The Distribution of Zinc-65 inAgrostis tenuissibth. andA. stoloniferaL. Tissues4

Abstract

The distribution of ⁶⁵Zn in zinc-tolerant and copper-tolerant plants of Agrostis spp. from toxic mine-tailings in Enfland and Wales was compared with zinc distribution in non-tolerant plants. Isotope was applied in culture solution in which the plants were growing. No differences could be demonstrated between the plants were growing. No differences could be demonstrated between the plants by whole-plant radioautography, or by zinc analyses of the tops. Root/shoot ratios calculated from specific activity values varied with population, the non-tolerant plants having the lowest and the zinc-tolerant plants the highest ratio. After solvent (80 per cent ethanol and water) extractions, the root residue of zinc-tolerant plants contained a higher percentage of ⁶⁵Zn than that of non-tolerant plants. Chemical fractionation of the roots revealed that the main high difference was that the amount of ⁶⁵Zn in the pectate extract of the cell wall was high in zinc-tolerant plants and low in non-tolerant plants. The ⁶⁵Zn distribution in the copper-tolerant plants was similar to that in the non-tolerant plants, indicating that the tolerance mechanisms for the elements are different. Soluble protein and RNA preparations were made but they contained low levels of ⁶⁵Zn. An exception was the relatively high value for RNA from zinc-tolerant A. stolonifera shoots. An anionic complex of ⁶⁵Zn in the soluble fraction was investigated. This complex accounted for most of the radioactivity in A. tennis extracts of shoots but the concentration of the complex was low in A. stolonifera shoots, and in root extracts of all plants examined.