Tubers of yellow nutsedge (Cyperus esculentus L.) were collected over a 2-yr period to investigate the variation in abscisic acid (ABA) and total phenols throughout the year. The amount of ABA increased gradually from the end of the summer to November when it reached the highest level (6.81 μg/g fresh wt of tubers). This coincided with the onset of dormancy of the tubers in the field. In April, when a maximum of tubers showed sprouting, no free ABA was detected in tuber extracts. These data seem to indicate that free ABA is, in part at least, responsible for the dormant state of tubers. No obvious relation was seen between the state of dormancy of the tubers and their total phenolic content. It is unlikely that the phenolics as a group have one specific role in regulating dormancy of the tubers, but is possible that individual classes, or individual phenols, may possess significant activity.
