Fig. 2. Schematic of coated seeds (left) and uncoated seeds (right)

Water

PBM such as Azotobacter chroococcum and Azospirillum brasilense in Mentha pulegium(Asghari et al. 2020), Pseudomonassp. and Azotobacter sp. in Cymbopogon citratus(Mirzaei et al. 2020) can promote plant tolerance against drought stress. Increased soil temperature by water stress can inhibit PBM multiplication. In addition, it has been reported that flooding condition causes the reduction of O2availability in the soil and restricts the aerobic respiration of microorganisms in soils (Enebe and Babalola 2018). The type of microorganism and light intensity can influence PBM efficiency (Lopes et al. 2018).

Light

Light may alter the interactions between plants and micro-organisms by changing the quantity and chemical compound of root exudates (Lopes et al. 2018). The colonization of microorganisms depends on plant-provided carbohydrates in exchange for nutrients. Under limited light intensity, inoculation of PBM such asKaistobacter sp. and Pseudomonas sp. can enhance the growth of Ophiopogon japonicus and Lolium perenne(Fu et al. 2020). The microbial root symbioses such as Paraglomus sp., Rhizophagus sp., andRhizobium inhibited the growth of Phaseolus lunatus(Ballhorn et al. 2016).

Temperature

Temperature can interfere with interactions between plants and microorganisms by changing root exudation composition, as well as, affecting the morphological, biochemical, and physiological attributes of plants (Meena et al. 2015). Inoculation of PBM such as Pseudomonas putida and Bacillus cereus can increase the growth of Triticum sp. and Solanum lycopersicum and decrease the negative effects of high-temperature stress (Ali et al. 2011). Similarly, it has been found that the inoculation of Burkholderia sp. increased the tolerance and yield of Vitis vinifera under low temperatures (Fernandez et al. 2012).