Influences of arbuscular mycorrhizal fungi on growth and nutrition of tobacco seedlings under different fertilizer levels

Tobacco seedlings were inoculated with and without arbuscular mycorrhizal fungi(AMF)at the sowing stage and grown in the culture boxes floating on the nutrient solutions to investigate the possibility of producing mycorrhizal and healthy seedlings. AMF used in the present experiment were Glomus intraradices Smith and Schenck(BEG193）and Glomuse etunicatum Becker and Gerdemann(BEG168). The results show that the colonization rate of BEG193 is significantly higher than that of BEG168, and both of them are increased as the concentrations of nutrients in solution are decreased. The growth of tobacco seedlings is also increased significantly by the fungal inoculation, but is inhibited generally in solution with low nutrient concentrations. The average biomasses are increased by 7438%(BEG168)and 4832% (BEG193), respectively, compared to the control(without inoculation). The phosphorus concentration in the seedlings are increased with BEG193 inoculated, and the contents of nitrogen, phosphorus and potassium are increased with BEG168 inoculated. It is necessary to point out that the biomass and contents of phosphorus and potassium in BEG168infected seedlings grown in nutrient solution with 75% of nutrients removed plus small amount of dressing are similar to or higher than those of the nonmycorrhizal ones cultured in the normal nutrient solution. Healthy tobacco seedlings could thus be produced by BEG168 inoculation grown in nutrient culture solution with less fertilization, by which could reduce greatly the amount of fertilizer for seedlings culture and alleviate environmental pollution produced by nutrient solution abandoned. Moreover, under the inoculation of AM the activities of phosphase are increased in the culture medium, and are enhanced as the amount of nutrient supplies is deceased. Therefore, the inoculation of AM could promote the utilization of organic phosphorus in the culture medium and resulted in the increment of phosphorus concentration in tobacco seedlings.