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.

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Endophytic bacteria are useful for their safe services in plant growth improvement and for ameliorating abiotic and biotic stresses. Salt-tolerant plant-growth-promoting Kocuria rhizophila 14asp (accession number KF 875448) was investigated for its role in pea plants under a saline environment. Salt stress (75 mM and 150 mM NaCl) was subjected to two pea varieties, peas2009 and 9800-10, in a greenhouse under a complete randomized design. Different parameters such as plant growth promotion, relative water content, chlorophyll, antioxidants, and mineral contents were analyzed to elucidate the extent of tolerance persuaded by PGPB (plant-growth-promoting bacteria). Exhibition of adverse effects was noticed in uninoculated varieties. However, inoculation of K. rhizophila improved the morphological parameters, antioxidant enzymes, and minimized the uptake of Na+ in plants under various saline regimes. Pea variety 9800-10 exhibited more tolerance than peas2009 in all traits, such as root and shoot length, fresh and dry biomass, chlorophyll contents, and antioxidant enzymes. Our results showed that halotolerant K. rhizophila inoculation plays a vital role in enhancing plant growth by interacting ingeniously with plants through antioxidant systems, enduring saline conditions.

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Background: Pea is the most important crop and vegetable in the world but it has low yield. There is a need to find the ways for the improvement of crop productivity. Plant growth regulators (PGRs) are extensively used in many crops for enhancement of yield and quality. This study was designed to find the influence of PGRs on growth, yield and quality of pea cultivars grown in Pakistan. Methods: Pot experiments were conducted to evaluate the effect of various plant growth regulators (IAA, NAA and GA3) on pea during 2018-19. Four cultivars of pea i.e. Meteor, Green cross, Sultan and Dollar were used in these experiments. There were 0, 100 and 200 mmol’×L-1 levels for each hormone that were applied as foliar spray after 14 days of germination. Experiment was laid down in completely randomized design (CRD) with three replicates. Results: Morphological, biochemical and yield attributes significantly increased in four cultivars of pea except variety Sultan for few parameters. Cultivar Meteor showed highly positive increasing effects on growth and yield attributes as compared to other treatments. Catalases (CAT) activities were increased and peroxidase dismutase (POD) activities were reduced. It can be concluded that reduction in POD activities helped to increase the defense mechanism of plants and high CAT activities caused better balance in plant metabolism as a result growth, yield and quality of pea were increased. All the variables including shoot length, shoot biomass, number of fruits, total seed yield, carbohydrates and protein had positive correlation with phytohormones. These outcomes might be good indicators to predict the best pea cultivars that can have positive promising response for growth, yield and quality traits under plant growth regulators (PGR).

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