Comparison of the effects of three priming agents in enhancing the chilling tolerance of tobacco seeds during germination

Early spring low temperature hazards are a common problem in southern China's tobacco production areas, leading to slow germination of tobacco seeds. In the present study, spermine (Spm), salicylic acid (SA) and polyethylene glycol (PEG) were used to prime seeds of different tobacco cultivars. After priming, their germina-tion indices were evaluated in an optimal temperature (25 degrees C) germination test and a low temperature (12 degrees C) germination test. In the optimal temperature germination experiment, priming with any of Spm, SA and PEG could improve the germination index (GI) and reduce the mean germination time (MGT) of 'Xiangyang No. 7' seeds. Moreover, priming with Spm or PEG enhanced the vigour indices (VI) at most priming concentrations and durations, while SA priming with 0.5 mmol L-1 for 24 hours improved the germination potential (GE) and SA priming with 0.5 and 0.6 mmol L-1 for 48 hours improved germination potential (GP). For the low temperature germination experiment, Spm or PEG priming treatment based on the optimal temperature germination experiment markedly improved GI and VI, which was confirmed by the enhancement of antioxidative enzyme activities, while the selected SA priming treatments significantly enhanced GI except for at 0.6 mmol L-1 for 12 hours. Our results indicated that Spm, SA and PEG could be used for enhancing chilling tolerance of tobacco seeds and improving seed germination.