Effects of Nitrate on Nodulation and Important Element Contents in Inoculated Phaseolus vulgaris L.

In this investigation, the effects of different levels of nitrate on nodulation inoculated root system of Phaseolus vulgaris L. (Shiny red) as well as dry weight of root, stem and leaves and also content and distribution of Na+, K+, Ca++, Mg++ and phosphorus in the organs of treated plants have been studied. The obtained results showed that low amount of nitrate increased dry weight of root, shoot and leaves. In contrast, high amount of nitrate at10 and 15mM decreased above mentioned growth parameters. Increased nitrate levels caused an increase of K+, Na+, Mg++ and Ca++ content of root, stem and leaves. The Na+, Ca++ and Mg++ contents in leaves and K+ contents in root system of plants were considerably higher than their content in other organs. Phosphorus content of different organs of plants also showed an increase when nitrate levels increased. The presence of leghemoglobin in nodules was considered as an index for its nitrogen fixation activity. The size and number of nodule decreased with increasing the nitrate levels. High level of nitrate at15mM completely inhibited nodulation processes