Uptake and distribution of65Zn and54Mn in wheat grownat sufficient and deficient levels of Zn and Mn

Abstract

The uptake and distribution of 65 Zn and 54 Mn by wheat (Triticum aestivum cv. Aroona) was investigated. Plants were grown in a chelate-buffered nutrient solution with either sufficient Zn and Mn, low Zn or low Mn. A single representative seminal root from 14-d-old and 42-d-old plants was dual-labelled with 65 Zn and 54 Mn. The 14-d-old plants were harvested every 10 min from 10-140 min of labelling, whilst the 42-d-old plants were harvested after 2 h of labelling. At harvest, each plant was separated into leaves, main stem, unexposed roots, and tillers. In addition, the crown was separated from the stem in the 14-d-old plants. In the control plants labelled at 14 d, 65 Zn was first detected and accumulated in the crown of the roots after 40-60 min. Labelled Zn was then detected in the stem, followed by the leaves. The oldest and youngest leaves received less 65 Zn than the second and third oldest leaves. The plants grown under low Zn conditions accumulated more 65 Zn in their older leaves and transferred 65 Zn to the unexposed roots. Distribution of 54 Mn was similar in the controls to that of 65 Zn, except the older leaves received no 54 Mn. At the second harvest, a similar distribution pattern of 65 Zn and 54 Mn was observed with regard to leaf age. Large amounts of 65 Zn and 54 Mn were detected within the unexposed roots of all treatments. It is suggested that the distribution of root-supplied Zn and Mn may be determined by micronutrient status and its relationship with leaf transpiration rates.