Although it is clear that various PGPR strains help plants
mitigate drought stress, the mechanisms involved remain largely
speculative. Understanding the mechanisms behind the observed
PGPR-observed-drought tolerance mechanisms is important and
will contribute to our ability to improve strategies for the use of
these beneficial bacteria in mediating drought tolerance. Some of
the fundamental questions that remain unanswered are: Is the
observed bacterial-mediated drought tolerance due to IAA or there
are other mechanisms that are yet to be discovered? Does the
observed bacterial-mediated droughttolerance change with plants
physiological status?