Transfer of calcium-45 and strontium-90 from medium to plant and their translocation in micropropagated potato

Macdonald Campus, McGill University, Department of Natural Resource Sciences, H9X 3V9 Sainte-Anne-de-Bellevue, Quebec, Canada

Abstract

The uptake and translocation of calcium-45 and strontium-90 were studied in potato (Solanum tuberosum) cv. Sierra micropropagated plantlets and cv. Norland microtubers. The absorption of Ca-45 or Sr-90 by plantlets was not significant as the concentrations of either CaCl₂ or SrCl₂ were increased in the treatment solution. However, the percentage uptake of Ca-45 decreased with increasing concentration of these salts. Uptake by roots, stems, petioles, and leaves differed significantly (p < 0.05) regardless of salt concentration. When shoot-tips were immersed in the treatment solutions containing various concentrations of these salts for 161 h while the plantlets were held in a vertically inverted position, considerable amounts of radiolabel were still translocated towards the roots. The Ca-45/Sr-90 ratio assumed a wide range of values as equal amounts of each radioisotope were fed either through root- or tip-immersion. A differential uptake and translocation between the isotopes occurred for the plantlets independent of feeding mechanism. A drop of Ca-45 or Sr-90 (18.5 kBq) onto the periderm of microtubers was restricted in movement to the periderm with virtually no penetration into the inner cortical or medulary tissues. The diffusion coefficient of Sr-90 on the periderm of Norland microtubers was estimated at 6.5 x 10^-8 cm²/s.