In a comparison between the three b

In a comparison between the three bioextracts, Chinese kale (or its bio-extract), Chinese cabbage and soybean, the soybean bio-extract with a greater nutrient content (Table 1) produced better growth enhancement. This outcome might be associated with the composition of the available nutrients in the soybean bio-extract suitable for the growth of Chinese kale (Machlis and Torrey, 1965). However, the quantity of nutrients in the soybean bio-extract was quite low and insufficient to support plant growth. In addition, soybean may contain some specific groups of microorganisms that can promote plant growth as plant growthpromoting bacteria (PGPB). Several investigations reported that PGPB can produce plant growth regulators, such as indoleacetic acid (IAA), gibberellic acid, cytokinins and gaseous phytohormone (ethylene) (Ahmad et al., 2008). Moreover, some groups of PGPB can fix nitrogen gas, dissolve unavailable phosphate and produce
siderophore as an iron chelator, as well as deter plant pathogens (Compant et al., 2005).