Interaction between CO2 elevation and nitrogen metabolism in two varieties of Guar (Cyamopsis tetragonoloba) plants

Resumo

The aim of the experimental study is to analyse the consequence of carbon dioxide elevation on activity of nitrate reductase (NR; EC 1.6.6.1), nitrite reductase (NiR; EC 1.7.7.1), glutamate synthetase (GOGAT; EC 1.4.1.13) in leguminous Cyamopsis tetragonoloba leaves. Plants were exposed to different atmospheric carbon dioxide concentrations 300 ppm (ambient) and 490 ppm (an elevated) conditions. A decrease in activity of Nitrate Reductase (NR), Nitrite Reductase (NiR), Glutamate Synthetase (GOGAT) was found in elevated condition when compared to ambient condition. Plant nitrogen on dry weight basis was found to decrease under elevation with no significant change in soil nitrogen. Soil pH was found to change significantly under elevation, thus showing a decline in pH and promoting soil acidiosis. Total plant fresh weight (FW) and total plant dry weight (DW), Leaf area/cm² were found increased in elevated condition. Thus, in Cyamopsis tetragonoloba plant it can be concluded that under carbon dioxide elevation Nitrate reductase, Nitrite reductase and Glutamate synthetase activity is suppressed due to a reduced amount of nitrate translocation and NADH availability for reduction in plant which is correlated with reduction in plant total nitrogen content where as plant growth and biomass is enhanced due to higher carbon fixation.