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Effects Of Arbuscular Mycorrhizal On Drought Resistance And Rhizosphere Soil Nutrition In Ceiba Pentandra And Bombax Ceiba

Posted on:2016-08-31Degree:MasterType:Thesis
Country:ChinaCandidate:J J YangFull Text:PDF
GTID:2180330485965397Subject:Forest cultivation
Abstract/Summary:PDF Full Text Request
Bombax ceiba is one representative species in the dry-hot valley, which induces a symbiosis relationship with arbuscular mycorrhizal(AM). This symbiosis is a significant factor in drought adaptation mechanism as well as in the ecological restoration. With Bombacaceae seedling(Bombax ceiba and Ceiba pentandra) of six months cultivation as materials, which inoculated AM or no inoculated AM, used weighing method to control water content in soil. Set up three water gradient: normal control(field capacity 70%-75%), moderate water stress(field capacity 50%-55%) and severe water stress(field capacity 30%- 35%). Here we focus on the effect of growth, photosynthetic physiology, fluorescence parameter changes, osmotic regulation mechanism, soil nutrient and leaf nutrient characteristics to find the drought resistance regulation and nutrient transport rule in the arbuscular mycorrhizal symbiosis. The results showed that:(1) Bombacaceae were sensitive to grown affection under drought stress. The ground diameter, high growth, leave number and biomass reduced with the deepening and time prolonged(1d, 3d, 5d, 7d, 15 d, 25 d, 45d) of drought stress. The ground diameter stopped growing at the beginning of severe drought stress, but moderate drought stress to stop the growth delay 5 day. Strong changes in the severe stress, the “shrinkage” appeared after ground diameter stopped growing, deciduous occurred in the 7th day, and then in the 25 th day the high growth stopped, and in the 45 th day all the leaves fell, and in the 60 th day all the seedlings died. On the other hand, the water content ratio of root, stem and leaf was close to 1:1:1 in normal water control, but the condition of water content changed to leaf > root > stem, leaf had priority to get more water and the water content of leaf maintained between 66% and 80%.(2)There were abvious differences in photosynthetic according to drought stress. With the drought time prolonged, the net photosynthetic rate(Pn), stomata conductance(Gs) and transpiration rate(Tr) were trend to increased and then drop in normal control. But Pn, Gs and Tr significantly reduced with the deepening of drought stress. Pn, Gs and Tr reduced at first, and then increased, and decreased at last in moderate or severe stress. Despite the seedling could self-adapt at the begining, but the regulating mechanism broke with stress prolonged, the Pn dropped. The The Pn of B. ceiba were higher then C. pentandra, and the peak of Pn occurred in the 7th day, the maximum of Pn in C. pentandra and B. ceiba were 35.94 μmol/m2·s and 41.74 μmol/m2·s.(3)The electron transfer rate(ETR) and quantum yield of regulated energy dissipation(Y(NPQ)) reduced gradually in the early time, but the parameters of Bombacaceae could keep maximal PSⅡquantum yield(Fv/Fm) between 0.63 and 0.77 and PSⅡquantum yield(Fv/Fo) at a higher level, and coefficient of photochemical quenching(qP) improved and the dissipative coefficient of nonphotochemical quenching(qN) enhanced, quantum yield of non-regulated energy dissipation(Y(NO)) also increased with the drought stress intensity increasing, thereby avoiding PSⅡ to produce light oxidation or photoinhibition, these were the photosynthetic characteristics in drought resistance of Bombacaceae. At the late stage of drought, Fv/Fm and Alpha dropped, PSⅡ potential activity was inhibited, electron transfer rate reduced. When the proline and amino acid increased, the qN and Y(NO) also increased to avoid the PSⅡ injured from the dark fluorescence yield(Fo). MDA could injure physiological system, but proline could protect physiological system. Under severe stress, the peak of MDA in C. pentandra and B. ceiba were 36.24μmol/g FM and 23.54μmol/g FM, and the time to reach the peak points were MDA > free proline > free amino acid, we found the peak of MDA and amino acid content in C. pentandra were higher than B. ceiba, and B. ceiba was injured later than the C. pentandra, suffered less damage than C. pentandra.(4)With the drought time prolonged in normal control and moderate stress, total nitrogen(TN), NO3-N, soil available phosphorus(AP) and AK increased, and total phosphorus(TP) increased and then decreased, but changes in content of total phosphorus(TK) were contrary to the TP. Soil TN, TP, TK, NH4-N, AP and AK reduced gradually with drought stress intensity increasing. Absorption of nitrogen increased in root as well as nitrogen, phosphorus and potassium increased in leaves. The changes of N, P and K content in leaves depend on the nitrogen content in roots. From the perspective of nutrient elements distribution in different organs, phosphorus and potassium was stem > root > leaf; and the distribution of the nitrogen was different, Ceiba pentandra were leaf > stem > root, Bombax ceiba were stem > leaf > root. Moderate stress and severe stress phosphorus content in different organs were higher than normal water control, the field capacity highest phosphorus uptake of soil water between 12.4% and 13.8%. High potassium content in leaf was probably one of the nutritional characteristics in drought resistance of Bombacaceae.(5)Severe drought treatment infection rates fell; the drought affected the mycorrhizal formation. Moderate stress on the mycorrhizal dependencies as high as 50.55% in C. pentandra, and normal water control mycorrhizal dependency was 45.15% in B. ceiba. The relative yield also changed the mycorrhizal dependency.(6)Mycorrhizal formation of Bombacaceae was an important mechanism to adapt to the climate dry-hot valley. Inoculation of AM fungi could speed up the growing rate, increase leaf number, delay the time of growth stop and leaf fall-down, and significantly increace the biomass. Compred with normal control, the inoculation of AM fungi could promote the increase of Pn, Gs and Tr. Under the same water treatment, and promote electron transfer rate in the center of PSⅡand improve electron transfer activity to improve photosynthetic ability, in addition AM could improve the Fm, Fm’, Fv/Fm, Fv/Fo and alpha, but were not conducive to improve qN, Y [NPQ] and Y [NO]. Inoculation of AM fungi could reduce the MDA and amino acid content, and improve the proline content, so as to reduce the degree of damage, enhance the active oxygen removal, thereby protecting the membrane system. Under the same water treatment, The TN, TK, NH4-N, NO3-N, AP and AK content of the soil inoculated with AM fungi were higher than the treatments without inoculation. Inoculation of AM fungi could increase the phosphorus content and nitrogen content in root.To sum up the results: the drought was main factor, which leading to reduce the growth, photosynthesis and nutrient change. Those changes wreaked according to inoculate AM, such action were based on improving the moisture content, increasing ETR and qP and decreasing MDA and free amino acids; AM fungi also improved plant nutrition levels, so that improving drought resistance of host plants.
Keywords/Search Tags:Drought stress, Arbuscular mycorrhizal, Ceiba pentandra, Bombax ceiba, Growth, photosynthesis, fluorescence parameter, Soil nutrition
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