Hadron fragmentation at high energies and quark constituents

The systematics of particle ratios in high-energy pp collisions suggest that the same constituent partons are active in the production of particles at small and large transverse momentum p_T. We relate various features of the pion spectra at small p_T in the fragmentation region and in the central region of pp collisions to corresponding features observed in ep and en collisions assuming that the dissociation of the proton into quark partons is the common underlying process.