Effects of Microbial Agents on Growth and Development of Tobacco Seedlings at Seedling and Root Extending Stages

Abstract

【Objective】This study aims to explore the effects of Bacillus siamensis EM-1 and Pseudomonas rhodesiae MTD4-1 on the growth and development of tobacco seedlings at the seedling stage and root extending stage.【Method】Two microbial agents were added to the seedling substrate respectively to study their effects on the microbial diversity of rhizosphere seedling substrate and tobacco seedings root, as well as the morphological and physiological indexes of tobacco seedlings.【Result】Compared with control, the addition of EM-1 bacterial agent could significantly promote the microbial diversity of rhizosphere seedling substrate and tobacco root system at seedling stage, with the increase rates of 9.40% and 34.70%. During this stage, EM-1 bacterial agent can also significantly improve the phenotype and physiological indexes of tobacco seedlings. Compared with the control, its root dry weight, total root length, total root surface area, average root diameter, total root volume, shoot dry weight, seedling height, stem diameter, maximum leaf length, maximum leaf width, root activity, chlorophyll a and total chlorophyll content at the seedling stage increased by 68.81%, 42.55%, 58.08%, 10.10%, 75.83%, 36.27%, 46.63%, 33.56%, 31.10%, 37.97%, 27.04%, 40.00% and 32.14%, respectively. Similarly, the addition of MTD4-1 bacterial agent could also significantly promote the microbial diversity of tobacco root system at seedling stage, with the increase rates of 9.59%. MTD4-1 bacterial agent can also significantly improve the phenotype and physiological indicators of tobacco seedlings at root spreading stage. Compared with the control, the root dry weight, total root length, total root surface area, shoot dry weight, seedling height, stem diameter, maximum leaf length, and maximum leaf width at root extending stage increased by 45.35%, 118.94%, 65.89%, 27.12%, 34.56%, 23.90%, 26.58% and 32.94%, respectively. Correlation analysis showed that a significant correlation between the root microbial diversity of tobacco seedlings and the microbial diversity of rhizosphere seedling substrate, total root length, average root diameter, chlorophyll a and total chlorophyll content of tobacco seedlings (P < 0.05). There was a highly significant correlation between root microbial diversity and total root surface area and total root volume (P < 0.01). The total root length of tobacco seedlings was significantly positively correlated with the total root surface area and chlorophyll content (P < 0.01).【Conclusion】EM-1 bacterial agent mainly promotes tobacco seedling growth by increasing the diversity of tobacco rhizosphere microorganisms at the seedling stage, while MTD4-1 bacterial agent mainly promotes tobacco seedling growth by increasing the diversity of tobacco rhizosphere microorganisms at the root extending stage. The quality of tobacco seedlings during the seedling cultivation period and after transplantation will be improved by adding EM-1 and MTD4-1 into substrate respectively.

Keywords

• microbial agents
• microbial diversity
• tobacco seedling
• root development
• root activity
• leaves pigment