ABSTRACT
Plant growth and productivity is adversely affected in the form of various abiotic and biotic stresses. Abiotic stress, in fact, is the principal cause of crop failure worldwide, dipping average yields for most major crops by more than 50% (Bray et al. 2000) and causing losses worth hundreds of million dollars each year. In addition, these stresses threaten the sustainability of agricultural industry. In response to these stress signals that cross talk with each other, nature has developed diverse pathways that act in cooperation for combating and tolerating them. A biological stress is an adverse condition, which inhibits the normal functioning and well-being of plants (Mahajan and Tuteja 2005). Drought is a meteorological term and is commonly defi ned as a period without signifi cant rainfall. Water stress can be defi ned as situation in which plant water potential and turgor are reduced enough to interface with normal functions (Zhu 2002). Desiccation is a much more extensive loss of water which can potentially lead to gross disruption of metabolism and cell structure and eventually to the cessation of enzyme catalyzed reaction (Kage et al. 2004). Severe water stress may result in photosynthetic arrest, metabolic disturbance and fi nally death of plant (Jaleel et al. 2008). Understanding plant responses to drought is of great importance and also a fundamental part for making the crops stress tolerant (Reddy et al. 2004; Zhao et al.2008).
