Supplemental boron stimulates ammonium assimilation in leaves of tobacco plants (Nicotiana tabacum L.)

The aim of this work was to analyse the response of NH4+ assimilation in leaves of tobacco plants (Nicotiana tabacum L. cv. Tennessee 86), to different B applications (B1, 5 muM H3BO3; B2, 10 muM H3BO3; B3, 20 muM H3BO3). The plants were grown under controlled environmental conditions and received a complete nutrient solution. In this experiment, we analysed the foliar concentrations of B and NH4+, as well as the corresponding enzymatic activities: GS,GOGAT, GDH, PEPC; the end products of this assimilation, amino acids and proteins; and finally the concentration of non-structural sugars. Our results indicated that the different B treatments influenced the utilization of NH4+ by tobacco leaves. The B3 treatment registered the lowest NH4+ concentration, and B1 the highest, due probably to the higher GS, GOGAT and GDH activities registered at B3. Conversely, a decline in the concentration of non-structural sugars was recorded at B3. In addition, the high assimilation rate caused a progressive accumulation of amino acids as well as proteins, and boosted biomass production in the leaves.