If environmental stress exceeds the potential of acclimation, detoxification and reparation, then the cells, tissues, organs and entire plants suffer injury. The latter serves as a bioindication, when it indicates the nature and duration of the stress factor. Exemplary reactions of cells, tissues, organs and entire trees to environmental stress are presented here in words and pictures. The knowledge of such reactions can be used for a differential diagnosis to determine whether the injury is by nutrient imbalance, drought stress, frost, hail, insects, fungus and mite infections or ozone and to estimate their influence.