Change in growth and physiological parameters in soybean seedlings in response to toxic action of copper

Abstract

Soybean (Glycine max l., cv. Alina) seedlings grown for 5 days on medium containing 1.5–50 μm CuSO4 displayed inhibition of their growth and shoot and root system biomass accumulation, and this effect correlated with copper ions’ concentration. The content of chlorophyll in leaves remained unchanged, while the total content of soluble carbohydrates per 1 g fresh leaf and root mass increased. The inhibition of root growth appeared to be marked at a lower concentration of copper ions in the medium as compared to that intensified the entering into root cells of Evans blue, the known indicator of cell viability. Copper ion excess in the medium did not prevent the process of lateral root initiation and their exit on the primary root surface but significantly suppressed their subsequent growth. It was shown that the Cu-stress resulted in changes in filament actin (F-actin) content in the root cells of the seedlings. F-actin amount increased after 20 h growth of the plants on the medium with 10 μM CuSO4, whereas on the medium containing 50 μM CuSO4 F-actin content in root tip cells dropped considerably as compared to the control. The content of F-actin in the root apex became equal to that in the basal part of the root that completed growth. These results allowed us to suggest that fast Cu-stress-induced retardation of soybean seedling growth is likely to be associated with disturbance of organization and functioning of the actin cytoskeleton (AC) leading to inhibition of cell and organs growth and changes in architecture of the root system due to damage of the mechanism of auxin transport and distribution.