Mechanism Of The Promotion Of Drought Resistance Of Pinus Tabulaeformis Carr. With ECMF

In this paper, a drought-resistant ectomycorrhizal fungi was selected in pure culture, and its phytohormone excretion in mycelium was measured under different drought stress. Pot culture experiments were carried out to study the inoculation effects with the ECMF on the growth and some physio-biochemical indexes of Pinus tabulaeformis Carr.seedlings under drought stress using treatments of different PEG 6000 concentrations in 1/2 Hoagland liquid. In addition, protein expression in ECMF, mycorrhizal plants and non-mycorrhizal plants under different drought stress was analysed. Mechanism of the promotion of drought resistance of Pinus tabulaeformis Carr. with ECMF was revealed. The results were as follows:1. Selection for a drought-resistant ECMFThe growth characteristics of three kinds of ECMF under PEG stress in pure culture were studied, and the results showed that the growth models of the three ECMF were not affected by PEG stress, but the growth rates and biomass changed. Lower PEG concentration(10%) could stimulate the growth of them. Inhibitory efficiency became higher with the increasing PEG concentration(15%~35%). Their resistance to drought were: Suillus laricinus(Berk.in Hook.)O.Kumtze>Suillus tomentosus(Kauff.)Sing.Snell & Dick>Aminita vaginata(Bull.:Fr.)Vitt.2. Phytohormone excretion under PEG stressSuillus laricinus was cultured in MMN liquid stressed with different concentrations of PEG, and the results showed that with the increasing drought stress(0%~25%), the content of gibberellin(GA) and auxin(IAA) in mycelium reduced from 26.53μg/g to 0μg/g and 180.98μg/g to 0μg/g. S. laricinus accumulated the most abscisic acid(ABA)at 15% PEG concentration, 184.36μg/g; when drought stress was beyond the tolerance of S. laricinus(20% PEG concentration), it inhibited the accumulation of abscisic acid(ABA).3. Inoculation effects on Pinus tabulaeformis Carr.S. laricinus significantly promoted the plant hight, stem diamter, plant dry weight and root top rate of P. tabulaeformis, which in mycorrhizal plants was higher by 26.36%, 8.47%, 103.85% and 36.84% than that in non-mycorrhizal plants. And there was no significant difference between the content of relative water. The mycorrhizal dependence was more than 200%, which belonged to medium dependence.There was no significant difference between physiological index of mycorrhizal and non-mycorrhizal plants in normal.4. Effects of ECMF on antioxidant enzyme of P. tabulaeformis under PEG stress SOD and CAT activitiesof mycorrhizal and non-mycorrhizal plants under PEG stress were determined, and the results showed that with increasing duration, SOD activities of mycorrhizal and non-mycorrhizal plants, together with CAT activities at 30% PEG concentration presented descend-ascend-descend trend; CAT activities of other treatments presented ascend-descend trend. SOD activities in mycorrhizal plants were significantly higher than that in non-mycorrhizal plants at 1, 2 and 4 hour stress; and there was no significant difference between them at 8 and 12 hour stress.The highest CAT activities occurred at 2 h of 20% PEG concentration, which in mycorrhizal plants(increased 3.20 times) were higher by 69.50% than that in non-mycorrhizal plants(increased 2.84 times).5.Effects of ECMF on MDA content and membrane permeability of P. tabulaeformis under PEG stressMDA content and membrane permeability of mycorrhizal and non-mycorrhizal plants under PEG stress were determined, and the results showed that MDA content increased by degree with increasing PEG concentration and duration. Root conductivity fluctuated. MDA content between mycorrhizal and non-mycorrhizal plants had no significant difference at 1 hour stress, but it was significantly lower in mycorrhizal plants than that in non-mycorrhizal plants from 2~12 h. MDA content reached the summit at 12 h of 30% PEG concentraiton, and the content in non-mycorrhizal plants were higher by 38.13% than that in mycorrhizal plants. Relative conductivity of non-mycorrhizal plants was higher than that in mycorrhizal plants.6. Effects of ECMF on Pro content of P. tabulaeformis under PEG stressPro content of mycorrhizal and non-mycorrhizal plants under PEG stress was determined, and the results showed that Pro content presented ascend-descend trend with increasing duration. Pro content in mycorrhizal plants was higher than that in non-mycorrhizal plants from 1~2 h, and it was opposite from 4~12 h. Pro content achieved the peak at 4 h, which in non-mycorrhizal plants at 30% PEG concentration (85.60μg/g) was higher by 50.12% than that in mycorrhizal plants.7. Effects of ECMF on wilted coefficient and drought-resistant level of P. tabulaeformis under PEG stressThe wilted coefficient and drought-resistant level of mycorrhizal and non-mycorrhizal plants under PEG stress were determined, and the results showed that wilted coefficient and drought-resistant level increased with increasing PEG concentration and duration. Mycorrhizal plants reached the same damaging degree later than non-mycorrhizal plants. Or mycorrhizal plants appeared the same damaging degree under greater drought stress compared with non-mycorrhizal plants. Non-mycorrhizal plants had a faster and more serious wilting than mycorrhizal plants. In conclusion, in enhanced drought resistance of P. tabulaeformis after inoculating with ECMF.8. Protein expression of ECMF and P. tabulaeformis under PEG stressFrom the SDS-PAGE electrophoretogram, it was observed that ECMF, mycorrhizal plants and non-mycorrhizal plants had different protein bands under drought stress. Protein expression was related to drought strength. More protein(66.2 KDa and 28.4 KDa)was expressed with increasing PEG concentration in mycelium, and no protein was expressed at 30% PEG concentration. Compared with non-mycorrhizal plants, mycorrhizal plants increased the expression of 97.5 KDa protein, besides expressed a more 66.2 KDa protein, and not expressed 13.0 KDa protein. There was no significant difference for protein(14.5 KDa~20.1 KDa)between mycorrhizal and non-mycorrhizal plants.