Evaluating surface drying and re-drying for wheat seed priming with polyamines: Effects on emergence, early seedling growth and starch metabolism

This study was conducted to investigate the benefits associated with re-drying after seed priming with polyamines. Wheat (cv. AS-2002) seeds were soaked in 10 and 20 mg L^-1 aerated solutions of spermidine (Spd), putrescine (Put) and spermine (Spm), and distilled water (CK2) for 12 h at 28 ± 2°C. Untreated seeds (CK1) and priming in distilled water (CK2) were taken as control treatments. Seeds were primed in two sets: In one set, after each treatment, seeds were given three surface washings with distilled water and dried closer to original moisture; in the other, seeds were only surface dried and used immediately. Use of surface-dried seeds after priming was more effective since it reduced emergence time and synchronized the emergence. Moreover, final emergence, shoot and root length, seedling fresh and dry weight were also improved. Improved starch metabolism was considered possible reason of seed invigoration. All the seed treatments resulted in a lower electrical conductivity of seed leachates compared with control; however, there was more decrease in seeds re-dried after priming than the seeds surface dried after priming. Although the effect of all the polyamines was stimulatory, Spd was the more effective for most of the attributes studied. Nonetheless, Put was more effective for seedling fresh and dry weights. All the polyamines were more effective at lower concentrations except Spm, which improved the coefficient of uniformity of emergence at high concentration. To conclude, if immediate sowing is possible, use of surface-dried seeds after priming may be more effective; seed priming with 10 mg L^-1 Spd was the most effective technique when surface dried.