Inoculation with Bacillus licheniformis MH48 to improve Camellia japonica seedling development in coastal lands

This study aimed to determine the promotion of the growth and nutrient uptake of Camellia japonica seedlings in coastal lands by bacterial inoculation. Soil salinity reduces plant growth and development in coastal areas due to the osmotic stress that perturbs nutrient uptake. The soil electrical conductivity at the sites of this study ranged from 1.02 to 1.89 dS m(-1). Application of chemical fertilizer resulted in the limited uptake of nutrients in seedlings under saline conditions as well as a low nutrient content in the soil caused by leaching, with no significant influence on the growth of the seedlings. However, Bacillus licheniformis MH48 increased the total nitrogen and total phosphorus in the soil due to atmospheric nitrogen fixation and the solubilization of phosphorus via organic acid exudation. In addition, B. licheniformis MH48 produces auxin, which stimulates root development and nutrient uptake. The bacterial inoculation could reduce the ethylene levels in seedlings by containing ACC deaminase, thus alleviating salt stress. Thus, bacterial inoculation significantly increased plant biomass to amounts of 15.67 g plant(-1) (the sum of the leaves and shoots) and 8.00 g plant(-1) in the roots of the seedlings. The nutrient uptake by seedlings also improved 2 to 3 times after the bacterial inoculation. The plant development effect appears to be direct, with the possible involvement of the bacterial inoculation as a plant development regulator. In view of environmental pollution due to excessive use of fertilizers and the high cost of producing fertilizers, the bacterial inoculation tested in our study has the potential to be used for environmentally benign plant production. However, the survival rate between the groups decreased due to salt stress. In particular, the survival rate of the seedlings that received bacterial inoculation was not significantly different from that of uninoculated seedlings. C. japonica seedlings are considered moderately sensitive to salinity.