Effects of different microbial agents on the morphogenesis and physiological characteristics of rice seedlings

【Objective】The study was conducted to investigate the effects of different microbial agents on the morphogenesis and physiological characteristics of rice seedlings，enrich the study of microbial bacterials in rice growth and it also provided theoretical basis for high quality and efficient cultivation of rice.【Method】Rice variety Haihong 12 was employed as the experimental material to conduct pot experiment. The rice seedlings were irrigated with 100 mL of five kinds of microbial bacterials［Bacillus pumilus（BP），Rhodotorula and Saccharomyces cerevisiae mixture（RS），B. subtilis （BS），B. natto（BN），B. amyloliquefaciens（BA）］with 1% concentration at 1 leaf /1 heart，100 mL clear water was as control（CK）. The morphological characteristics，superoxide anion production rate（O₂^-·），activities of antioxidases，malondialdehyde（MDA）and soluble protein content of Haihong 12 seedlings were studied at the stage of 4 leaves after root irrigation.【Result】The results showed that compared to the CK，five exogenous microbial agents could promote the growth of Haihong 12 seedlings and significantly（P<0.05，the same below）increased the plant height，shoot dry weight，root surface area and root volume of Haihong 12 by 4.9%-18.4%，23.3%-44.2%，44.5%-86.6% and 75.0%-175.0%，respectively， among which BN had the best effect. BS and BA were better for SPAD of Haihong 12 seedlings than those treated with other microbial agents，but exogenous microbial agents treatments had no significant difference with CK（P>0.05）. BP， BS，BN and BA treatments could increase the soluble protein content and the activities of superoxide dismutase（SOD）， peroxidase（POD），the increase reached 5.6%-17.8%，61.1%-126.7%，66.1%-117.9%，respectively. BP，BS and BN treatments could significantly improve the activities of catalase（CAT），the increase reached 17.6%，29.7%，21.6%，respectively. BN treatment could increase improve the activities of ascorbate peroxidase（APX），the increase reached 112.8%， among which BS and BN had a better regulation effect. Furthermore，BP，BN and BA treatments significantly decreased MDA content in leaves，the reduction reached 11.8%-16.6%. O₂^-·production rate of leaves treated with BP and BN significantly reduced by 53.2% and 42.9%，respectively.【Conclusion】The promotion effects of microbial agents on morphogenesis of Haihong 12 seedlings might be due to the stimulation on plant height，shoot dry weight，root surface area and root volume，and it results in increased resistance to biotic and abiotic stresses throughout raising the activities of antioxidant enzymes，reducing the level of membrane lipid peroxidation，and increasing the accumulation of soluble protein. Among the five agents，the comprehensive regulation effect of BN is the best.