  Plastic deformation in solids induced by external shear stress is of huge
practical interest. Presence of local crystalline order in polycrystals,
consisting of many grains, distinguishes its deformation pattern from that of
amorphous materials. Despite strong anisotropy, induced by external stress, the
plastic flow and the consequent deformation field show strong dynamical
heterogeneity. The distribution $P(u)$ of particle displacements ($u$) shows
three distinct regimes including a power law scaling regime at moderate
displacements. Using a phase field simulation we show how polycrystals generate
saddle and vortex like flow patterns, which hitherto have been termed as
elementary plastic events in the context of amorphous materials. Interestingly,
such events here find natural explanation in terms of the underlying
dislocation dynamics. We also characterize the spatial distribution of the flow
field using Okubo-Weiss measure.
