Uptake, transport and distribution of molybdenum in two oilseed rape (Brassica napus L.) cultivars under different nitrate/ammonium ratios

Abstract

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO₃ ⁻:NH₄ ⁺) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO₃ ⁻:NH₄ ⁺ while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO₃ ⁻:NH₄ ⁺ ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO₃ ⁻:NH₄ ⁺ ratio was more beneficial for L0917. On the contrary, a lower NO₃ ⁻:NH₄ ⁺ ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO₃ ⁻:NH₄ ⁺ ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO₃ ⁻:NH₄ ⁺ ratio conditions.

摘要

目的

采用不同NO₃ ⁻:NH₄ ⁺比的营养液,探索不同氮源 对钼元素在两种甘蓝型油菜(L0917 和ZS11)中 的吸收、转运和分布的影响及品种间的差异。

创新点

在不同氮源条件下,从组织分布、汁液运输、亚 细胞分布以及品种等方面研究了甘蓝型油菜的 钼营养状况。

方法

将甘蓝型油菜L0917 和ZS11 的幼苗在正常营养 液培养20 天后,分别转移至4 种NO₃ ⁻:NH₄ ⁺比 (14:1、9:6、7.5:7.5、1:14)且总氮为15 mmol/L 的营养液中培养15 天后收获。采用原子吸收分 光光度计-石墨炉法测定根、茎和叶不同部位钼含 量,木质部和韧皮部液钼含量,叶肉细胞细胞壁 组分、细胞器组分和可溶性组分钼含量。

结论

在高或低NO₃ ⁻:NH₄ ⁺比条件下,高的钼吸收能力、 木质部转运、韧皮部再迁移以及叶片亚细胞钼储 存在甘蓝型油菜钼积累上扮演重要角色。