Several cyanobacteria have been used as effective natural biostimulants under different stresses, but the utilization of Spirulina platensis has not been extensively investigated. The effects of living S. platensis (25 mg/L on dry weight basis) added twice as soil addition on growth, photosynthetic pigmentation, and antioxidant defenses of Triticum aestivum plants grown under normal and two drought stresses (80 and 60% Field capacity) were evaluated. Under drought stress conditions, growth parameters (shoot height, fresh, and dry weights, photosynthetic pigments) and antioxidant defenses were significantly inhibited by recording relatively lower values of the measured characters than the control. The treatment of wheat plants with S. platensis was successful in improving all growth metrics. Under 80 and 60% FWC, the fresh and dry weight of the shoot increased by approximately 25%, while the height of the shoot improved by approximately 33%. The contents of photosynthetic pigment (chl. a, b, and carotenoids) of T. aestivum were significantly induced by 38%, 31%, and 34%, respectively, under 60% FWC. Antioxidant capacity percentages as scavengers of different free radicals (OH¯⋅, H2O2, NO, and metal chelating), and inhibition of lipid peroxidation, in addition to enzymes (CAT and APX), non-enzymatic antioxidants (phenolics, reducing power, total antioxidants) were significantly improved in Spirulina-enriched soil. The activity of antioxidant enzymes (SOD, CAT, POD, and APX) increased significantly in the shoot of wheat seedling by 150%, 83%, 193% and 11%, respectively, under 60% FWC. Components of soluble metabolites (carbohydrates, free amino acids, and soluble proteins) of T. aestivum were significantly enhanced in Spirulina-treated soil. The roots of wheat seedlings treated with S. platensis showed the highest increase in soluble proteins, free amino acids, and soluble carbohydrates (21.67, 4.68, and 41.67 mg g−1 FW, respectively). The application of Spirulina-based biostimulators is aligned with the sustainable agriculture concept by significant improving the content of photosynthetic pigments, confirming the correlation between growth and the measured antioxidants parameters of T. aestivum. The PCA biplot indicated a great contradiction between chlorophyll pigments, soluble metabolites (proteins, amino acids, and carbohydrates), phenolics, reducing power and flavonoids, and all growth indicators and antioxidant abilities. Therefore, the results of this study support the use of the Spirulina platensis treatment, which was mainly effective in improving the growth of wheat plants by reducing the detrimental effects of drought stress in dry conditions.
Sustainable agriculture is a major theme of the Food and Agriculture Organization (FAO) Strategic Framework
2022–2031. Using microbial-based regulators is a sustainable organic approach to accomplish food safety.
Normally, drought is a menace to most crops’ agricultural production, but for leafy green vegetables the matter is
more frustrating due to grade standards. Despite breakthroughs in boosting crop tolerance to drought stress, the
quest for leafy greens remains restricted. The current report is to study the ability of biologically-produced
gibberellin by Fusarium oxysporum in alleviating water stress in leafy vegetable spinach, Spinacia oleracea.
Endophytic Fusarium oxysporum demonstrated high gibberellin production by 200±5.9 mg L 1. Water stress
(100, 75, 50, 25 % field capacity, FC) generated mild to severe abnormal growth and physiological dynamics.
Foliar-applied biological gibberellin (BG) motivated plant yield and quality by boosting various phenotypic and
physiological features in terms of plant height, biomass, and number of leaves accompanied by thicker epicu-
ticular wax, balanced water status, higher photosynthetic pigment, increased osmoprotectants. BG shoulders a
role in upgrading plant liveness via exacerbating antioxidants (anthocyanin, ascorbic acids, total antioxidants,
and flavonoids) joined with activation of secondary metabolizing enzyme phenylalanine ammonia-lyase PAL,
fulfilling consumer demand standards for spinach as well as lowering the content of phenolics and its oxidizing
enzyme polyphenol oxidas (PPO, browning causer). Catalase (CAT), superoxide dismutase (SOD), and peroxidase
(POD) were instigated thus maintaining electrolyte leakage, cellular O2
⋅ , ⋅OH, H2O2, malondialdehyde, and lipid
peroxidation at baseline levels. BG appears to reduce nitrative toxicity via enhancing nitrate reductase (NR)
activity. BG foliar spray increased spinach’s resilience to dehydration and its capacity to produce an adequate
upgraded yield while cultivated with reduced water regimes or even exposed to drought.
