The Dynamics of Seed‐Derived Molybdenum Following Seed Priming in Faba Bean ( Vicia faba L.) and Impact on Nitrogen Accumulation

ABSTRACT

Molybdenum (Mo) is required for biological nitrogen fixation because it forms part of the FeMo cofactor of nitrogenase. Seed priming has been shown to increase BNF in other legumes, but its effectiveness has not been tested in faba bean ( Vicia faba L.). This study investigated the dynamics of Mo following seed priming with a Mo solution and whether this improves nodulation or nitrogen accumulation under controlled nitrogen‐free conditions. Faba bean seeds were primed with water or 0.4% sodium molybdate for 4 or 16 h. Preliminary seed analyses confirmed that Mo priming substantially increased seed Mo content, from 7‐ to 17‐μg Mo seed ⁻¹ in water‐primed seeds to approximately 395‐ to 1145‐μg Mo seed ⁻¹ following Mo priming ( F _7,16  = 5620, p  < 0.001), with most Mo initially retained in the testa. Primed seeds were grown in an autoclaved sand–perlite medium supplied with nitrogen‐ and Mo‐free nutrient solution. Across two independent experimental runs ( n  = 8 replicate plants per treatment), nodulation was assessed 30 days after sowing, and biomass, carbon, nitrogen and Mo partitioning were assessed over a 60‐day growth period. Mo seed priming had no significant effect on effective nodule number, nodule dry weight, shoot or root biomass, plant nitrogen accumulation or plant carbon accumulation (all p  > 0.05). However, inferences from mass balance patterns suggest that Mo was progressively mobilised from the testa and redistributed to roots and shoots, particularly following 16‐h Mo priming. These results demonstrate that seed‐derived Mo is retained in the testa and progressively redistributed to vegetative tissues during early growth but that this redistribution did not translate into improved nodulation or nitrogen accumulation under the conditions tested.