Nitric Oxide Functions as Intermediate in Auxin, Abscisic Acid, and Lipid Signaling Pathways

Nitric oxide (NO) is a chemical messenger that actively operates in the plant kingdom. In recent years, NO has been shown to be involved in many and diverse growth, developmental, and physiological processes in plants. It has been shown that NO takes part in different hormone signaling pathways and also acts in concert with well-characterized second messengers. In this chapter, we discuss findings that contribute to the understanding of the role/s of NO during root organogenesis and stomatal movement, focusing on the interrelations between NO and the phytohormones auxin and abscisic acid. We emphasize the requirement of calcium as an essential intermediate present in the NO-mediated responses. Finally, novel data concerning the cross-talk between NO and phosphatidic acid signaling pathways in response to (a)biotic stresses are presented and discussed.