| Drought has been one of the most important stress affect plant growth. Microorganism symbiosised with plants through adjusting to the metabolism and physiological active substances of the host and enhancing the adaptability to the environment. To explore the effect of symbiotic microorganisms on plant drought resistant properties, this study used endophytic bacteria isolated from desert plants Lepidium perfoliatumL. belong to the cruciferous root as material, model plant Arabidopsis thaliana as plant material as object, researched the influence of the symbiosis for drought resistance, phenology and seed production of Arabidopsis thaliana, and provide a basis for understanding the symbiotic drought-resistant mechanism. The major results are as follows:Used endophytic bacteria isolated from desert plants Lepidium perfoliatumL. root belong to the cruciferous as material, model plant Arabidopsis thaliana as plant material as object, with different concentrations of polyethylene glycol(PEG) 6000 as stress agents simulated drought conditions, screened the endophytic bacteria has drought-resistant and promote germination for Arabidopsis thaliana, the results confirmed, inoculated endophyte had no significant effect on the germination of Arabidopsis thaliana seeds at concentration 5% PEG; at 10% PEG stress had one strain(NG4-5) allows the seed germination rate of 75% to 85%; at 15% PEG stress had four strains(NG4-1, NG4-2, NG4-4 and NG4-11), respectively make the germination rate increased from 52% to 67.5%, 63.13%, 75% and 59.55%; at 20% PEG stress had one strain(NG4-6) makes the germination rate increased from 31% to 51.5%; at 25% PEG stress had three strains(NG3-6, NG3-10 and NG4-6) make germination rate were increased from 0% to 6.5%, 6% and 20.5%. In which 15% PEG 6000 is the seed germination half inhibitory concentration of stress, in this stress, strain NG4-4 most significant role, so the subsequent test used NG4-4 as experimental material.To understand the manner in which the strain NG4-4 play drought effect, the test separated into its culture supernatant and bacterial cells, the supernatant was directly immersed seeds, bacterial cells were washed with phosphate buffer and resuspended after soaking seeds, and at 15% PEG 6000 stress detection seed germination. The results showed that the strain NG4-4 supernatant significantly promote seed germination(p<0.05), the resuspended cells showed no significant difference(p>0.05), and the mixed culture can significantly improve seed germination rate(p<0.01), confirmed that the strain NG4-4 play the role of promoting the germination and drought-resistant with mixed culture.Research for inoculation of the strain NG4-4 cultures Arabidopsis thaliana physiological characteristics under drought stress indicate that inoculated group(E+) can reduce the plant MDA content 12.65%(p<0.01); and the antioxidant enzymes SOD, CAT and POD were increased, showing endophytic symbiotic by reducing the drought caused membrane peroxidation damage, decomposing the harmful reactive oxygen to alleviate drought stress. And accumulation of proline and soluble protein was increased, indicating endophytic symbiosis can increase osmotic adjustment reduces osmotic potential, improve drought resistance in Arabidopsis thaliana.Research on phenology and seed yield of Arabidopsis thaliana with inoculated and non-inoculated(E-) conditions was displayed, under drought stress, E+ made ahead of the plants bolting, flowering, produce seeds and seed maturation were 2 days, 2 days, 4 days and 4 days, increased the pod length 1.71mm(p<0.01), increased the number of seeds per the pod 5 tablets(p<0.01), increased seed yield per plant 3.452mg(p<0.01); under non-drought stress, E+ made the plants bolting, flowering, produce seeds and seed maturation ahead of 2 days, 6 days, 6 days and 4 days, the average number of pods per plant increased 177.33(p<0.01), seed yield per plant increased 13.252mg(p<0.01). The results showed that endophytic symbiosis both for increasing seed yield role regardless of drought and non-drought.In summary, inoculated endophytic bacteria isolated from desert plants Lepidium perfoliatumL. root promote seeds germination and response of different strains under different degrees of drought stress, which NG4-4 can significantly improved the seed germination rate at 15% PEG, based with the strain mixed culture, and its function mechanism is by reducing the cell membrane peroxidation damage, improve the activity of antioxidant enzymes and accumulation of osmotic adjustment and improve drought resistance in plant. And under drought and non-drought conditions are ahead of Arabidopsis thaliana reproductive phenology, respectively, to increase the number of seeds per pod and pods per plant increased seed yield increases. |
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