DINITROGEN FIXATION (ACETYLENE-REDUCTION) AND NITROGEN ACCUMULATION IN PEAS CULTIVATED UNDER THE STANDARD GROWTH-CONDITIONS

In Pisum sativum cultivated under standard growth conditions the exten t of N2 fixation with time estimated by the acetylene reduction assay (PN2F) and rates of the actual nitrogen accumulation of plant biomass (ANA) were calculated from six independent growth experiments. In the plants inoculated with indigenous soil Rhizobium populations and culti vated on 0.63 mmol/L nitrate level the percentage PN2F:ANA ratios rang ed from 25.7 to 61.5 %. In peas inoculated with the inoculant strain t he PN2F:ANA ratios were markedly higher, ranging from 59.8 to 65.1 %. The plants cultivated on N-free nutrient solutions showed both PN2F:AN A and C2H4:N2 ratios to be somewhat higher compared with the 0.63 mmol /L nitrate cultivated plants.