Abstract: | Relationships between seed vigour and ethylene (C2H4) productionwere studied using C2H4-responsive fatty cocklebur seeds (Xanthiumpennsyhanicum Wallr.) and C2H4-insensitive starchy pea seeds(Pisum sativum L. cv. Alaska), which had been harvested in differentyears and subjected to different storage conditions. In bothspecies, the seeds with the highest vigour evolved the largestamounts of C2H4 during a period of water imbibition. The reductionof C2H4 production in cocklebur seeds occurred concomitantlywith the reduction in the growth potentials of both axial andcotyledonary tissues. Similarly, the activity of ACC-C2H4 conversionincreased with soaking, and was greater in seeds of high vigourcompared with those of low vigour. However, the change in ACCcontent in pea seeds differed from that in cocklebur seeds.That is, pea seeds with high vigour accumulated less ACC duringan imbibition period than those with low vigour. From theseresults it was suggested that the inferior C2H4 production bylow vigour pea seeds is mainly attributable to low ACC-C2H4conversion, whereas that by low vigour cocklebur seeds is dueto the shortage of ACC supply in addition to the reduced ACC-C2H4conversion. However, germination of deteriorated cocklebur seedswas not restored by exposure to ACC or C2H4, suggesting thatthe loss of seed vigour reduces the responsiveness of seedsto C2H4 as well as C2H4 production. Key words: Pea, cocklebur, seed vigour, ethylene production, 1-aminocyclopropane-1-carboxylic acid |