Effects of molybdenum on nitrogen metabolism of sugarcane

Abstract

Two nitrogen fixing sugarcane varieties of Brazil RB72/454 and RB86/7575 were employed as the plant materials. They were cultured in nutrient solution containing different levels of Mo i.e. 0mg/L, 0.01mg/L, 0.02mg/L and 0.04mg/L, respectively, in pot trial with sand in greenhouse. The activities of nitrate reductase (NR) and glutamine synthetase (GS), and the contents of NO3 −-N and NH4 +-N were measured at different stages. The results showed that under nitrogenous conditions in the greenhouse, all the Mo treatments increased the activity of NR and decreased the NO3 −-N content compared with the control for both the test varieties. As a result, the treatment with 0.01mg/L Mo increased the activity of GS in RB72/454 after initial elongation stages and that in RB86/7575 at young seedling stage, and it also decreased the NH4 −-N content to improve the nitrogen metabolism. Under non-nitrogenous conditions, after initial elongation stage, the activity of NR was increased and the NO3 −-N content was decreased in both sugarcane varieties treated with different levels of Mo. Furthermore, the activity of GS was higher than the control of RB72/454 and the NH4 +-N content was lower in leaves of RB86/7575 at tillering stage. The effect of different Mo treatment on the process of nitrogen metabolism and ammonia assimilation at different stages of growth was different under nitrogenous or non-nitrogenous condition. The lower concentration of Mo could increase the activities of NR and GS absolutely, decrease the contents of NO3 −-N and NH4 +-N in leaf of the two sugarcane varieties as well as improve the nitrogen metabolism and ammonia assimilation.