  A detailed analysis of nulling was conducted for the pulsars studied in the
Meterwavelength Single-pulse Polarimetric Emission Survey. We characterized
nulling in 36 pulsars including 17 pulsars where the phenomena were reported
for the first time. The most dominant nulls lasted for short durations, less
than five periods. The longer duration nulls extending to hundreds of periods
were also seen in some cases. A careful analysis showed the presence of
periodicities in the transition from the null to the burst states in 11
pulsars. In our earlier work fluctuation spectrum analysis showed multiple
periodicities in 6 of these 11 pulsars. We demonstrate that the longer
periodicity in each case was associated with nulling. The shorter periodicities
usually originate due to subpulse drifting. The nulling periodicities were more
aligned with the periodic amplitude modulation indicating a possible common
origin for both. Most prevalent nulling lasts for a single period and can be
potentially explained using random variations affecting the plasma processes in
the pulsar magnetosphere. On the other hand, the longer duration nulls require
changes in the pair production processes that need an external triggering
mechanism for the change. The presence of periodic nulling puts an added
constrain on the triggering mechanism which also needs to be periodic.
