  A Particle Tracking Velocimetry experiment has been performed in a turbulent
flow at intermediate Reynolds number. We present experimentally obtained
stretching rates for particle pairs in the inertial range. When compensated by
a characteristic time scale for coarse-grained strain we observe constant
stretching. This indicates that the process of material line stretching taking
place in the viscous subrange has its counterpart in the inertial subrange. We
investigate both forwards and backwards dispersion. We find a faster backwards
stretching and relate it to the problem of relative dispersion and its time
asymmetry.
