369\u2013378.\n[13] Z. Y. Wang, Y. L. Tang and F. S. Zhang, \"Effect of molybdenum on\ngrowth and nitrate reductase activity of winter wheat seedlings as\ninfluenced by temperature and nitrogen treatments,\" Journal of Plant\nNutrition, vol. 22, no. 2, pp. 387\u2013395. 1999.\n[14] M. Yu, C. Hu and Y. Wang, \"Effects of Molybdenum on the\nIntermediates of Chlorophyll Biosynthesis in Winter Wheat Cultivars\nunder Low Temperature,\" Agricultural Sciences in China, vol. 5, no. 9,\npp. 670\u2013577. 2006.\n[15] U. C. Gupta and J. Lipsett, \"Molybdenum in soils, plants and animals,\"\nAdvances in Agronomy, vol. 34, pp. 73-115. 1981.\n[16] S. C. Agarwala, C. P. Sharma, S. Farooq, C. Chatterjee, \"Effect of\nmolybdenum deficiency on the growth and metabolism of corn plants\nraised in sand culture,\" Canadian Journal of Botany, vol. 56, no. 16, pp.\n1905\u20131908. 1978.\n[17] P. A. Ndakidemi, \"Nutritional characterization of the rhizosphere of\nsymbiotic cowpea and maize plants in different cropping system,\"\nDoctoral degree Thesis. Cape Peninsula University of Technology, Cape\nTown, South Africa. pp. 1\u2013150. 2005.\n[18] S. Bambara and P. A. Ndakidemi, \"The potential roles of lime and\nmolybdenum on the growth, nitrogen fixation and assimilation of\nmetabolites in nodulated legume: A special reference to Phaseolus\nvulgaris L.,\" African Journal of Biotechnology, vol. 8, no. 17, pp. 2482\u2013\n2489. 2010.\n[19] H. Marschner, V. R\u00f6mheld and M. Kissel, \"Different strategies in higher\nplants in mobization and uptake of iron,\" Journal of Plant Nutrition, vol.\n9, pp. 695\u2013713. 1986.\n[20] B. Kovacs, Z. Gyori, J. Prokisch, J. Loch and P. Daniel, \"A study of\nplant sample preparation and inductively coupled plasma emission\nspectrometry parameters. Comm. Soil. Sci. Plant. Anal., vol. 27, no. 5\u20138,\n1177\u20131198. 1996.\n[21] B. Kovacs, P. Daniel, Z. Gyori, J. Loch and J. Prokisch, \"Studies on\nparameters of inductively coupled plasma spectrometer,\" Commun. in\nSoil Sci. and Plant Anal., vol. 29, no. 11\u201314, pp. 2035\u20132054. 1998."]}

The aim of the present study was to examine whether increasing molybdenum (Mo) concentration affects the growth and Mo concentration of maize (Zea mays L. cv Norma SC) and sunflower (Helianthus annuus L. cv Arena PR) seedlings within laboratory conditions. In this experiment, calcareous chernozem soil was used and Mo was supplemented into the soil as ammonium molybdate [(NH4)6Mo7O24.4H2O] in four different concentrations as follow: 0 (control), 30, 90 and 270 mg·kg-1. In this study, we found that molybdenum in small amount (30 mg·kg-1) affects positively on growth of maize and sunflower seedlings, however, higher concentration of Mo reduces the dry weights of shoots and roots. In the case of maize the highest Mo treatment (270 mg·kg-1) and in sunflower 90 mg·kg-1 treatment caused significant reduction in plant growth. In addition, we observed that molybdenum contents in the roots and shoots were very low in case of control soil but were significantly elevated with increasing concentration of Mo treatment. Only in case of sunflower the highest 270 mg·kg-1 Mo treatment caused decrease in Mo concentration.