Uptake and distribution of Zn and ⁵⁴Mn in wheat grown at sufficient and deficient levels of Zn and Mn II. During grain development

We investigated the uptake and distribution of Zn and Mn in wheat during grain development. Plants were grown in a chelate-buffered nutrient solution with one of the following treatments: control, low Zn or low Mn. Plants were dual-labelled with ⁶⁵Zn and ⁵⁴Mn at 2 and 8 wk post-anthesis for 5 and 24 h, respectively. After labelling, the plants were separated into individual components for analysis. In the plants harvested at 8 wk after anthesis, spikelets were separated into individual structures and analysed for radioactivity.Little or no root-supplied ⁵⁴Mn was distributed to the leaves of both the controls and low-Mn plants during the grain development stages studied here. More ⁵⁴Mn was distributed to the head at 8 wk than at 2 wk post-anthesis. In contrast, root-supplied ⁶⁵Zn was transported to the leaves at 2 and 8 wk post-anthesis.More ⁶⁵Zn was distributed to the leaves of the low-Zn plants than the controls during grain development.More esZn was detected in the head towards grain maturity. Relatively larger amounts of ⁵⁴Mn than ⁶⁵Zn were found in different parts of the florets. Labelled Mn was found in relatively large quantities in the palea, lemma and in the glumes, even though most ⁵⁴Mn was found in the grain. A large percentage of the grain MMn was in the outer pericarp.During grain development leaves may still require Zn but not Mn, which may be due to the requirement of Zn in maintaining membrane structure and function. Distribution of Zn and Mn within the spikelets suggests that Zn may enter the grain via the phloem while Mnmay enter the grain via the xylem.