We consider the dynamics of the Sorkin-Johnston state for a massless scalar field in two dimensions. We conduct a study of the renormalized stress-tensor by a subtraction procedure, and compare the results with those of the conformal vacuum, with an important contribution from correction term. We find a large trace anomaly and compute backreaction effects to two dimensional (Liouville) gravity. We also find a natural interpretation for the mirror behavior of the Sorkin-Johnston state described in previous works.