Some aspects of runner bean plant response to cadmium at different stages of the primary leaf growth

Abstract

Changes in morphology of primary leaves and ultrastructure of chloroplasts have been studied in runner bean plants (Phaseolus coccineus L., cv. Piękny Jaś) grown on Knop nutrient solution either without Cd or supplied with 2.5-10-5 M Cd (in the form of 3CdSO4•8H2O) in different stages of growth. The metal applied to the nutrient solution during the early stages of growth resulted in a reduction of the leaf area, chlorophyll accumulation increase and small decrease in PSII activity. Conversely to it Cd added at the end of primary leaf growth revealed almost unchanged leaf area but a significant decrease of chlorophyll level and PSII activity. Changes in the leaf morphology (large intercellular spaces in pallisade as well as spongy mesophyll) and ultrastructure of chloroplasts (degradation of intergranal thylakoids and appearance of numerous plastoglobuli) indicating their disorganization were observed only in plants treated with Cd at the end of primary leaf growth. Morphological and ultrastructural disturbances related to the growth stages are discussed in relation to functional changes of the photosynthetic apparatus.

Keywords

• Phaseolus coccineus
• cadmium
• carotenoids
• chlorophyll
• chloroplast ultrastructure
• leaf anatomy
• leaf area