Germination, viability, and protein changes during cold stratification of giant ragweed (Ambrosia trifida L) seed

The objective of this study was to investigate the influence of cold stratification on giant ragweed (Ambrosia trifida L.) seed germination and protein changes occurring during stratification. Giant: ragweed seeds were dry afterripened at 4, 8 and 20 degrees C and cool-moist stratified at 4 and 8 degrees C. Germination observations were recorded following 0, 30, 60, 75, 90, 105, and 120 d of afterripening or stratification. Viability was determined using tetrazolium staining. Phenol-extractable proteins were separated in two dimensions using isoelectric focusing (IEF) and sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) electrophoresis. No germination was observed following dry afterripening at 4, 8, and 20 degrees C and stratification at 8 degrees C. The 4 degrees C stratification treatment gave 33 and 58 percent germination at 60 and 90 d, respectively. Seed viability was 82 to 86 percent in both afterripened and stratified treatments. Three silver-stained polypeptides were observed in the axis and cotyledons of dry afterripened and 30 d 4 degrees C stratified seeds. These polypeptides were not found in 60 d 4 degrees C stratified seeds. The absence of these polypeptides was associated with stratification treatments that removed giant ragweed seed dormancy.