Study On Eco-physiological Adaptation Of Dolichomitriopsis Diversiformis (Mitt.)Nog. Under Desiccation Stress

Bryophytes which is a kind of drying without dying resurrent plant has very strongdesiccation tolerance. In recent years, some studies proved that most of Bryophytes had been intomolecular mechanism level. But different genus is not the same physiological and ecologicaladaptablity to drought stress, and this diversity could explain the distibution and endangeredmechanism for bryophytes.Dolichomitriopsis diversiformis (Mitt.)Nog is one of the species bryophytes in Eastern Asia,With a small amount of the distribution in fan jing mountain area. It had to be one of theendangerous threaten bryophytes of china, owing to its ecological enviroment was destroyed.Based on preciously reaserch, Dolichomitriopsis diversiformis (Mitt.) Nog have depended onwater environment significantly as hygrocolous moss. So we think that we can discusses itseco-physiological adaptability to reveal the reason of its extinction from desicacation tolerance.With moisture as the basis of stress, this thesis systematically study the infuencephysiological charateristics of Dolichomitriopsis diversiformis (Mitt.)Nog’s in fan jing mountainduring the different dehydration and rehydration from its osmosis protectable ability、chlorophyllfluorescence parameters、CO2gas exchange and reactive oxygen metabolism, and we use thewidespread Plagiomnium acutum of the same wet moss as the comparison of materials,that get to conclusions as below:(1) In different dehydration mode, moisture content alternation under summer sunlight issimilar to changes on silica gel fast desiccation.we finally set the time of Dolichomitriopsisdiversiformis and Plagiomnium acutum to CK、D30、 D60and R30、 R60、 R120Whendehydration. According the variation of them in the same processing; these two mosses moisturecontent stablilize when dehydrate1hour and rehydrate2hours. But in the process of dehydration,Dolichomitriopsis diversiformis (Mitt.)Nog’Amplitude of water loss bigger than Plagiomniumacutum, and down89%when rehydrate60minutes. That demonstrates the abilityies ofDolichomitriopsis diversiformis (Mitt.)Nog was worse than that of Plagiomnium acutum, whatreflected its simple tissue that make it established the water potential gradient with the externalenvironment to loss water swift.(2) With moisure content changed, permeability of Plagiomnium acutum sustained a stable lower level. In the procedure of desiccation and rehydration, malondiadehyde (MDA) of bothbryophytes displayed opposite trends of moisture content alternation, that is to say, increasedunder desiccation and then decreased under rehydration, and content in Dolichomitriopsisdiversiformis (Mitt.)Nog was obviously higher than that in Plagiomnium acutum. Duringdehydration and rehydration, superoxide anion (O-2) reproductive rate and hydrogen peroxide(H2O2) content of both species manifested a tendency similar to MDA content, and their value inDolichomitriopsis diversiformis (Mitt.)Nog was obviously higher than that in Plagiomniumacutum. Induced by ROS, activities of antioxidative enzymes of both bryophytes, such assuperoxide dismutase (SOD), catalase (CAT) and ascorbic peroxidase (APX) manifested thesame tendency of ROS alternation, in other words, possessed a peak during dehydration andrehydration, and their activities in Dolichomitriopsis diversiformis (Mitt.)Nog was much moresensitive to dehydration oxidative stress. Ascorbic acid (AsA) contents were raised after the firstdecline, and AsA content of Dolichomitriopsis diversiformis (Mitt.)Nog obviously lower thanthat in Plagiomnium acutum. So totoally, drought will make them stress to oxidative and lipidperoxidation. They can induce stronger antioxidant system through a large number of oxygenburst to decrease membrane lipid peroxidation, However, the removal rate of active oxygen forDolichomitriopsis diversiformis (Mitt.)Nog is still higher than Plagiomnium acutum.(3) the proline and the soluble reducing sugar of these two mosses shows decline after thefirst raised. In the process of dehydration and rehydration, the proline accumulated ofDolichomitriopsis diversiformis (Mitt.)Nog higher than that in Plagiomnium acutum. But thesoluble reducing sugar was opposite. That indicates Plagiomnium acutum Can rely on its strongability of degradation of soluble reducing sugar molecules to repair the cell membrane, but theMembrane systems of Dolichomitriopsis diversiformis (Mitt.)Nog is more easily affected by theaccumulation of proline.(4) In the procedure of desiccation, Plagiomnium acutum could menifested a dramaticdecline and decreased to about400μmol/m2s, in D60min, ETR value of Plagiomnium acutumcould be from10to0, but ETR value of Dolichomitriopsis diversiformis (Mitt.)Nog could beinhibited to null. Fv/Fm, Y(II), qP, Pn, Cond、Ci of both two brophyta species displayed a droptrends, nevertheless, Plagiomnium acutum contain a higher value. NPQ of two bryophytesmenifested an obvious peak, and the peak of Plagiomnium acutum occured early and possess a higher alternative range. Pn and Cond of Dolichomitriopsis diversiformis (Mitt.)Nog get higherthan Plagiomnium acutum, and Ci get lower than Plagiomnium acutum. In the process ofrehydration, inhibit light intensity and ETR value of both species recover rapidly, andDolichomitriopsis diversiformis (Mitt.)Nog menifested slowly and was provide with lessalternation. qP and NPQ of both species recover to normal state, but Fv/Fm and Y(II) were lowerthan control.Pn、Cond、Ci were recover gradually. But when R120, Cond of Plagiomnium acutumwere decline. The above results show that the PS Ⅱ reaction center (P680) pigment ofDolichomitriopsis diversiformis (Mitt.)Nog which Photosynthetic "sleep" time is earlier thanPlagiomnium acutum that is relatively sensitive to drought stress on the dehydration. combinedwith the active oxygen metabolism, we found it has a direct relationship with disorderd SODactivity of protective enzyme system especially in the process of dehydration and rehydration.