  A plane symmetric Bianchi-I model is explored in $f(R,T)$ gravity, where $R$
is the Ricci scalar and $T$ is the trace of energy-momentum tensor. The
solutions are obtained with the consideration of a specific Hubble parameter
which yields a constant deceleration parameter. The various evolutionary phases
are identified under the constraints obtained for physically viable
cosmological scenarios. Although a single (primary) matter source is taken, due
to the coupling between matter and $f(R,T)$ gravity, an additional matter
source appears, which mimics a perfect fluid or exotic matter. The solutions
are also extended to the case of a scalar field model. The kinematical behavior
of the model remains independent of $f(R,T)$ gravity. The physical behavior of
the effective matter also remains the same as in general relativity. It is
found that $f(R,T)$ gravity can be a good alternative to the hypothetical
candidates of dark energy to describe the present accelerating expansion of the
universe.
