Changes in activity and isozymes of peroxidase during in vitro dedifferentiation and callus proliferation in different explants of soybean

Total activity of peroxidase and its isozymic profiles in the explants of s oybean during the process of dedifferentiation was investigated. The explan ts obtained from aseptically germinated seedling were transferred to callus ing medium containing MS salts supplemented with 9.0 mu M (2.0 mgl(-1)) 2,4 -D and 6.9 mu M (1.5 mgl(-1)) Kinetin. Total activity of peroxidase increas ed in hypocotyl (0.75 to 1.80), cotyledon (0.55 to 1.20) and internode (0.3 1 to 1.00) during dedifferentiation process with a peak of activity observe d prior to callus initiation. In leaf however, there was a sharp decline in enzyme activity (1.42 to 0.30) after excission with a moderate increase (0 .96) prior to callus initiation. Electrophoretic pattern of peroxidases wer e organ specific. The explant of hypocotyl internode and leaf had three ban d each but with different Rf values. The expant of cotyledon showed only on e isozyme. In all the explants marked changes were associated with the proc ess of dedifferentiation. Once the meristematic activity was triggered no f urther qualitative changes took place in the isozymes. Calluses of all the four explant had only two bands and these persisted during successive subcu ltures.