In the fractional quantum Hall effect regime, the diagonal (ρxx) and Hall (ρxy) magnetoresistivity tensor components of the two-dimensional electron system (2DES) in gated GaAs/AlxGa1−x As heterojunctions are measured together with the capacitance between 2DES and the gate. The 1/3-and 2/3-fractional quantum Hall effects are observed at rather low magnetic fields where the corresponding fractional minima in the thermodynamic density of the states have already disappeared, thus, implying the suppression of the quasiparticle energy gaps.