Effects of tungsten on uptake, transport and subcellular distribution of molybdenum in oilseed rape at two different molybdenum levels

Abstract

Due to the similarities of molybdenum (Mo) with tungsten (W) in the physical structure and chemical properties, studies involving the two elements have mainly examined their competitive relationships. The objectives of this study were to assess the effects of equimolar W on Mo accumulation, transport and subcellular distribution in oilseed rape at two Mo levels with four treatments: Mo₁ (1μmol/L Mo, Low Mo), Mo₁+W₁ (1μmol/L Mo+1μmol/LW, Low Mo with Low W), Mo₂₀₀ (200μmol/L Mo, High Mo) and Mo₂₀₀+W₂₀₀ (200μmol/L Mo+200μmol/L Mo, High Mo with high W). The fresh weight and root growth were inhibited by equimolar W at both low and high Mo levels. The Mo concentration and accumulation in root was increased by equimolar W at the low Mo level, but that in the root and shoot was decreased at the high Mo level. Additionally, equimolar W increased the Mo concentrations of xylem and phloem sap at low Mo level, but decreased that of xylem and increased that of phloem sap at the high Mo level. Furthermore, equimolar W decreased the expression of BnMOT1 in roots and leaves at the low Mo level, and only decreased its expression in leaves at the high Mo level. The expression of BnMOT2 was also decreased in root for equimolar W compared with the low Mo level, but increased compared with high Mo level. Moreover, equimolar W increased the proportion of Mo in cell wall fraction in root and that of soluble fraction in leaves when compared with the low Mo level. The results suggest that cell wall and soluble fractions might be responsible for the adaptation of oilseed rape to W stress.

Keywords: Molybdenum; Subcellular distribution; Tungsten; Xylem and phloem transport.