Transformation formulas of theta-series with harmonic polynomials of one-class quadratic forms under Hecke operators are interpreted as a result of interaction of the standard representation of the symplectic Hecke-Shimura ring on theta-series with the natural representation of the orthogonal Hecke-Shimura ring on the same theta-series considered as invariants of quadratic forms. Properties of the interaction rnaps and their relations to the action of Hecke operators are considered. Bibliography: 9 titles.