PGPR-Mediated Plant Growth Attributes and Metal Extraction Ability of Sesbania sesban L. in Industrially Contaminated Soils

Abstract

The release of harmful wastes via different industrial activities is the main cause of heavy metal toxicity. The present study was conducted to assess the effects of heavy metal stress on the plant growth traits, antioxidant enzyme activities, chlorophyll content and proline content of Sesbania sesban with/without the inoculation of heavy-metal-tolerant Bacillus gibsonii and B. xiamenensis. Both PGP strains showed prominent ACC-deaminase, indole acetic acid, exopolysaccharides production and tolerance at different heavy metal concentrations (50–1000 mg/L). Further, in a pot experiment, S. sesban seeds were grown in contaminated and noncontaminated soils. After harvesting, plants were used for the further analysis of growth parameters. The experiment comprised of six different treatments. The effects of heavy metal stress and bacterial inoculation on the plant root length; shoot length; fresh and dry weight; photosynthetic pigments; proline content; antioxidant activity; and absorption of metals were observed at the end of the experiment. The results revealed that industrially contaminated soils distinctly reduced the growth of plants. However, both PGPR strains enhanced the root length up to 105% and 80%. The shoot length was increased by 133% and 75%, and the fresh weight was increased by 121% and 129%. The proline content and antioxidant enzymes posed dual effects on the plants growing in industrially contaminated soil, allowing them to cope with the metal stress, which enhanced the plant growth. The proline content was increased up to 190% and 179% by the inoculation of bacterial strains. Antioxidant enzymes, such as SOD, increased to about 216% and 245%, while POD increased up to 48% and 49%, respectively. The results clearly show that the utilized PGPR strains might be strong candidates to assist S. sesban growth under heavy metal stress conditions. We highly suggest these PGPR strains for further implementation in field experiments.

PGPR-Mediated Salt Tolerance in Maize by Modulating Plant Physiology, Antioxidant Defense, Compatible Solutes Accumulation and Bio-Surfactant Producing Genes

“…The ACC deaminase activity was quantified by following the method used by Zainab et al [ 74 ]. Quantity of α-ketobutyrate produced by hydrolysis of ACC was used to estimate ACC deaminase.…”

Bacillus thuringiensis PM25 ameliorates oxidative damage of salinity stress in maize via regulating growth, leaf pigments, antioxidant defense system, and stress responsive gene expression

“…The method of Zainab et al ( 2021 ) was used to quantify the ACC deaminase. To quantify ACCD production by bacterial cultures, they were grown in Tryptic Soy Broth medium (TSB) for 24–48 h. The bacterial cells were harvested and centrifuged pellets were then washed with 0.1 M Tris HCl (pH = 7.5).…”

Bacillus mycoides PM35 Reinforces Photosynthetic Efficiency, Antioxidant Defense, Expression of Stress-Responsive Genes, and Ameliorates the Effects of Salinity Stress in Maize

“…where, As is inoculated sample absorbance and Ar is a reference (un-inoculated broth + CAS reagent + salt conc.). Production of ACC deaminase enzyme by B. mycoides PM35 was determined using the protocol of Zainab et al [31]. To quantify ACC deaminase production by bacterial cultures, they were grown in tryptic soy broth medium (TSB) for 24-48 h. The bacterial cells were harvested and centrifuged then pellets were washed with 0.1 M Tris HCl (pH = 7.5).…”