More frequent and more intense changes in environmental factors act as a stress on the plants. Faced with these changes, plants have developed mechanisms of tolerance and adaptation, which enable them to survive. These mechanisms operate on the morphological, physiological, biochemical and molecular level, are interconnected, regulated and coordinated in an integrated system response to changes in the environment. Many key regulatory and functional molecules involved in the response to abiotic stress are identified, thus opening the possibility for implementation of new strategies in the stress management. This paper outlines the molecular and biochemical mechanisms of response of woody plants to different types of abiotic stress, with special emphasis on poplars.