Influence of a cyanobacterial crude extract containing microcystin-LR on the physiology and antioxidative defence systems of different spinach variants.

Plants can be contaminated with cyanobacterial toxins during spray irrigation of lake water containing toxic cyanobacteria. Here, long-term effects of cyanobacterial crude extract (containing microcystin-LR) on the growth and physiology of different spinach (Spinacia oleracea) variants under semifield conditions were investigated. Changes in antioxidative enzyme activities, and in glutathione, ascorbate and tocopherol contents were investigated to assess the reaction of the antioxidative defence systems in spinach to toxin exposure. In addition to severe morphological effects, such as growth inhibition and chlorosis, the generation of oxidative stress was observed at the cellular level. In response to the negative effects of oxidative stress, plants stimulated an antioxidative system consisting of an enzyme network with superoxide dismutases, peroxidases, catalases, glutathione S-transferases and glutathione reductases, as well as a set of low-molecular-weight antioxidants, including glutathione, ascorbate and tocopherols. Exposure of spinach to cyanobacterial crude extract affected germination, growth and morphology, as well as antioxidative response parameters. Different variants of the same plant reacted in different ways to certain toxicants.