The effects of freeze-preservation on some pollen enzymes. 1. Freeze-thaw stresses

Abstract

Summary Isozyme patterns of nonspecific esterase, leucine aminopeptidase, acid and alkaline phosphatases and peroxidase were studied to aid explanation of the nature of freeze-thaw injury to pollen. Fresh samples of Lilium longiflorum L. and Zea mays L. pollen were frozen at rates between 200 and 0.5°C/min and thawed at rates ranging between 218 and 2.5°C/min. Soluble enzymes were extracted from pollen and analyzed by disc electrophoresis on 7.5% polyacrylamide gels. The gels were stained for enzymes using substrate specific stains and the stained gels were scored for isozyme patterns, migration rate and relative activity. The data suggest that isozymic alterations of nonspecific esterase, acid and alkaline phosphatases, peroxidase and to a lesser extent leucine aminopeptidase are associated with freezing and thawing treatments. Generally, a decrease in enzyme stainability could be observed with freezing rates below 180 or 150°C/min. A diffused staining pattern of some enzymes may be a reflection of conformational changes. Increased acid phosphatase activity of frozen-thawed samples may indicate lysosomal damage. The isozymes of leucine aminopeptidase remained fairly stable in most treatments.