Seed Germination: Explicit Crosstalk Between Hormones and ROS

Life cycle of a plant (spermatophyte) sets off by germination of seeds that virtually transfer successfully genetic information from parents to off-springs across adverse environmental conditions. Considering the pivotal roles played by both hormones and ROS (especially H2O2 and ˙OH radical) during seed germination, it appears most likely that they function in a coordinated manner having one or more signaling cross-talks. Overwhelming evidences embossed the process of germination diligently controlled by GA-ABA balance; ROS probably being proactive in this event by modulating their metabolism. Ethylene can also be accommodated in this network of regulation, again, through ROS intervention. On the other hand, involvement of PM H+-ATPase in germination is also documented over time. Interestingly, both ROS and phytohormones (e.g. IAA, ethylene) have been reported to modulate PM H+-ATPase activity. Based on its activity of energy-driven transport of H+ across the PM, the H+-ATPase activates cell wall loosening enzymes and proteins like expansins in the context of a redox milieu maintained primarily by NADPH oxidase activity. Nitric Oxide (˙NO), another potential candidate to play a role in signaling, has been documented to regulate seed germination through modulation of hormonal metabolism in a ROS-mediated way. In this chapter, the probable signaling cross-talks among ROS and hormones during seed germination have been discussed with a special emphasis on the role PM H+-ATPase and ˙NO.