The Regulatory Networks of Plant Responses to Abscisic Acid

Abscisic acid (ABA), one of the major plant hormones, is involved in various biological processes in plants, especially in the regulation of seed maturation, dormancy and abiotic stress responses, which have strong relationships with crop yields. For these reasons, ABA has been extensively studied for many years. Very recently, several breakthrough studies were published in ABA research. One was the identification of ABA receptors and the establishment of a major ABA signalling pathway. The other was the discovery of the transport activity of ABA among tissues. These findings open new avenues to understanding hormonal response, not only in cells, but also in the whole organism, and for the improvement of crop yields. In this chapter, we will summarise and discuss our knowledge of ABA and provide a perspective led by those processes.