Liquid Cu50Zr50 glass-forming alloy is undercooled by electrostatic levitation up to 311 K below its melting temperature. The dendrite growth velocity is measured as a function of undercooling. A maximum in the velocity-undercooling relation is observed. It is analysed within the dendrite growth theory. The investigations give evidence of a transition from thermally controlled growth at small undercoolings to diffusion-controlled growth at large undercoolings. In the regime where the kinetic interface undercooling dominates, activation energy is determined which is comparable to the activation energy of atomic diffusion. At largest undercoolings deviations from the Arrhenius-like behaviour appear which indicate cooperative atomic diffusion in the temperature range above the glass temperature.