  In this work we study the phenomenological consequences of the environment
dependence of neutrino mass on solar and reactor neutrino phenomenology. Such
dependence can be induced, for example, by Yukawa interactions with a light
scalar particle which couples to neutrinos and matter and it is expected, among
others, in mass varying neutrino scenarios. Under the assumption of one mass
scale dominance, we perform a global analysis of solar and KamLAND neutrino
data which depends on 4 parameters: the two standard oscillation parameters,
Delta m^2 and tan^2(theta), and two new coefficients, which parameterize the
environment dependence of the neutrino mass. We find that, generically, the
inclusion of the environment dependent terms does not lead to a very
statistically significant improvement on the description of the data in the
most favoured MSW LMA (or LMA-I) region. It does, however, substantially
improve the fit in the high-Delta m^2 LMA (or LMA-II) region which can be
allowed at 98.9% CL. Conversely the analysis allow us to place stringent
constraints on the size of the environment dependence terms, which can be
translated on a bound on the product of the effective neutrino-scalar
(lambda^\nu) and matter-scalar (lambda^N) Yukawa couplings, as a function of
the scalar field mass (m_S) in these models.
