Phosphorus acquisition efficiency and transcriptomic changes of maize plants treated with two lignohumates

Lignohumates are gaining popularity in agriculture, but their chemistry and effects on plants vary based on source and processing. The study evaluated two humates (H1 and H2) to boost maize plant performance under different phosphorus (P) availability (25 and 250 M) in hydroponics, while understanding the underlying mechanisms. Humates differed in chemical composition, as revealed by elemental analysis, phenol and phytohormone content, and thermal and spectroscopic analyses. H1 outperformed H2 in triggering plant responses to low phosphorus by enhancing phosphatase and phytase enzymes, P acquisition efficiency, and biomass production. It contained higher levels of endogenous auxins, cytokinins, and abscisic acid likely acting together to stimulate plant growth. H1 also improved the plant antioxidant capacity, thus potentially increasing plant resilience to external stresses. Both humates increased nitrogen (N) content and acted as biostimulants for P and N acquisition. Consistent with the physiological and biochemical data, H1 upregulated genes involved in growth, hormone signalling and defense in all plants, and in P-recycling particularly in low P condition. In conclusion, H1 showed promising potential for effective plant growth and nutrient utilization, especially in low P plants, involving hormonal modulation, antioxidant enhancement, stimulation of P uptake and P recycling mechanisms.