The changes of contents of selected free amino acids associated with cadmium stress in Noccaea caerulescens and Arabidopsis halleri

Changes of free amino acid (AA) contents (glutamic acid, glutamine, aspartic acid, asparagines, proline, hydroxyproline) in Noccaea caerulescens and Arabidopsis halleri under cadmium soil contamination (Cd1 = 30, Cd2 = 60, Cd3 = 90 mg/kg soil) are reported. Results of the pot experiment confirmed different effect of wCd on wN. caerulescens in contrast to A. halleri and the higher stress adaptation of A. halleri. Total free AA contents in both plant species were not significantly modified by Cd contamination. The glutamic acid and glutamate contents in plant biomass were decreased under Cd2 and Cd3 stress. The declines of contents of both AA can be caused by intensive syntheses of plant defense elicitors, but declines in A. halleri were significantly lower in contrast to N. caerulescens. The content of aspartic acid was increased in N caerulescens under Cd stress, but in A. halleri its changes were not observed. The different pathways of nitrogen utilization of tested plants were confirmed: the major AA forms used for nitrogen transport are glutamate for N caerulescens and asparagine for A. halleri. The increase of proline content was determined only in N. caerulescens growing under Cd stress in the beginning of growing period.