RELATIONSHIP BETWEEN THE ATP CONTENT MEASURED AT 3 IMBIBITION TIMES AND GERMINATION OF ONION SEEDS DURING STORAGE AT 3-DEGREES-C, 15-DEGREES-C AND 30-DEGREES-C

The possibility of using ATP content as an indicator of seed quality was studied in onion seeds (Allium cepa cv. Wadenswil). The percentage germination and ATP content of imbibed seeds were compared during 145 weeks of storage at three temperatures (3, 15 and 30 degrees C). ATP content, which was undetectable in air-dried seeds (moisture content: 9%, w/w), increased rapidly as a function of imbibition time, as did the fresh weight and respiration rate, reaching a steady-state level after about 17 h. After 36 weeks of storage, the rate of ATP formation was greater for the seeds stored at 3 degrees C than for those kept at 15 and 30 degrees C. Furthermore, the onset of ATP synthesis was delayed. These phenomena, which are likely to be an expression of seed ageing, are useful indicators, allowing the prediction of the loss of seed viability before the decrease in percentage germination which occurred beyond 36 weeks of storage. In addition, the correlation between ATP content and germination capacity of seeds during 145 weeks of storage was excellent (r=0.95 at 15 degrees C and 0.97 at 30 degrees C), provided that a 17 h-imbibition time, specific for onion seeds, was chosen. These results are discussed in terms of the controversy concerning the correlation between the ATP content and germination percentage of seeds.