REGULAR ARTICLE Influence of selenium (Se) on carbohydrate metabolism, nodulation and growth in alfalfa (Medicago sativa L.) Anthony Owusu-Sekyere & Juha Kontturi & Roghieh Hajiboland & Somaieh Rahmat & Naser Aliasgharzad & Helinä Hartikainen & Mervi M. Seppänen Received: 10 January 2013 / Accepted: 13 June 2013 / Published online: 5 July 2013 # Springer Science+Business Media Dordrecht 2013 Abstract Background and Aims Selenium (Se) is an essential micronutrient for humans and animals, but its role in plants remains unclear. Selenium enters the food chain via crops, and thus, plants constitute an essential source of Se in human nutrition. As a N 2 -fixing plant of high nutritive value, alfalfa (Medicago sativa L.) is an important forage legume for sustainable agriculture. This study investigated the effects of Se on carbohydrate metabolism, nodulation and growth in alfalfa. In addition, the impact of Se on fructose 1,6-bisphosphatase (F1,6- BPase), a key enzyme in carbohydrate metabolism, as well as on nitrogenase activity in N-metabolism was examined. Methods Alfalfa was grown either in perlite or nutrient solution at different Se (0, 1, 5, 10 and 15 μmol L −1 Na 2 SeO 4 ) and N (2 and 10 mmol L −1 ) concentrations. Plants in perlite were inoculated with Sinorhizobium meliloti and used for studies on nodulation, growth and nitrogenase activity. Plants grown in nutrient solu- tion were used for studies on carbohydrate metabolism. Results Selenium applications (5 and 15 μmol L −1 ) in- creased soluble sugars (SS) in the leaves, on average, by 44 % in both adequate-N and low-N-plants respectively. At the low-N level, Se (10 and 15 μmol L −1 ) increased SS in the stems and roots, on average, by 29 % and 45 % respectively. In adequate-N-plants, Se increased SS in the stems, on average, by 46 % but had no effect in the roots. Selenium (10 and 15 μmol L −1 ) enhanced starch accu- mulation in the leaves about 55 % in low-N-plants. At the adequate-N level, Se (15 μmol L −1 ) increased starch accumulation about 36 %. However, the starch concen- trations in the roots were inconsistent. Selenium also increased F1,6-BPase activity in the upper leaflets. In addition, in low-N-plants, the low Se (1 μmol L −1 and 5 μmol L −1 ) applications increased nodule number (NN) about 40 % and 62 % respectively, but NN decreased with plant growth. In symbiotic plants, Se did not signif- icantly affect nodule fresh weight (NFW), nitrogenase activity and N concentrations. Selenium also had a slight- ly negative effect on dry matter accumulation in shoots and roots of alfalfa. Conclusions The results indicate that, Se up- regulates carbohydrate metabolism via altered re- dox potential which may have some stimulatory effects on nodulation. These effects were, however, Plant Soil (2013) 373:541–552 DOI 10.1007/s11104-013-1815-9 Responsible Editor: Philip John White. A. Owusu-Sekyere (*) : J. Kontturi : M. M. Seppänen Department of Agricultural Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland e-mail: anthony.owusu-sekyere@helsinki.fi H. Hartikainen Department of Food and Environmental Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland R. Hajiboland : S. Rahmat Department of Plant Science, University of Tabriz, 51666-14779 Tabriz, Iran N. Aliasgharzad Department of Soil Science, University of Tabriz, 51666-14779 Tabriz, Iran