Azotobacter Modulate Nitrogen Assimilation, Sustain Light Harvesting Efficiency and Photosynthetic Performance of Maize Cultivar in a Saline Soil

The current research was aimed to investigate the sustainable use of Azotobacter (Azotobacter vinelandii) in maize plants under saline environments. Plant responses like nitrogen assimilation, photosynthetic pigments, light harvesting efficiencies and photosynthetic performance contributing to physiological tolerance of maize plant in saline soil were studied. Pure culture of A. vinelandii was obtained from Karachi University Culture Collection (KUCC). Later the seeds underwent bacterial priming with two different concentrations i.e., 40%= 2.3 × 10¹² CFU mL^− 1 (colony forming unit) and 80% = 2.3 × 10¹⁶ CFU mL^− 1(colony forming unit). Two-weeks old primed and un-primed plants were exposed to 0, 50, 150, and 250mM NaCl for 15 days. Azotobacter primed maize plants (40% and 80%) expressed substantial improvements in plant growth and photosynthetic efficiency due to sustainable nitrogen assimilation under saline soil. Osmotic adjustment under salt stress were enhanced in 40% primed plants than un-primed stress plants. Microbial primed plants expressed lesser hydrogen per oxide (H₂O₂) and Malondialdehyde (MDA) production, higher Performance index (PI), and improved effective quantum yield of PSII photochemistry (ΦPSII) under saline soil. Energy loss in term of dissipated heat energy per cross-section (DIo/CS) or non-photochemical quenching (NPQ) were relatively lower in primed maize plants as compared to un-primed plants under stressed environment. The efficiency of light reaction (φPo / (1- φPo), and biochemical reaction (ψo / (1- ψo) were improved in a sub-optimal condition. The role of aerenchyma producing azotobacter in maize plants regarding the upregulation of nitrogen assimilation and improved photosynthetic performance was not investigated before. The current study concluded that the azotobacter not only improved the tolerance in maize plants but also sustained plant growth and biomass production due to upregulation of chlorophyll biosynthesis, nitrogen assimilation and light harvesting efficiency of the plant in saline soil. Hence, azotobacter could be considered as bio-stimulant to get sustainable production in salt effected lands.