Maize (Zea mays L.) is a salt-sensitive plant that experiences stunted growth and development during early seedling stages under salt stress. Salicylic acid (SA) is a major growth hormone that has been observed to induce resistance in plants against different abiotic stresses. Furthermore, plant growth-promoting rhizobacteria (PGPR) have shown considerable potential in conferring salinity tolerance to crops via facilitating growth promotion, yield improvement, and regulation of various physiological processes. In this regard, combined application of PGPR and SA can have wide applicability in supporting plant growth under salt stress. We investigated the impact of salinity on the growth and yield attributes of maize and explored the combined role of PGPR and SA in mitigating the effect of salt stress. Three different levels of salinity were developed (original, 4 and 8 dS m⁻¹) in pots using NaCl. Maize seeds were inoculated with salt-tolerant Pseudomonas aeruginosa strain, whereas foliar application of SA was given at the three-leaf stage. We observed that salinity stress adversely affected maize growth, yield, and physiological attributes compared to the control. However, both individual and combined applications of PGPR and SA alleviated the negative effects of salinity and improved all the measured plant attributes. The response of PGPR + SA was significant in enhancing the shoot and root dry weights (41 and 56%), relative water contents (32%), chlorophyll a and b contents (25 and 27%), and grain yield (41%) of maize under higher salinity level (i.e., 8 dS m⁻¹) as compared to untreated unstressed control. Moreover, significant alterations in ascorbate peroxidase (53%), catalase (47%), superoxide dismutase (21%), MDA contents (40%), Na⁺ (25%), and K⁺ (30%) concentration of leaves were pragmatic under combined application of PGPR and SA. We concluded that integration of PGPR and SA can efficiently induce salinity tolerance and improve plant growth under stressed conditions.

Worldwide, salinity severely affects agricultural production of crops such as mung bean in arid and semi-arid regions. In saline conditions, various species of Rhizobium can be used to enhance nodulation and induce salinity tolerance in maize. The present study conducted a pot experiment to determine the efficiency of three rhizobial isolates under different salinity conditions, such as 1.41, 4 and 6 dS m⁻¹, on mung bean growth parameters, antioxidant status and yield. Results revealed that salt stress imparted adverse effects on the growth, antioxidants, yield and nodulation of mung bean. Under high salt stress conditions, fresh weights were reduced for roots (78.24%), shoots (64.52%), pods (58.26%) and height (32.33%) as compared to un-inoculated control plants. However, an increase in proline content (46.14%) was observed in high salt stressed plants. Three Rhizobium isolates (Mg1, Mg2, and Mg3), on the other hand, mitigated the negative effects of salt stress after inoculation. However, effects of Mg3 inoculation were prominent at 6 dS m⁻¹ and it enhanced the plant height (45.10%), fresh weight of shoot (58.68%), root (63.64%), pods fresh weight (34.10%), pods number per plant (92.04%), and grain nitrogen concentration (21%) than un-inoculated control. Rhizobium strains Mg1, and Mg2 expressed splendid results at 1.41 and 4 dS m⁻¹ salinity stress. The growth promotion effects might be due to improvement in mineral uptake and ionic balance that minimized the inhibitory effects caused by salinity stress. Thus, inoculating with these strains may boost mung bean growth and yield under salinity stress.

Heavy metal contamination of soil is an alarming environmental dilemma all over the world. With increasing industrialization, timely development of low-cost and eco-friendly remedial techniques for heavy metal-contaminated soil is needed. Phytoremediation is an emerging technique to remove heavy metals from contaminated soil for environmental sustainability. In the present study, ryegrass was used for phytoextraction of lead and cadmium from contaminated soil in a pot experiment. To enhance the bioavailability of heavy metals, cow dung was acidified by amending with elemental sulfur and molasses and also bioaugmented with an SS-16 sulfur-oxidizing strain to boost biological sulfur oxidation and, hence, four chemically different organic products were prepared. The pot experiment was conducted for a period of 60 days under Pb- and Cd-spiked soil for growing ryegrass with the application of a 10% slurry of each acidified organic product. A significant increase in root and shoot fresh mass as well as Pb and Cd accumulation in the root and shoot of the ryegrass was recorded. As compared to the control and the acidified organic product, P4 was the most effective product overall. Bioconcentration and translocation factors of ryegrass for Pb and Cd were also calculated. At the same time, acidified cow dung slurry (10%) also improved the antioxidative defense mechanism of ryegrass. The results suggest that acidified organic products could be effective for phytoextraction of lead and cadmium from contaminated soil, and in the future acidified cow dung slurry can be used to restore heavy metal-polluted soils in an environmentally sustainable way.