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FORMANEK, P., ROSSELLE, K., TURCO, A., REJSEK, K., VRANOVA, V.: Mineralization of alanine enantiomers in soil treated with heavy metals and nutrients. Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 1, pp. 49–52 This work deals with the determination of the eff ect of heavy metals and nutrients applied to the soil on alanine enatiomers mineralization with the main focus on evaluating the eff ect on L/D alanine respiration rate ratio. This study was initiated because previous research works revealed a change in L/D amino acid respiration under acidor heavy metal-stress in soil. Generally, D-amino acids artifi cially supplied to soil are less utilized by microorganisms compared with their L-enantiomers. Stress of soil microorganisms cause decreased discrimination of D-amino acids utilization. Also, previous research showed that an application of fertilizers or combinations of fertilizers may aff ect the mineralization rate of L-amino acids diff erently, compared with their D-enantiomers. The results of this study show, that the eff ect of both heavy metals and nutrients on the L/D ratio was not clear, increasing or decreasing this ratio. Further research is necessary to broaden this study. soil alanine, enantiomers, respiration, heavy metals, nutrients D-amino acid enantiomers atifi cially supplied to soil are known to be less utilized by soil micro organisms compared with their L-enantiomers (Martens and Frankenberger, 1993; Hopkins and Ferguson, 1994; Hopkins et al., 1994, 1997; O’Dowd et al., 1997, 1999; O’Dowd and Hopkins, 1998; Landi et al., 2000). This diff erence may be altered under stress conditions. A decrease in L/D glutamine or glutamic acid respiration due to acid-stress accompanied by increasing qCO2 (the metabolic quotient, which represents the ratio between the respiration and the microbial biomass) was reported by Hopkins et al. (1997). The exact mechanism of this decrease is not yet known. Landi et al. (2000) reported a signifi cant decrease in the L/D glutamic acid respiration ratio in forest soil incubated in the presence of highly availab le cadmium content. Various factors which are directly or indirectly involved in soil respiration may be aff ected by presence of heavy metals including substrate availability, enzyme inhibition, death of microorganisms, change in physiology and structure of microbial community (Brookes, 1995; Dahlin et al., 1997; Landi et al., 2000; Renella et al., 2003, 2004; Dai et al., 2004; Khan et al., 2010) when the exact mechanism of heavy metals action on amino acid respiration is not known. The eff ect on amino acids enantiomers mineralization by nutrients applied to the soil has not been studied thoroughly (Hopkins et al., 1997). Generally, fertilizer application may aff ect soil properties including microbial biomass (Zhong et al., 2010). The change of L/D amino acid respiration can be used as a method to indicate stress in diff erent soils. Intensive research is necessary to verify the eff ect of stress factors on L/D amino acid respiration ratio and its usefulness as an indicator to control soils in agriculture etc. An application of fertilizers may affect mineralization rate of L-amino acids diff erently, compared with their D-enantiomers (Hopkins et al., 1997). More research is necessary to understand this process and, perhaps in future, consider further use of these results in e.g. control of soil fertility. 50 P. Formanek, K. Rosselle, A. Turco, K. Rejsek, V. Vranova In this study whe have attempted to determine the eff ect of selected heavy metals on C-mineralization of alanine enantiomers. This work represents preliminary study where the main aim was to determine if application of diff erent heavy metals or nutrients change L/D alanine respiration ratio. Alanine belongs to amino acids which are characterized by low diff erences between mineralization of its enantiomers (Hopkins et al. 1997). MATERIAL AND METHODS A mixed soil sample (= 10 random sub-samples) of up to10 cm depth for experiments was taken from cultivation of Miscanthus x Giganteus in Botanic Gardens and Arboretum of Mendel University in Brno, the Czech Republic (N 49°12’54.240”, E 16°36’41.989”, 235 meters a.s.l). This plant was established there more than >15 years ago on a plot of 291 m2. A er air-drying to reduce moisture to 20 % (w/w) and sieving through 2 mm sieve, the soil contained 2 mg Lor Damino acid enantiomers per g dry soil, heavy metal solution (Co, Cu, Zn, Mn, Ni in form of chlorides or sulphates) or nutrient solution (Ca, K, and NH4 +-N in form of chlorides, and NO3 −-N in form of NaNO3) to obtain 60 % (w/w) moisture. Carbon dioxide which developed in the course of 24 hours was measured at 22 oC by its absorption into 1 ml 1 M NaOH. Heavy metals or nutrients were applied in concentrations 0–500 g . g−1 dry soil, 2 mg amino acid enantiomers per g dry soil was reported to give maximum respiration rate (Hopkins and Fergusson, 1994; O’Dowd et al., 1997, 1999). Each of the analyses were performed fi ve times and soil properties are mentioned in Table I. RESULTS AND DISCUSSION C-mineralization rate a er application of alanine enatiomers without application of heavy metals or nutrients ranged from 9.60 to 26.5 μg C-CO2 . g −1. h−1. The L/D alanine respiration in presence of diff erent heavy metals showed no clear trend (see Fig. 1). I: Selected properties of soil used for experiments Soil properties Value Clay (< 0.002 mm) (%) 28.2 Silt (0.05–0.002 mm) (%) 45.8 Sand (2–0.05 mm) (%) 26.0