This review of the literature indicates that certain strains of
PGPR can help plants tolerate drought stress. Some of the
physiological mechanisms that have been proposed include
alterations in root architecture which results in improved water
and nutrient uptake, with positive effects on the overall plant
growth, increase in relative water content, increase in several
organic and inorganic solutes as well as an increase in the synthesis
of osmolytes including proline, increase in antioxidant enzymes
that scavenge for reactive oxygen species, and manipulation of
phytohormones including IAA, ABA, and CK. The research that has
been published so far offers a glimpse into the intricate, complex
and intriguing mechanisms underlying bacterial-mediated
drought tolerance. New studies on these mechanisms will help
improve strategies for the use of PGPR in mediating drought
tolerance.