The objective of this study was to determine whether inoculation with Bacillus licheniformis MH48 as a plant growth-promoting rhizobacterium (PGPR) could promote nutrient uptake of seedlings of the ornamental plant Camellia japonica in the Saemangeum reclaimed coastal land in Korea. B. licheniformis MH48 inoculation increased total nitrogen and phosphorus content in soils by 2.2 and 20.0 fold, respectively, compared to those without bacterial inoculation. In addition, B. licheniformis MH48 produced auxin, which promoted the formation of lateral roots and root hairs, decreased production of growth-inhibiting ethylene, and alleviated salt stress. Total nitrogen and phosphorus uptake of seedlings subjected to bacterial inoculation was 2.3 and 3.6 fold higher, respectively, than the control. However, B. licheniformis MH48 inoculation had no significant effect on the growth of seedlings. Our results suggest that inoculation with B. licheniformis MH48 can be used as a PGPR bio-enhancer to stimulate fine root development, promote nutrient uptake and alleviate salt stress in ornamental plant seedlings grown in the high-salinity conditions of reclaimed coastal land.

IntroductionCamellia japonica is a broad-leaf evergreen tree that is naturally distributed in coastal areas of the southern parts of Korea (Park et al., 2017). This tree constitutes an important type of coastal vegetation in Korea because the tree is relatively tolerant to sea breeze and salinity. However, most C. japonica forests in the coastal areas of Korea have been degraded due to human activities such as road construction, urban development, and seedling collections for potted planting. The Korean government has made efforts to restore C. japonica forests in coastal areas, but restoration is very difficult (Park et al., 2017). In coastal environments, plant growth and survival are affected by the salinity of the soil and by the low availability of nutrients (Williams et al., 1998;Weber and D' Antonio, 1999). In particular, excess salt in the soil can decrease plant growth by inhibiting the osmotic uptake of water by roots or by causing nutritional imbalance through competitive ion absorption (Koyro, 2006).Plant growth-promoting rhizobacteria (PGPR) are the rhizosphere bacteria that can enhance plant growth by a wide variety of mechanisms including phosphate solubilization, siderophore production, biological nitrogen fixation, rhizosphere engineering, phytohormone production, and interference with pathogen toxin production. The potentiality of PGPR in agriculture and forestry is steadily increased as it offers an attractive way to replace the use of chemical fertilizers, pesticides, and other supplements (

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Fine particulate matter entering the body through breathing cause serious damage to humans. In South Korea, filter-type air purifiers are used to eliminate indoor fine particulate matter, and there has been a broad range of studies on the spread of fine particulate matter and air purifiers. However, earlier studies have not evaluated an operating method of air purifiers considering the inflow of fine particulate matter into the body or reduction performance of the concentration of fine particulate matter. There is a limit to controlling the concentration of fine particulate matter of the overall space where an air purifier is fixed in one spot as the source of indoor fine particulate matter is varied. Accordingly, this study analyzed changes in the concentration of indoor fine particulate matter through an experiment according to the discharging method and location of a fixed air purifier considering the inflow route of fine particulate matter into the body and their harmfulness. The study evaluated the purifiers’ performance in reducing the concentration of fine particulate matter in the occupants’ breathing zone according to the operation method in which a movable air purifier responds to the movement of occupants. The results showed the concentration of fine particulate matter around the breathing zone of the occupants had decreased by about 51 μg/m3 compared to the surrounding concentration in terms of the operating method in which an air purifier tracks occupants in real-time, and a decrease of about 68 μg/m3 in terms of the operating method in which an air purifier controls the zone. On the other hand, a real-time occupant tracking method may face a threshold due to the moving path of an air purifier and changes in the number of occupants. A zone controlling method is deemed suitable as an operating method of a movable air purifier to reduce the concentration of fine particulate matter in the breathing zone of occupants.

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