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The Effects Of Drought And Enhanced UV-B Radiation On Physiological Metabolism And Antioxidant Isozyme Of Lespedeza Davurica

Posted on:2015-11-22Degree:MasterType:Thesis
Country:ChinaCandidate:C H CaiFull Text:PDF
GTID:2180330434460230Subject:Botany
Abstract/Summary:PDF Full Text Request
The effects of different drought intensity (55%±5%,35%±5%of field capacity), differentUV-B radiation intensity (1.944KJ m-2d-1,1.3.002KJ m-2d-1) and their combined treatmenton biomass and biomass allocation, nitrogen metabolism, contents of UV-B absorbingcompounds, antioxidant isoenzyme in Lespedeza davurica were investigated under controlledconditions. The main objective of the study is to explore the adaptation strategies ofLespedeza davurica to drought and UV-B radiation, in order to provide a theoretical basis forfurther revealing the mechanism of interaction effect between drought and enhanced UV-Bradiation. The following conclusions:1、The effects of drought stress and enhanced UV-B radiation on biomass and biomassallocation in Lespedeza davuricaUnder drought stress, stem biomass, leaf biomass and total biomass were inhibited, whileroot shoot ratio increased with the drought stress intensity increasing. Enhanced UV-Bradiation reduced the accumulation of organs’ biomass and total biomass. Low-intensityUV-B radiation alleviated the inhibitory effect of leaf biomass, stem iomass and total biomasscaused by drought stress, however high-intensity UV-B radiation exacerbated the inhibition oforgans’ biomass and total biomass caused by drought stress. Viewing the point of biomassallocation, under enhanced UV-B radiation and its combined treatment with drought stress,root allocation decreased, while the allocation of stem and leaf increased with UV-B radiationintensity increasing, root shoot ratio was reduced at the same time.2、The effects of drought stress and enhanced UV-B radiation on nitrogen metabolism inLespedeza davuricaAt the early stage of mild drought stress, Lespedeza davurica showed a certainadaptability to drought stress, in which the activitives of NR, GS, GOGAT, GDH increased,with drought time prolonging and drought intensity increasing, nitrogen metabolic activitydecreased, and endopeptidase activity rapidly increased. The contents of free proline andsoluble protein increased first and then decreased under drought stress. Enhanced UV-Bradiation effectively alleviated the inhibition effects of drought stress on nitrogen assimilationof Lespedeza davurica by increasing the activities of NR, GS, GOGAT, GDH. What’s more, enhanced UV-B radiation increased the accumulation of soluble protein. However, when theintensity of drought and UV-B radiation increased, Lespedeza davurica nitrogen metabolismwas limited.3、The effects of drought stress and enhanced UV-B radiation on contents of UV-B absorbingcompounds in Lespedeza davuricaUnder drought stress, the contents of flavonoids and total hydroxybenzene increased.Under UV-B radiation, the contents of flavonoids and total hydroxybenzene, PAL activityincreased with UV-B radiation intensity increasing. Enhanced UV-B radiation promoted theaccumulation of flavonoids, total hydroxybenzene under drought stress. Compared with othercombined treatments, the contents of flavonoids and total hydroxybenzene, PAL activityincreased more significantly under the combined treatment of mild drought stress andenhanced UV-B radiation, meanwhile, at the later stage, UV-B absorbing compoundssynthesis efficiency decreased under all treatments.4、The effects of drought stress and enhanced UV-B radiation on Antioxidant isoenzyme inLespedeza davuricaThe SOD isoenzyme activity did not significantly increased under drought stress, butsome of them increased under enhanced UV-B radiation. CAT isozyme activity was lower atdrought stress early stage compared with control, but with the treatment time processing, itsactivity gradually increased, and was stronger than that under control at later stage. At droughtstress early stage, POD isoenzyme activity increased with stress levels increasing, andemerged a new enzyme bond. At drought stress later stage, POD isoenzyme activity washigher than that under control, but gradually weakened under severe drought stress, andeventually fell to the control level or below the control level. Under enhanced UV-B radiation,POD isoenzyme activity increased, and appeared four new bands. Under drought stress,enhanced UV-B radiation promoted SOD, POD, CAT isozyme genes expression and enhancedtheir activies, as well as several new bands of POD isozyme emerged. But with the intensityof UV-B radiation increasing, the self-regulation sytem of Lespedeza davurica was damaged,resulting in its metabolism level decreased.In summary, under combined treatment of drought and enhanced UV-B radiation,Lespedeza davurica adapt to combined treatment by increasing the allocation of stem and leaf,that conducive to enhancing photosynthetic carbon assimilation, alleviating the inhibition ofbiomass caused by singe drought sress, and enhanced the nitrogen metabolic processdepending on the photosynthetic carbon metabolism to provide energy and substrate. Underdrought stress, enhanced UV-B radiation by promoting the synthesis of UV-absorbingsubstances and induced expression of a large number of antioxidant enzymes genes to improve antioxidant capacity of Lespedeza davurica, thus slowing the damage caused bysinge drought to Lespedeza davurica. However, when drought and UV-B radiation is moreserious, the self-regulation sytem of Lespedeza davurica will be damaged, resulting in itsmetabolism level decreased.
Keywords/Search Tags:Lespedeza davurica, Drought stress, Enhanced UV-B radiation, Physiological metabolism, Antioxidant isoenzyme
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