Abstract: Endogenous hormones (ABA, IAA, IPA) contents and peroxidase activity during the mannitol and cold pretreatment periods were measured in two varietion ("Igri' and "Har- rington' ) barley (Hordeum vulgate L. ) anther. The results were as follows: Firstly, anther endogenous hormone contents were identical changes in both varieties during mannitol pretreatment period. The endogenous hormone contents of anthers were rapidly increased during the early period of pretreatment, reaching their maximum at the first 12 h or the 1st day. After then. the contents began to reduce until they reached a stable level. The result suggested that combined effect of some endogenous hormones, including ABA, was essential for changing the developmental pathway of pollen. Secondly, similar changes in peroxidase activity during the period of mannitol pretreatment were seen in both barley varieties. The activity of peroxidase was remarkably increased during the early period of pretreatment, being highest at the 3rd day. After that, it was reduced from the 3rd day to the 5th day, but increased again from the 5th day to the 7th day. Finally, there were two peaks of peroxidase activity during the cold pretreatment period, which were at the 2nd day and the 14th day for "Harrington' or the 5th day and the 21st day for "Igri'. The second peak was higher than the first one. A second increase in the peroxidase activity for both genotypes were observed from the 28th day to the 35th day during the cold pretreatment period as this phenomenon was in concert with that of mannitol pretreatment.

Key words: Barley, Microspore dedifferentiation, Pretreatment, Endogenous hormone, Peroxidase