  At present we know nothing about the nature of the dark energy accounting for
about 70% of the energy density of the Universe. One possibility is that the
dark energy is provided by an extremely light field, the quintessence, rolling
down its potential. Even though the underlying particle theory responsible for
the present quintessential behaviour of our Universe is unknown, such a theory
is likely to have contact with supersymmetry, supergravity or (super)string
theory. In these theories, there are plenty of scalar fields (moduli) which are
gravitationally coupled to all the other degrees of freedom and have vacuum
expectation values of the order of the Planck scale. We point out that, in
theories which allow a consistent embedding of quintessence, the generic
gravitational interaction of the moduli fields with the quintessence field
gives rise to a contribution to the energy density from the moduli fields of
the order of the critical energy density of the universe today. Furthermore,
the interaction contribution can generically enhance the negativity of the
equation of state.
