The endogenous messenger, the phytohormone abscisic acid (ABA) plays a major role in plant’s adaption to drought, salinity, cold and other abiotic stresses. In addition to abiotic stress signaling, ABA is involved also in developmental regulation and in responses to diverse biotic stresses. Dehydration stress results in a strong increase in endogenous ABA levels, which can be perceived by RCAR/PYR1/PYL receptors, initiating the ABA signaling pathway to coordinate the genome-wide gene expression, and plants adaptive physiological responses. ABA biosynthesis triggered by environmental cues as well as developmental signals occurs predominantly in vascular parenchyma cells. The measurement of ABA content in different organ/tissues is required to understandings how ABA is produced and delivered within the plants upon various stress conditions and to elucidate its regulatory role in both physiological and transcriptional responses.

Quantitation of ABA can be achieved by two approaches: 1) the use of gas chromatography–tandem mass spectrometry (GC-MS) and 2) the use of immunoassays. Both methods are sensitive to trace amount of ABA down to the low pico-gram (10-12 g/ml FW) range. The GC-MS method needs special facilities, however the antibody based method is relatively simple and can be carried out in laboratory. Here we describe an easy method for ABA extraction from Arabidopsis seedlings, and further determination of ABA levels by competitive ELISA kit.