Phytotoxic effects of technetium-99 in beans: Influence of cotyledon excision

Abstract The influence of cotyledon excision on the effects of 99 Tc on Tc accumulation, growth and ultrastructure of bean seedlings was studied. In plants with or without cotyledons, 99 Tc accumulated principally in leaves, although leaves of plants without cotyledons showed a significantly higher 99 Tc concentration. Cotyledon excision substantially enhanced the toxic effects of 99 Tc on growth. Light, scanning and transmission electron micrographs from 99 Tc-treated plants without cotyledons display increased autophagic vacuole activity, accumulation of protein bodies in roots, and decreased starch content and severe ultrastructural alterations in chloroplasts. Our results support the hypothesis that 99 Tc toxicity is mainly associated with anabolic processes in developing tissues.