Impact of Plant Growth Promoting Bacteria on Salicornia ramosissima Ecophysiology and Heavy Metal Phytoremediation Capacity in Estuarine Soils

Abstract

Salicornia ramosissima is a C 3 halophyte that grows naturally in South Western Spain salt marshes, under soil salinity and heavy metal pollution (mostly Cu, Zn, As, and Pb) caused by both natural and anthropogenic pressure. However, very few works have reported the phytoremediation potential of S. ramosissima. In this work, we studied a microbe-assisted phytoremediation strategy under greenhouse conditions. We inoculated plant growth promoting (PGP) and heavy metal resistant bacteria in pots with S. ramosissima and natural non-polluted and polluted sediments collected from Spanish estuaries. Then, we analyzed plant ecophysiological and metal phytoaccumulation response. Our data suggested that inoculation in polluted sediments improved S. ramosissima plant growth in terms of relative growth rate (RGR) (32%) and number of new branches (61%). S. ramosissima photosynthetic fitness was affected by heavy metal presence in soil, but bacteria inoculation improved the photochemical apparatus integrity and functionality, as reflected by increments in net photosynthetic rate (21%), functionality of PSII (F m and F v /F m) and electron transport rate, according to OJIP derived parameters. Beneficial effect of bacteria in polluted sediments was also observed by augmentation of intrinsic water use efficiency (28%) and slightly water content (2%) in inoculated S. ramosissima. Finally, our results demonstrated that S. ramosissima was able to accumulate great concentrations of heavy metals, mostly at root level, up to 200 mg Kg −1 arsenic, 0.50 mg Kg −1 cadmium, 400 mg Kg −1 copper, 25 mg Kg −1 nickel, 300 mg Kg −1 lead, and 300 mg Kg −1 zinc. Bioaugmentation incremented S. ramosissima heavy metal phytoremediation potential due to plant biomass increment, which enabled a greater accumulation capacity. Thus, our results suggest the potential use of heavy metal resistant PGPB to ameliorate the capacity of S. ramosissima as candidate for phytoremediation of salty polluted ecosystems.

Consortia of Plant-Growth-Promoting Rhizobacteria Isolated from Halophytes Improve Response of Eight Crops to Soil Salinization and Climate Change Conditions

“…This highlights the potential of halophytes as a source of PGPR for the formulation of wide-scope biofertilizers. Overall, Biofertilizers 1, 3, and 5 were the most suitable for most crops tested, which indicates that the PGP properties presented by the consortia are more important than the origin of the bacteria, since they come from halophytes that grow in different habitats [25,55,56]. Depending on the interaction of stressors, the PGP properties that promote plant growth will change.…”

Effects of fungal inoculation on the growth of Salicornia (Amaranthaceae) under different salinity conditions

“…Although we did not include in our experiment the endophytic bacteria present in Salicornia roots, fungi and bacteria coexist in the root microbiome and more interestingly, the bacterial community seems to influence the composition of the fungal ones (Furtado et al 2019a). In addition, single bacterial inoculations have been shown to positively affect growth of Salicornia under salt stress (Bashan et al 2000;Zhao et al 2016;Mesa-Marín et al 2020), whereas the effect of single DSE fungal inoculations was unknown until now. It is possible that their co-inoculation contributes to the plant's tolerance to salt stress.…”

“…However, there is still a research gap in the understanding of the ecological function of this association. While endophytic bacteria do positively affect Salicornia growth under high salt stress conditions (Bashan et al 2000;Zhao et al 2016;Mesa-Marín et al 2020), it has previously not been studied whether the mycobiome provides beneficial effects to Salicornia under high salinity.…”

Tailoring Next Generation Plant Growth Promoting Microorganisms as Versatile Tools beyond Soil Desalinization: A Road Map towards Field Application

“…PGPBs can cause "induced systemic tolerance" (IST), involving various physiological and biochemical changes in plants that confer tolerance to biotic and abiotic stresses [121]. The mechanisms include the production of VOCs which are low molecular weight gaseous metabolic compounds that control phytopathogens and induce systemic resistance [39] to various abiotic stressors such as than salinity, drought, high and low temperatures, and heavy metals [122]. Antioxidants work by reducing the damaging effects of ROS, thereby securing the cell, membranes, and biomolecules [123].…”