Abstract :
[en] The rhizosphere is the narrow zone where interactions between plant roots, soil and
a myriad of microorganisms affect nutrients biogeochemical cycling (including
phosphorus (P)) and crop productivity. Given the dependency of today’s
agriculture and food production on external P inputs, exploring the ability of roots
and their microbial symbionts to sense the rhizosphere P limitation is emerging as
a potential strategy to optimize P use efficiency. Indeed, dual use of P-solubilizing
rhizobacteria (PSB) and polyphosphate (PolyP) fertilizers, that may exhibit slow P
release property, can be considered as an integrated P management practice in
agricultural soils to enhance P fertilizers use efficiency. In line with that, our recent
published studies (Khourchi et al., 2022b, 2022a) showed that roots and PSB
significantly increased P availability from PolyP under both soils and in vitro
conditions. This hydrolysis process was catalyzed by the exuded P-hydrolyzing
enzymes (phosphatases) and organic acids. For instance, the increased P uptake and
P availability are accompanied with enhanced acid phosphatase activity in the
rhizosphere of inoculated wheat plants under PolyP application. Moreover, the
greenhouse-based experiments demonstrated that inoculation with PolyPhydrolyzing bacteria improved crop performance and P acquisition by modulating
morphophysiological root traits (root length, root hair length and root acid
phosphatases). These beneficial effects of PolyP and PSB can be attributed to
induced rhizosphere processes such as rhizosphere acidification and exudation of
phosphatases directly involved in PolyP hydrolysis. Indeed, PolyP hydrolysis can
be synchronized with the crop P requirement, leading to an optimized and efficient
P acquisition
