Effect of harvest time and soaking treatment on cell cycle activity in sugarbeet seeds

Cell cycle activity in dry and germinating untreated and treated (soaked in water and subsequently in fungicide) seeds of two sugarbeet cultivars, col lected at commercial harvest time (late mature seeds) and about 2 weeks bef ore this (immature seeds), was investigated by flow cytometry, and by immun e-detection of beta-tubulin and the B-subunit of the 11 S globulin. Germina tion capacity and field emergence were tested. With dry seeds of both culti vars, higher G(2)/G(1) ratios were observed in the radicle tips of late mat ure seeds, as compared with those from immature seeds. The late mature seed s contained more partly degraded (soluble) B-subunit of 11 S globulin, typi cal of germinating or primed sugarbeet seeds. Thus events associated with t he onset of germination had occurred in the seed lots collected at commerci al harvest time. The cytoskeleton protein beta-tubulin was not detectable i n dry seeds from either harvest. Western blotting revealed an accumulation of beta-tubulin during germination and this was faster in the late mature h arvested seeds which was correlated with the onset of DNA replication. Soak ing enhanced the rate of cell cycle activation during germination as well a s vigour, germination capacity, and field emergence. There was positive cor relation between the G(2) / G(1) ratio and the traits examined in laborator y and field tests. It is concluded that a combined analysis of proteins and cell-cycle-related events can be used in understanding and predicting suga rbeet seed quality.