Plant Stress (Mar 2024)
Scrutinize the integrated role of Azotobacter vinelandii in nitrogen assimilation, photosystem II functionality and aerenchyma formation of Zea mays under moisture stress environment
Abstract
Moisture, salinity, heat, and drought are some of the main ecological extremities that recruit anomalous metabolic process which not only effect the plant growth and development but also lessen the crop production. Present eco-friendly approach was intended to explore the integrated role of soil bacteria (Azotobacter vinelandii) on aerenchyma formation, nitrogen assimilation, chlorophyll biosynthesis and photosystem II functionality in low moisture stress environment were studied. Azotobacter were isolated from the date palm around the harsh environment, later it was purified in lab and were used in plants with two different concentration P1= 2.312 CFU mL−1, P2 = 2.316 CFU mL−1. Two-week old treated (P1 and P2) and untreated (P0) plants were exposed to 20 ± 5 % and 45±5 % soil moisture content (SMC) while 75 ± 5 % moisture served as positive control using water holding capacity technique. In stress environment, Azotobacter with two concentrations (P1= 2.312 CFU mL−1, P2= 2.316 CFU mL−1) improved the plant length and biomass production demonstrates lesser declined (2 to 3.9 %) in seedling growth and (21.5 to 39.8 %) in biomass production as compared 31.5 to 49.8 % in control plants (P0). Relative water content (RWC) was greatly sustained in moisture stress due to bacterial applications showing 0.02 to 8.0 % declined as compared 34.9 % in control plants. Likewise lesser decreased (-16.5 to -39.2 %) in osmotic potential was noted in treated plant as compared to control plant (-37.1 to -60.6 %). The sub- optimal stress from moderate to severe instigated significant upsurge of energy loss in plants. The energy loss indicators like non-photochemical quenching coefficient (qN) and non-photochemical quenching (NPQ) were relatively high (4.1 to 12.9 % and 33.26 to 47.64 %) in Po as compared to P1 and P2 (0.9 to 1.9 % and 1.3 to 14.2 %) plants. Moreover, application of azotobacter (P1 and P2) also upregulated quantum yield of electron transport (jEo,), the efficiencies of light reaction (φPo / (1- φPo), and biochemical reaction (ψo /(1- ψo) in sub-optimal environment. The upregulation in light harvesting efficiency enhance nitrogen assimilation showing lesser declined in nitrite (21.1 to 9.3 %) and nitrate content (50.0 to 24.0%) in P1 and P2 plants compared to control plants (P0). It was noted that P2 treated plants showed lesser declined in protein content (22 %) corresponding with 8.0 % in nitrite reductase (NIR) and 5.1 % in nitrate reductase (NR) activities. The current finding suggested that the application of azotobacter improve growth and biomass production due sustained photosystem II functionality and nitrogen assimilation under moisture environment. Further, Azotobacter facilitates the aerenchyma formation in plants roots under stress condition enabling gaseous exchange in roots. Application of azotobacter in moisture environment seems to be a promising and eco-friendly solution for sustainable agriculture which not only provide an alternative beside chemical fertilizers but also protect plant against low moisture stress consequences.
