When P is scarse in soil solution, plants use different strategies to acquire P, and many like the release of organic acids
or the production of phosphatases are common in both plants and microorganisms. Richardson et al. [35] reviewed the
different plant and microbial strategies that can lead to the improvement phosphorus efficiency in agriculture, and a new
model involving root Ca-uptake controlling P nutrition under P-deficient conditions was recently described [36]. Root hairs
play a very important role in P uptake by plants, and selecting for root hair length and density often improves P acquisition.
Interestingly, inoculation of pea with Penicillium bilaii the P solubilizing fungus of the inoculum JumpStart® increases by
22% the proportion of roots containing root hairs and by 33% the mean root-hair length [37]. Noh Medina [38] isolated a
strain of Bacillus benzoevorans, with PGP activity on tomato, that increased root-hair density and root-hair length by 24
and 70% respectively and these effects were associated to the production of the plant hormone indole-acetic acid and the
cytokinin isopentenyl adenosine.