| A fragment of alginate-derived oligosaccharide (ADO) HZ3 was screened out from 9 oligosaccharides of different origins by comparing the parameters of growth promotion and stress resistance. This active oligosaccharide fragment was identified by ESI-MS method, with the polymerization degree between 2 and 5. The most content of the oligosaccharides mixture were trisaccharide and disaccharide.The growth promotion effects were determined from 3 aspects: plant (including the seed), callus and suspension cells. By soaking the seed with different concentration of HZ3 and then germination, the growth promotion of plants was measured by detecting the shoot and root length, dry weight, protease, lipase, amylases and growth hormones in germination period of pea and maize. The results showed that 0.15% HZ3 showed the best growth promotion effect of pea by enhancing the activity of protease and lipase and the growth hormones of IAA and GA. The 0.20% HZ3 could enhance the growth of maize by promoting the activity of amylase, lipase, protease and hormones of IAA and GA. By measuring the callus inducing rate, the HZ3 exhibited hormone effect and could induce tobacco callus formation. In the procedure of subculture of tobacco callus, the 0.03 % HZ3 showed the best growth promotion effect. In suspension cells subculture, the presence of HZ3 could promote the tobacco cells growth by increasing the content of IAA and GA in the suspension cells.The inducing resistance of the plants by HZ3 towards different adversities was investigated by detecting the damage parameters (MDA and electrolyte leakage), activities of defense enzymes, osmotic substances (including proline, soluble sugar) and some other parameters. The inducing low temperature resistance was testified by spraying the HZ3 solution on the surface of tobacco leaves and stored at 4℃. The presence of HZ3 could induce the changes of various parameters. The defense enzymes activities were enhanced in a short time which could reduce the content of MDA and electrolyte leakage of tobacco leaves. The most effective HZ3 concentration was determined as 0.20%. However, the presence of HZ3 can neither promote the activity of defense enzymes nor the damage of the leaves, suggesting that this concentration of HZ3 exhibited the activity of protecting tobacco leaves from chilling damage. The effects of HZ3 on tomato seedlings under drought stress were detected with the parameters of leaves damage, defense enzymes, stress inducing ABA, and the osmotic substance. The results indicated that 0.20% HZ3 showed the best drought resistance inducing effect which could reduce plant damage by increasing the defense enzymes and osmotic substances. With the increasing of ABA, the defense reactions of the tomato plant were increased. The disease resistance was measured in two aspects: anti-TMV and anti-powdery mildew. 0.20% HZ3 exhibited the best anti-TMV and anti-powdery mildew and could reduce the cure time of powdery mildew 2 days ahead of triazolone. The HZ3 also exhibited fresh keeping ability of strawberry.In the final area, the combination mechanism of HZ3 with tobacco cells was investigated by Confocal Laser Seanning Mieroseopy. The results showed that the HZ3 could combine with cell wall and membrance and the combination had the relationship with protein in membrance and no effect with Ca2+-CaM.This study showed that this alginate derived oligosaccharide HZ3 has potential for applications in plant growth promotion and adversities stress resistance in modern agricultures. |
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