Abstract
In this study, we investigated the influence of rhizosphere microorganisms on seed germination and root metabolism in Cerasus sachalinensis Kom. We inoculated C. sachalinensis plants with suspensions of dominant bacterial strains isolated from their rhizosphere. Four bacterial strains each with significant growth-promoting or growth-inhibiting effects were screened from the efficient root-colonizing microorganisms. The number of actinomycetes increased and that of fungi decreased significantly in the seedling rhizospheres after rhizobacteria treatment. The growth-promoting bacteria slightly affected the respiration rates and respiratory pathway enzymes, but significantly improved root viability, root carbohydrate concentration and seedling growth. Bacillus cereus, Staphylococcus sp. and Pseudomonas fluorescens were identified as the growth-promoting rhizobacteria; one strain could not be identified. After inoculation with the growth-inhibiting bacteria, the number of fungal colonies in the seedling rhizospheres increased and root viability and respiration rate as well as starch and sucrose accumulation in the roots significantly decreased. The glycolysis, pentose phosphate and alternative oxidase pathways became the major pathways of respiratory metabolism after inoculation with the growth-inhibiting bacteria. The height, leaf number, growth and dry weight of the seedlings decreased significantly in plants inoculated with the growth-inhibiting bacteria. Inoculation of C. sachalinensis rhizosphere with growth-promoting and growth-inhibiting bacteria affected the soil environmental factors such as microbial group composition, nutrient concentration and seedling biomass.
Highlights
Modification of the plant root system is considered as a means for crop improvement in environments with marginal soils, low-nutrient and droughtprone agricultural areas (MacMillan et al, 2006)
We investigated the influence of rhizosphere microorganisms on seed germination and root metabolism in Cerasus sachalinensis Kom
Rhizosphere microorganisms are an essential part of the soil-plant ecological system; their community structure and activity are affected by soil properties and plant physiological processes, such as root secretions and soil organic matter (Picard & Bosco, 2008; Bulgarelli et al, 2013)
Summary
Modification of the plant root system is considered as a means for crop improvement in environments with marginal soils, low-nutrient and droughtprone agricultural areas (MacMillan et al, 2006). Many studies investigating root development and physiology have not considered the effects of the rhizosphere (Bakker et al, 2013; Philippot et al, 2013). Feedback from the microorganisms in the rhizosphere helps in regulating root function (Wasaki et al, 2005; Allison et al, 2008), influences plant growth and development by producing indole-. Recent studies have mainly investigated the biological relationships between plants and bacteria in the root zone; these relationships can have a positive or negative influence on plant growth (Dary et al, 2010). Elucidating the mechanisms underlying the effects of microorganisms on soil ecology and microbial regulation of plant growth and development are necessary for maximizing soil biological potential and improving plant-production capacity
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