The valence-quark distributions in strange and charmed particles are determined by introducing different Regge trajectories for different quark flavours in order to take into account the strong SU(3) and SU(4) symmetry breaking. The valence-quark distributions in π, K and D mesons are shown to be quite different. The K-meson valence-quark distributions and the quark fusion mechanism of particle production have been used to calculate the inclusive spectra of vector mesons in K+p interactions at 32 GeV/c which are found to be in a good agreement with experimental data.