THE ROLE OF NITROGEN METABOLISM IN RED CLOVER ADAPTATION TO THE CONDITIONS OF OIL POLLUTED SOIL

Abstract

Previously obtained data concerning nitrogen metabolism features in red clover plants on the primary stages of growth in the oil polluted (5 %) sod-podzolic loamy soil were analyzed. It was revealed that on all investigated stages of plant growth (stage of cotyledon leaves, stage of first true leaf and stage of first trifoliate leaf) in both red clover roots and leaves there were more non-protein nitrogen forms than protein ones. That indicates an adaptive role of low molecular nitrogen-containing compounds under the conditions of oil polluted soil. Changes of different low molecular Nitrogen compounds content and the activity of main enzymes of ammonium assimilation were detected in red clover plants on primary stages of growth in the oil polluted soil. The peculiarities of nitrogen metabolism in red clover plants under the condition of oil polluted soil on the stage of cotyledon leaves are as following: 1) redistribution of nitrates and ammonium content in the red clover organs that testifies to the fact that nitrates restoration normally takes place in leaves, while under the conditions of oil polluted soil – in plant roots; 2) changes in activity of enzymes of glutamate synthase pathway, namely an increase of glutamine synthetase and inhibition of glutamate synthase activities aimed at accumulation of glutamine in roots of the plant and of glutamate – in leaves; 3) amides accumulation, especially, in roots; 4) an increase in proline amount: 7 times in leaves and 3 times – in plant roots; 5) an increase in total amount of free amino acids, most by in leaves. On the stages of first true and first trifoliate leaf, nitrogen metabolism in red clover plants under the conditions of oil polluted soil had different role: 1) inhibited enzymes of glutamate synthase pathway, especially – the glutamate synthase activity in the leaves on the stage of first trifoliate leaf; 2) gradually proline accumulation has been less expressed: its content in leaves was 6 times higher at the stage of first true leaf and just 3 times higher at the stage of first trifoliate leaf; 3) an increase in total amount of free amino acids was not that significant; 4) glutamate dehydrogenase had been increasing by 20 % in the leaves and 60 % in plant roots; 5) amides and arginine were accumulated in both leaves and roots; 6) stress proteins were synthesized, in particular, of the 120 kD protein in plant leaves.
In general, the Nitrogen metabolism in red clover plants at the oil polluted soil on the stage of cotyledon leaves was aimed at quick inclusion of mineral Nitrogen in the transport forms and creation of protective compounds on the stage of the cotyledon leaves, while on the stage of first trifoliate leaf – it aimed at nitrogen re-utilization in the compounds with high C/N ratio.