Relationship between the ATP content measured at three imbibition times and germination of onion seeds during storage at 3, 15 and 30C

The possibility of using ATP content as an indicator of seedquality was studied in onion seeds {Allium cepa cv. Wdenswil).The percentage germination and ATP content of imbibed seedswere compared during 145 weeks of storage at three temperatures(3, 15 and 30C). ATP content, which was undetectable in airdriedseeds (moisture content: 9%, w/w), increased rapidly as a functionof imbibition time, as did the fresh weight and respirationrate, reaching a steady-state level after about 17 h. After36 weeks of storage, the rate of ATP formation was greater forthe seeds stored at 3C than for those kept at 15 and 30C.Furthermore, the onset of ATP synthesis was delayed. These phenomena,which are likely to be an expression of seed ageing, are usefulindicators, allowing the prediction of the loss of seed viabilitybefore the decrease in percentage germination which occurredbeyond 36 weeks of storage. In addition, the correlation betweenATP content and germination capacity of seeds during 145 weeksof storage was excellent (r=0.95 at 15C and 0.97 at 30C),provided that a 17 h-imbibition time, specific for onion seeds,was chosen. These results are discussed in terms of the controversyconcerning the correlation between the ATP content and germinationpercentage of seeds. Key words: Allium cepa, ageing, bioenergetic metabolism, seed quality, temperature storage