Shoot growth in Ilex paraguariensis plants grown under varying photosynthetically active radiation is affected through gibberellin levels

The aim of this work was to analyse the response ofNH₄⁺ assimilation in leaves of tobacco plants(Nicotiana tabacum L. cv. Tennessee 86), to different Bapplications (B1, 5 M H₃BO₃; B2, 10M H₃BO₃; B3, 20 MH₃BO₃). The plants were grown under controlledenvironmental conditions and received a complete nutrient solution. In thisexperiment, we analysed the foliar concentrations of B andNH₄⁺, as well as the corresponding enzymaticactivities: GS,GOGAT, GDH, PEPC; the end products of this assimilation, aminoacids and proteins; and finally the concentration of non-structural sugars. Ourresults indicated that the different B treatments influenced the utilization ofNH₄⁺ by tobacco leaves. The B3 treatment registeredthe 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 wasrecordedat B3. In addition, the high assimilation rate caused a progressiveaccumulationof amino acids as well as proteins, and boosted biomass production in theleaves.