ABSTRACT
Crop plants are now cultivated under more stressful conditions than in previous decades. Increases in global temperatures, environmental pollutions, drought stress, salinity and heavy metal accumulation are the main stressors, and they would possibly be the leading stress factors for the coming decades. These stress factors have great potential to interact with each other in soil or plants. The combination of abiotic stress factors possibly exerts more drastic consequences on crop plants when compared to those of individual abiotic stress factors. Abiotic stress factors not only interact with each other but also interact with plant pathogens such as bacteria, fungi and viruses. Their combined, sequential or simultaneous, effects might have more consequences on crop plants, and stress arising from abiotic or biotic stresses might be reflected as being much higher under combined stress conditions than originally thought. Abiotic stress factors might stimulate or inhibit each other. However, in most cases, we observe the combined stresses rather than the inhibition of stresses in nature. In an optimistic scenario, the effect of both types of stressors could be added up and, at least, twice as much as the effect of individual stress factors would be observed. In the worst-case scenario, one particular stress factor might stimulate the other stress factor, or the defense responses of defending crop plants may not effectively function due to cross-signaling in the plants. The deleterious effect could be reflected with a much higher impact. These scenarios will gain more interest in the future as the impact of abiotic stress factors increases. In this chapter, abiotic stress factors are summarized individually and their possible interactions are evaluated.
