Some metabolites and embryo growth of primed tobacco (Nicotiana tabacum L. cv. ‘KFI09’) seeds were observed during priming. The seeds were primed at 15 and 25~circC for 1, 2, 3, 5, 10 and 15 days in a -0.8 MPa polyethylene glycol 6000 (PEG) solution. The time to 50% seed germination (T50 ) was greatly reduced when the seeds were primed at 25~circC when compared with 15~circC . The α -amylase activity and sugars and amino acid contents in the seeds primed at 25~circC greatly increased, while α -amylase activity was similar, and sugar and amino acid contents increased slightly in the seeds primed at 15~circC . When the seeds were primed at 25~circC , growth of the embryo which was enclosed by endosperm was detected, while the endosperm became thinner as the priming duration was extended.d

Tobacco (Nicotiana tabacum L. ‘KF109’) seeds were primed in polyethylene glycol 6000 (PEG 6000) solutions to determine a) what osmotic potential of the solution would be optimal for priming, i.e., critical potential level for preventing germination, and b) what temperature and duration would be the most effective in priming. The germination was completely prevented below -0.8 MPa of PEG 6000, that indicates a optimum water potential for seed priming. Seeds were primed for 0, 1, 2, 3, 5, 10 and 15 days at 15, 20 and 25~circC , respectively, under the-0.8 MPa PEG 6000 solution to find out the most effective temperature and duration for priming. The effectiveness of priming, particularly in germination speed, was observed more distinctly when the primed seeds were germinated at 15~circC than 2 5~circC . The greatest reduction of the time to 50% germination (T/sob 50/) was when the seeds were primed at 25~circC . The reduction rate of the T50 was rapid when primed from 1 day to 8 days and then slowed down in the seeds primed for longer than 8 days. The time from 10 to 90% germination ( T10-90 increased in the primed seeds for longer than 8 days which showed the reversed effect of synchronous germination. However, T50 was reduced continuously in the seeds even primed over 8 days. Thus, the optimum condition for tobacco seeds priming with PEG 6000 solution was -0.8 MPa in osmotic potential of the solution at 25~circC for 8 days.ays