The Distribution of Zinc-65 in Agrostis tenuis sibth. and A. stolonifera L. Tissues4

The distribution of ⁶⁵Zn in zinc-tolerant and copper-tolerantplants of Agrostis spp. from toxic mine-tailings in Enflandand Wales was compared with zinc distribution in non-tolerantplants. Isotope was applied in culture solution in which theplants were growing. No differences could be demonstrated betweenthe plants were growing. No differences could be demonstratedbetween the plants by whole-plant radioautography, or by zincanalyses of the tops. Root/shoot ratios calculated from specificactivity values varied with population, the non-tolerant plantshaving the lowest and the zinc-tolerant plants the highest ratio.After solvent (80 per cent ethanol and water) extractions, theroot residue of zinc-tolerant plants contained a higher percentageof ⁶⁵Zn than that of non-tolerant plants. Chemical fractionationof the roots revealed that the main high difference was thatthe amount of ⁶⁵Zn in the pectate extract of the cell wall washigh in zinc-tolerant plants and low in non-tolerant plants.The ⁶⁵Zn distribution in the copper-tolerant plants was similarto that in the non-tolerant plants, indicating that the tolerancemechanisms for the elements are different. Soluble protein andRNA preparations were made but they contained low levels of⁶⁵Zn. An exception was the relatively high value for RNA fromzinc-tolerant A. stolonifera shoots. An anionic complex of ⁶⁵Znin the soluble fraction was investigated. This complex accountedfor most of the radioactivity in A. tennis extracts of shootsbut the concentration of the complex was low in A. stoloniferashoots, and in root extracts of all plants examined.