| Affected by the variation of global climate,precipitation distribution has been changing in many regions especially in southwest China,recent years,drought occurred more and more frequently,which has a significant impact on the growth and development of the main local industrial crop,the tobacco.Research shown various kinds of physiological and biochemical metabolism process of tobacco can be affected by drought,such as photosynthesis,respiratory metabolism,absorption and translocation of water and nutrient elements,activity of many kinds of enzyme,conversion and accumulation of organic substance etc.Defect like crimp and shrinkage of the leaves also can be caused by drought stress,thus the productivity and quality can be lowered seriously,as a result,the local economy development will suffer a huge damage.Mycorrhiza is a symbiotic system formed by the root of higher plant and soil fungi,this kind of symbiotic system is ubiquitous in the nature,among those,as the kind with the most suitable parasitifers and the closest relationship with agricultural production,Arbuscular Mycorrhiza(AM)is named for its ability of forming arbuscular structure on the root cortex of plants.The resistance of stress and disease of the parasitifer can be improved by AM for its ability of absorbing water and mineral nutrition directly,enlarging the absorption range of the root,improving the water metabolism and nutritional condition,improving the growth of parasitifer and inducing the expression of defense gene.This study is composed of two experiments,in the first one,the main tobacco varieties Yunyan87 and Hongda are selected as the research objects to study the growth promotion effect caused by inoculating AM to different tobaccos and the differences between the construction of symbionts formed by AM and different parasitifers,and analyze the effect on the form of tobacco roots and absorption of mineral nutritions.In the second one,Hongda is selected as the research object,during the study the effect of AM during the process of drought resisting is studied,the the role AM plays in the process of drought stress and artificial irrigation is revealed by drought and re-watering treatment.From this study theoretical basis in the application of Mycorrhiza against drought stress can be offered.Main results are listed below:1.Stable intergrowth structure can be detected on the roots of Yunyan87 and Hongda after AM(Glomus intraradices BGC BJ09)is inoculated,analysis of variance shown infected percentage of mycorrhiza on Hongda is significantly higher than Yunyan87.2.Inoculation of AMF plays a positive role in growth-promoting effect on both tobaccos,significant improvement of both the ground and underground biomass can be detected,however the growth promoting effect on Hongda is higher than that is on Yunyan87,test shown after inoculation,the increase of ground and underground biomass of Hongda is 46.02%and 37.82%respectively,compared with 28.33%and 20.49%of Yunyan87,the root surface-area of both tobacco shown a significant increase also.What’s more,the absorption of P is improved after AMF is inoculated,however the absorption of the other mineral element like C,N,S,K,Mg and Ca shown no difference.3.Drought and re-watering test was adopted on Hongda,results shown drought condition helped to improve the infection rate,but won’t influence the chlorophyll content;On the other hand,dry treatment lowered the biomass and root phosphor concentration significantly;after the treatment of re-watering,the proline concentration was lowered significantly.4.The net photosynthetic rate of tobacco was lowered significantly after drought treatment,but no significant effect can be detected after the inoculation of AMF.After re-watering treatment,the net photosynthetic rate of inoculated tobacco is higher than the tobacco without AMF.5.After drought treatment that was significant lowered.After inoculated by AMF,the stomatal conductance under the same drought treatment is lower than control group,while under the same re-watering treatment that is significantly higher than control group.6.After drought treatment,the transpiration rate was lowered with a trend of continuous declination along with the extension of drought time,no significant impact on the transpiration rate of tobacco can be detected after inoculation.7.The intercellular concentration of CO2 can be significantly lowered after drought treatment,that is still higher than control group the first day after inoculation,no significant impact on the intercellular concentration of CO2 caused by AMF inoculation can be detected with the extension of drought time,but after the re-watering treatment,the intercellular concentration of CO2 is significantly higher with AMF inoculation. |
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