The study of molecular and biochemical responses of plants to abiotic stress is very complex depending not only on the severity and duration of the stress event, but also on the developmental stage and morphological/anatomical parameters of the plants. The full activation of all signal cascades induced by a given stress event promotes acclimation and leads to stress tolerance. Many families of transcription factors have been shown to be involved in stress-induced signalling cascade in plants. The analysis of the signalling pathways pointed to an extensive cross talk between drought and cold responses and many genes commonly are induced or repressed in the two stress conditions. The plant response to a stress event can greatly change relative to the stress conditions or the life stage. The expression profiles of many genes change in response to water stress treatment, depending on developmental phase, tissue and stress protocols. When subjected to stress, the plants adjust their cellular metabolism to a new condition in coordination with the developmental program of the specific tissues and cell types. For this reason, it is not so simple defining a gene as water stress related, and a gene described as water stress responsive in one particular condition may not behave the same way in another condition.