Book Description

Plants are continually challenged to recognize and respond to environmental stresses so as to avoid adverse effects on growth and development. Acclimation of plants to changes in their environment requires a state of cellular homeostasis achieved by a delicate balance between multiple pathways that reside in different cellular compartments. This coordination may, however, be disrupted during different stresses, especially when the cell or the entire plant is exposed to a rapid decrease in water potential, or when additional environmental parameters are involved (Mittler et al., 2006). When different pathways are uncoupled, electrons that have a high-energy state are transferred to molecular oxygen (O ) to form reactive oxygen species (ROS; Takahashi and Asada, 1988; Mittler, 2 2002). ROS, such as 1O , H O , O ·- and HO·, are toxic molecules capable of causing 2 2 2 2 oxidative damage to proteins, DNA and lipids (Apel and Hirt, 2004). Under optimal growth conditions, ROS are mainly produced at a low level in organelles such as chloroplasts, mitochondria and peroxisomes. However, during stress, their rate of production is dramatically elevated. Injury caused by these oxygen derivatives is known as oxidative stress. This can upset the cellular homeostasis of oxygen free radical production and quenching, and tests the antioxidant capacity of the aerobic cell. Stresses largely influence mechanisms outside the normal range of homeostatic control (Lerner, 1999), that triggers change in its metabolite profile, like formation of compatible solutes, antioxidants, phytoalexins, protein protectants and cryoprotectants (Bohnert and Jehsen, 1996). Therefore, in the current section we have reviewed various stresses, their regulation mechanisms and subsequent effects on plant growth and development.