The present study investigates the germination and growth of Triticum aestivum exposed to two different microcystins (microcystin-LR [where the two variable places in the toxin molecule are leucine (L) and arginine (R) (MC-LR)] and microcystin-RR) and to cell-free cyanobacterial crude extract containing MC-LR. The concentration of the microcystins was set to 0.5 μg L−1 and therefore is in the range of concentrations normally detected in the environment. In three experiments, the inhibition of germination, the inhibition of root and shoot development, photosynthesis, and activity of oxidative stress-response enzymes, such as glutathione-S-transferase, glutathione peroxidase, and glutathione reductase, were measured. All plants were placed in pots containing normal garden soil to investigate the effects of soil in the uptake of toxin by Triticum aestivum. The results showed clear effects on the morphology of roots and shoots, which were inhibited in exposures with cyanotoxins and crude extract. The inhibition of photosynthesis and the elevation of antioxidative-response enzymes indicate the generation of reactive oxygen species due to the exposure to the toxins resulting in oxidative stress for the plants.