低氮胁迫下壳聚糖对菜用大豆根毛生长发育及结瘤固氮的影响

Effect of Chitosan on Root Hair Growth and Nodulation and Nitrogen Fixation of Vegetable Soybean under Low Nitrogen Stress

以菜用大豆品“日本青”-快生型根瘤菌HH103的共生体系为研究对象,采用蛭石栽培,研究外源壳聚糖对低氮胁迫下菜用大豆的根毛生长和根系抗氧化系统的影响。试验分别在NH_(4)-N和NO_(3)-N下各设4个处理,CK:叶面喷蒸馏水,根部浇灌含有适宜氮素浓度的营养液;T1:叶面喷壳聚糖水溶液,根部浇灌含有适宜氮素浓度的营养液;T2:叶面喷蒸馏水,根部浇灌溶有1/2适宜氮素浓度的营养液;T3:叶面喷壳聚糖水溶液,根部浇灌溶有1/2适宜氮素浓度的营养液。适宜氮素浓度为50 mg·L^(-1),壳聚糖处理浓度为200 mg·L^(-1)(均为前期试验筛选)。结果显示:外源壳聚糖显著提高了NH_(4)-N和NO_(3)-N低氮胁迫下菜用大豆的根瘤数、根瘤鲜重、植株含氮量及植株干重,较T2增幅分别为28%、35%、37%、42%和33%、63%、18%、24%;显著提高了低氮胁迫期间2种氮素形态下菜用大豆的根毛总数、根毛密度、根毛长度以及变形根毛数,使根毛起始距离显著缩短;使根系MDA含量显著降低。上述结果说明,低氮胁迫下,外源壳聚糖可通过促进根毛的形成和生长,进而促进根瘤菌侵染,这可能是其提高低氮胁迫下菜用大豆结瘤能力的重要原因之一,而壳聚糖促进低氮胁迫下菜用大豆根毛的生长可能是由于其缓解了根系膜脂过氧化的结果。

The effects of exogenous chitosan on root hair growth and root antioxidant system of vegetable soybean under low nitrogen stress were studied by using vermiculite cultivation and the symbiotic system of vegetable soy⁃bean‘Nippon green’-rapid-growing rhizobium HH103 as the research object.In this study,four treatments were set up under NH_(4)-N and NO_(3)-N,respectively,CK:spraying distilled water on the leaves,irrigating nutrient solu⁃tion with appropriate nitrogen concentration in the roots;T1:spraying chitosan aqueous solution on the leaves and irrigating the roots with nutrient solution containing appropriate nitrogen concentration;T2:spraying distilled water on the leaves and irrigating the roots with 1/2 suitable nitrogen concentration of nutrient solution;T3:spray⁃ing chitosan aqueous solution on the leaves,and irrigating the roots with 1/2 suitable nitrogen concentration of nu⁃trient solution.The suitable nitrogen concentration was 50 mg·L^(-1),and the concentration of chitosan treatment was 200 mg·L^(-1)(both were screened in previous experiments).The results showed that exogenous chitosan signif⁃icantly increased the nodule number,nodule fresh weight,plant nitrogen content and plant dry weight of vegeta⁃ble soybean under NH_(4)-N and NO_(3)-N low nitrogen stress,which were 28%,35%,37%,42%and 33%,63%,18%,24%higher than those of T2,respectively.The total number of root hairs,root hair density,root hair length and deformed root hair number of vegetable soybean under two nitrogen forms during low nitrogen stress were sig⁃nificantly increased,and the initial distance of root hair was significantly shortened.The root MDA content was significantly reduced.These results indicated that under low nitrogen stress,exogenous chitosan can promote the formation and growth of root hairs,and then promote rhizobium infection,which may be one of the important rea⁃sons for improving the nodulation ability of vegetable soybean under low nitrogen stress.Chitosan promotes the growth of root hairs of vegetable soybean under low nitrogen stress,which may be due to its alleviation of root membrane lipid peroxidation.