Effects of Gradient Ethanol Precipitation on the Structure of Pomelo Pectic-oligosaccharides and Their Effectiveness in Rice Seed Priming

Effects of gradient ethanol precipitation on the structure of pomelo pectic-oligosaccharides (POS) and their effectiveness in rice seed priming were investigated. POS powder was dissolved in water and ractionated by gradient ethanol precipitation at the final concentration of 20%, 40%, 60%, and 80% to obtain POS20, POS40, POS60, and POS80, respectively. POS, fractionated POSs solution (10 mg/L), and water were
used to prime rice seeds for 8 h. After priming, the seed germination time was significantly decreased by 10−18%. Unprimed seeds and those primed with water exhibited root lengths of 53.5 mm and 47.3 mm, and shoot lengths of 30.6 mm and 28.8 mm, respectively. Fractionated POS40, which had the highest relative amount of large-sized (DP>5) with 0% degree of methylation, displayed the most robust growth (root length= 58.5 mm and shoot length= 36.8 mm), followed by POS (root length= 57.6 mm and shoot length= 34.6 mm). Our observations imply that both molecular size and functional group play crucial roles in
influencing the bioactivities of POS. Further study is needed to understand these complex relationships.