外源激素对紫花苜蓿种子内生根瘤菌增殖及幼苗生长的影响OA北大核心

The formation,development,and seedling growth of alfalfa nodules are regulated by multiple plant hormones.The proliferation and growth promoting effects of hormones on exogenous rhizobia have been studied,but there is relatively little research on the proliferation and growth promoting effects of hormones on endogenous rhizobia.To address this knowledge gap,three concentrations of 3-indoleacetic acid(IAA),6-benzylaminopurine(6-BA),and 28-homobrassinolide(HBR),which promote the growth of rhizobium SM12531f,were evaluated.Alfalfa seeds containing cyan fluorescent protein labeled endophytic rhizobia SM12531f were soaked in solutions of one of these three concentrations,and planted.The effects of the exogenous hormones on the number of endophytic rhizobia in alfalfa plant tissue,plant nodulation,and plant growth were analyzed.The results showed that the optimal concentrations for promotional activity of these three hormones were 14 mg·L-1 for IAA,18 mg·L-1 for 6-BA,and 2.97 mg·L-1 for HBR.During the seedling stage,6-BA and HBR were beneficial for the proliferation,nodulation,and growth of endophytic rhizobia in plants,and the former had a more significant growth promotion effect.The hormone 6-BA resulted in the highest number of endophytic rhizobia colonizing in the roots,with a colony density of 1167 cfu·g-1 at a dilution of 100 times and aboveground fresh weight of 1.99 g·plant-1.6-BA was also beneficial to plants during the branching stage.The endophytic rhizobia formed 833 cfu·g-1 in plants with an aboveground fresh weight of 5.03 g·plant-1,when diluted 100 times in a ground root solution.Therefore,in these test conditions,the most suitable hormone for promoting proliferation and growth of alfalfa endophytic rhizobia was 6-BA at 18 mg·L-1 concentrration.These results provide a theoretical basis for the precise utilization of the nodulation nitrogen fixation effect of endophytic rhizobia in seeds,and lays a foundation for the symbiotic breeding of alfalfa rhizobia.