Supplemental boron stimulates ammonium assimilation in leaves of tobacco plants (<Emphasis Type="Italic">Nicotiana tabacum</Emphasis> 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 M H3BO3; B2, 10 M H3BO3; B3, 20 M 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. Abbreviations: ATP – adenosinetriphosphate, DW – dry weight, EDDHA – ethylenediamine-di(o-hydroxyphenylacetic acid), FW – fresh weight, GS – glutamine synthetase, GOGAT – glutamate synthase, GDH – glutamate dehydrogenase, PEPC – phosphoenolpyruvate carboxylase