Why Study Stress Combination?  
                                          
Traditionally, abiotic stress conditions are studied in plants by applying a single stress condition such as drought, salinity or heat, and analyzing the different molecular aspects of plant acclimation. This type of analysis is, however, in sharp contrast to the conditions that occur in nature, in which crops and other plants are routinely subjected to a combination of different abiotic stresses. In contrast to the “single stress”-type studies practiced in many molecular biology labs around the world, yield loss studies using simultaneous stress exposure in different crops are well-documented in various agronomic and horticulture journals (Fig. 1; Summarized in Mittler 2006). In addition, tolerance to a combination of two different abiotic stresses is a well-known breeding target in corn and other crops. Because the majority of molecular studies, performed under controlled conditions in the laboratory, do not reflect the actual conditions that occur in the field (i.e. stress combination), a considerable gap is likely to exist between the knowledge gained by these studies and the knowledge required to develop plants and crops with enhanced tolerance to field conditions. This gap might explain why many of the transgenic plants with enhance tolerance to a particular biotic or abiotic stress condition, developed in the laboratory, have failed to show enhanced tolerance when tested in the field. A focus on molecular, physiological and metabolic aspects of stress combination is vital to bridge this gap and facilitate the development of crops and plants with enhanced tolerance to field stress conditions.