Patterns of Total Peroxidase Activity and Isozyme Complement During Development of Selected Maturity Genotypes of Sorghum
- Ching-I Pao and
- Page W. Morgan
Changes in peroxidase activity were studied in two maturity genotypes of sorghum [Sorghum bicolor (L.) Moench] grown under 10-and 14-h photoperiods. The rationale was that peroxidase activity or isozyme complement may represent a means to characterize developmental changes in the maturity genotypes and, possibly, a system to regulate indoleacetic acid (IAA) levels. The maturity genotypes 100M and 38M are near isogenic except for the differences at three of the maturity gene loci. Tissue extracts were separated into soluble (cytoplasm) and ionically or covalently bound wall fractions, which were assayed for total peroxidase activity detected in the cytoplasm and cell wall fractions but not in organelle fractions. On a fresh weight basis, total peroxidase activity did not show consistent changes with age and there were no differences between genotypes. However, on a specific activity basis, the ionically bound peroxidase exhibited the highest activity, which consistently peaked near the time of floral initiation of 38M under both photoperiods and 100M under 10-h photoperiods. A similar activity profile was not observed for 100M, which remained vegetative under 14-h photoperiods. The peroxidase isozyme complement was studied by gel electrophoresis with 100M grown under 10-h photoperiods as a model system. There were modest quantitative changes; however, qualitative changes were more striking because they occurred near the time of floral initiation on Day 30. In both soluble and covalently bound fractions, the predominant qualitative changes were observed for the cationic isozymes on Days 25 and 30. The obvious changes in specific activity and isozyme pattern imply that peroxidases may play an important role in the control of transition processes from vegetative to reproductive stages.
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