Mechanisms behind bacteria induced plant growth promotion and Zn accumulation in Brassica juncea

Mixed planting with a leguminous plant outperforms bacteria in promoting growth of a metal remediating plant through histidine synthesis

“…4a and 4c). As previously demonstrated (Adediran et al 2015), BZn has a higher R value than for BRZn and VZn, such that our fit with Zn oxalate (~52%) and Zn sulfate (~39%) can potentially be improved with addition of another species for which we do not have a standard spectrum, such as Zn malate which has been observed to accumulate in other phytoremediating plants (Sarret et al 2002). Our tentative interpretation of Zn speciation in BZn plant roots is supported by other studies that showed Zn oxalate accumulation in the root of Zn-resistant ecotypes of Silene cucubalus and Rumex acetosa planted on Zn spiked nutrient medium (Mathys 1977).…”

“…Growth and Zn remediation ability was enhanced by inoculation with PGPB, as shown in our previous study (Adediran et al 2015), but the use of leguminous plants to enhance soil phytoremediation has not previously been compared with PGPB. Hence we compared the use of PGPB to promote the growth and phytoremediation efficiency of B. juncea with the use of the leguminous plant V. sativa.…”

“…trifolii (strain WSM1325) isolated from the rhizosphere of a leguminous plant (School of Biological Sciences, University of Edinburgh, UK). The bacteria strains have been demonstrated to have plant growth promoting abilities under Zn contamination (Adediran et al 2015). A standard soil for pot experiments, Scotts Levington F2+S Seed & Modular growth medium (Green-tech Ltd., UK) (Vicente et al 2012), was used.…”

“…This was deemed sufficient to provide space for each plant to grow whilst maximizing rhizospheric interaction between the two plants to test the hypothesis of V. sativa conferring Zn toxicity tolerance to B. juncea. For the bacteria inoculated treatments, cells of P. brassicacearum and R. leguminosarum were cultured in nutrient broth at 30°C to an exponential growth stage and treated as described in Adediran et al (2015). Surface sterilized seeds of B. juncea plants were incubated under aseptic conditions at 30°C in a suspension of bacteria in sterile water (absorbance of 0.5 at 600 nm) for 3 h. We have previously investigated the toxicity of Zn to the bacteria strains used and reported a sufficient population of live bacteria cells under Zn 400 -600 mg l -1 (Adediran et al 2015).…”

“…This inoculation system has been shown to provide active root colonization until the end of the 6 week plant growth experiment under Zn (Adediran et al 2015). Seeds for the control treatments were soaked in sterile deionized water in the same conditions.…”