Mo-Inefficient Wheat Response Toward Molybdenum Supply in Terms of Soil Phosphorus Availability

Phosphorus (P) deficiency is a major constraint to crop growth due to strong soil P fixation. The effects of molybdenum (Mo) on leaf anatomy and dynamics of rhizosphere P in Mo-inefficient crops have still not been investigated. A field study was conducted to investigate the effects of long-term fertilization on dynamics of rhizosphere P transformations and leaf anatomy in Mo-inefficient wheat consisting of Mo (+Mo) and without Mo applied (−Mo) treatments. The results revealed that Mo supply increased plant biomass, grain yield, uptake of P and Mo by 34.9%, 14.8%, 98.1% and 654.1% respectively and preserved the leaf cuticle, stomata, chloroplast, and mesophyll tissue cell configuration. Molybdenum application significantly increased the concentration of radially available P fractions [NaHCO₃-Pi (115.5 to 129.8 mg kg⁻¹ and 67.4 to 80.7 mg kg⁻¹) and H₂O-Pi (14.4–21.9 mg kg⁻¹ and 4.63–6.40 mg kg⁻¹)] in rhizosphere and non-rhizosphere soils, respectively. The acid phosphatase (ACP) activity (19.5 μmol day⁻¹ g⁻¹) was highest during March as compared to alkaline (ALP) and phytase (PHY) enzymes in the rhizosphere soil of +Mo treatment. The highest expression of gene lppC (6.11) was observed in rhizosphere soil as compared to non-rhizosphere soil which indicated that higher gene expressions induced the higher P enzymatic activities. Our findings suggest that Mo fertilizer application increases P availability through induced alteration in dynamics of rhizosphere soil P fractions, higher P and Mo assimilation and phosphatases enzymes activities along with preserving the leaf anatomy and ultrastructure of Mo-inefficient wheat.