  Planarian is an intriguing model system wherein the effect of electric and
magnetic fields can be studied on various biochemical pathways during cell
morphogenesis. Recent experimental observations have demonstrated the
non-trivial modulation of reactive oxygen species (ROS) levels by a weak
magnetic field during planaria regeneration. However, the underlying
biophysical mechanism behind this remains elusive. In this paper, we study the
radical pair mechanism to explain the effect of weak magnetic fields on ROS
modulation during planaria regeneration to explain the experimental results. We
also investigate the effect of chirality-induced spin selectivity (CISS) on ROS
levels by including it in the framework of the radical pair mechanism. We
conclude that the inclusion of CISS explains the experimental results better
and allows the radical pair model to have more parametric space to satisfy the
experimental constraints. This study explains the crucial process of ROS
modulation by the weak magnetic field with and without CISS, thereby paving the
way to unraveling the vast domain of ROS modulation for desired outcomes.
