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| Effect of Methylotrophic Bacillus on Growth and Element Accumulation for Cucumber Plug Seedling |
| MA Fei1，2，3，WANG Jing1，2，3，WANG Junzheng1，2，3，HU Xiaohui1，2，3* |
| 1College of Horticulture，Northwest A & F University，Yangling 712100，Shaanxi，China；2Key Laboratory of Protected Horticultural Engineering in Northwest，Ministry of Agriculture and Rural Affairs，Yangling 712100，Shaanxi，China；3Facility Agriculture Engineering Technology Research Center of Shaanxi Province，Yangling 712100，Shaanxi，China |
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Abstract In order to explore the effect of different dosages of methylotrophic bacillus inoculants on cucumber plug seedlings and its regulation mechanism，and to screen optimal dosage，this paper took ‘Bonai 526’ cucumber as test material；studied the effects of different concentrations of methylotrophic bacillus mixed in substrate on morphological development，biomass，chlorophyll content，element accumulation，root system morphology and root system hormone content of cucumber plug seedlings．The results showed that comparing with seedlings under treatment without applying aseptic agent（CK），applying methylotrophic bacillus could significantly improve the morphological indicators of cucumber seedlings．T2-T5 treatments had significantly increased the biomass，strong seedling index，and growth function（G value） of cucumber seedlings．The increasing rage were 58.0%-70.6%，3.2%-24.2% and 56.1%-75.6%，respectively．The chlorophyll content of seedling leaf blades decreased first，then increased with the increase of inoculant dosage．The increasing rage of T4 treatment was significantly higher than that of the other treatments．The total chlorophyll content had increased 23.9% comparing with the CK．Applying methylotrophic bacillus increased the contents of auxin acid（IAA） and jasmonic acid（JA）in seedling root system；reduced the ethylene level；promoted the increase of cucumber root length，root surface area，root diameter，root volume and root tip number to varying degrees，and also increased the accumulation quantity of plant N，P，K elements．As you see，methylotrophic bacillus could promote root system growth；and then enhance the absorption，assimilation and material accumulation of elements；affect the content of chlorophyll，and comprehensively regulate the growth and development of cucumber seedlings. Besides，its effect could be regulated by dose．Medium and high-dose treatments（T3，T4 and T5） had overall better effects on morphological development，physiological metabolism，element absorption and dry matter accumulation than low-dose treatments（T1 and T2）．Considering the effects and production costs by different use level of inoculants，it is recommended to add 15 kg · m-3 of methylotrophic Bacillus inoculum（5 × 1010 CFU · g-1） to substrate in factory-like plug seedling culture．
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Received: 14 February 2022
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