Study On Ecophysiologial Mechanism For Adaptation Of Several Psammophytes To Sand Burial

Desertification is one of the major environmental and social issues nowadays, and Chinais a developing country affected by desertification. In recent years, not only in inland aridregion and the semi-arid areas of desertification area up to3436square kilometers due toclimate change. In the desertified region, sand burial caused by flowing habitat affect theplant's settle, reproduction, and vegetation succession. But there are still some psammophytescan sustain their growth. But it is not clear if these plants have some physiological adaptiveresponses can sustain growth under sand buried. In order to reveal psammophytes anti-sandburied in the physiological regulation mechanism and the growth of adaptive responses, richdesert scientific theory, provide the scientific basis of the environmental remediation, desertmanagement and basianti-sand plant's breeding. We selected two advantaged sandy plants:Messerschmidia sibirica Linn, Vitex trifolia var.simplicifolia (beach sand), and Artemisia halodendron, Lespedeza bicolor Turcz (arid sand) as test material in Yantai coast sand and theHorqin sandy land. Basis on the height of plants, the different level of sand burial treatmentswere set up in this study in Yan Tai coastal dune and Horqin sandy land in Spring and summerof2009,2010and2011. The changes in soil temperature, soil moisture, FW, DW, plantrelative height, plasma membrane permeability, MDA content and osmotic regulator andactivity of antioxidant enzymes in the leaves of plants from different level of sand burial wereinvestigated to understand what physiology and biochemical strategy these plants used to sitto the environment of sand burial and keep growth. The result showed:1. Sand burial changed the plant microhabitat. Because seaside sand and Horqin sandy landbelong to different climatic zones, the average soil organic carbon content of seaside sandslightly was lower, total nitrogen, soil salt content is higher. After Sand burial, soil moistureand temperature of two sand areas showed similar trends. As the thickness of sand burialincreases, soil water content of the coastal sandy increased from0.3%to8.7%; soil watercontent of Horqin sandy land increased from0.11%to5.5%. With increasing burial depth,soil temperature of coastal sandy dropped from41°C to20°C; soil temperature of Horqinsandy land dropped from47°C to23°C.2. In the case of sand burial, the growth strategy of two sandy desert plants are different.Messerschmidia sibirica Linn of coastal sand, is a herbaceous perennial rhizome, accelerated growth of the upper part in the mild and moderate burial., the leaves of its wholeplant turned yellow, but the top of the shoot apex became coarsening and abnormal growth,and the branches of axillary bud rapidly grow the top of the sand surface to maintain the plantsurvival, it's a resistance plant to sand burial.Vitex trifolia var.simplicifolia of coastal sand, which is a semi-shrubs, the main stem iscreeping and rooting section. In mild and moderate sand burial, stolon growth acceleration(Compared with the control, the growth length of stem is1.5to4folds higher.), sand burialsites grow adventitious roots, leaf photosynthesis' enhancement in the sand. However, severesand buried inhibits the growth of at the top stolons and adventitious roots. When full plantwas covered with sand, the strategy of plant adapting to sand burial was that leaves undersand died and the material in the leaves were transferred to the apex of creeping stem, butlonger full sand burial will cause plant to die.Artemisia ha lodendron in Horqin Sand Land is semi-shrub, thick taproot. Planted in mildand moderate sand, the yellow leaves under the sand fall off. Not the san-buried, the top of thegrowing get rid of sand buried by fast-growing, it is a resistance plant to sand buried.Lespedeza bicolor Turcz in the mild and moderate sand, planted in a short time (6days), theleaves of Lespedeza bicolor Turcz turned yellow and fall off. With the extension of sandburied time, the leaves of Lespedeza bicolor Turcz wilt, some leaves off, it is a kind of plantresistance to sand burial.3.Although there are some differences in physicochemical property, there are somesimilarities on the ability that the physiological regulation of generality of plants(1) plant leaf cell membrane permeability, MDA content and RWC affected by SandBurialIn the5th day, the plant leaf cell membrane permeability and MDA content ofMesserschmidia sibirica Linn were decreased by different thickness of sand burial. in thesevere sand burying declined by38%, while the same plant sand plant leaf cell membranepermeability, MDA, RWC were higher than that of sand under the blade more sand under low;Vitex trifolia var.simplicifolia were buried in mild and moderate sand about5days, wholeplant cell membrane permeability in adult and juvenile growth of leaves increased, and MDAincreased too, but the same sand leaf cell membrane permeability, MDA levels were higher inthe sand; Lespedeza bicolor Turcz buried in sand6days, with sand burial depth increased, the plant sand on MDA content in leaves were higher than that of the control. Research showsthat, after processing the whole plant leaves buried in sand and sand on the leaf cellmembrane permeability and membrane lipid peroxidation product is positive correlation,negative correlation with the leaf water content. Sand burial stress caused by blade cells inintimal lipid peroxidation increased membrane leading to impaired physiological reason.While the sand burial make sand plant leaf close to the sand surface and withstand droughtand ground thermal radiation stress is induced by cell membrane lipid peroxidation and cellmembrane permeability increase aggravating ecological factor. At the same time sand burialalso make leaves encounter dark, hypoxia induced cell membrane lipid peroxidation. AndVitex trifolia var.simplicifolia differs from the sand plant, in the sand buried6days, the samecell membrane permeability in leaves, MDA content is lower than the sand, on the one handand the special filamentous lobes on the sand environment change insensitive about,on theother hand the dark, hypoxia and CO2deficiency under the sand induced cellular respirationmetabolic disturbances induced oxygen free radical accumulation and membrane lipidperoxidation in exacerbation may be the cause of sand under the leaf cell membranepermeability and MDA content is more than the sand of reason.(2) Sand burial affects the activity of antioxidant enzymes in plant leavesIn the5th day, the activity of SOD, CAT of whole plant leaf of Messerschmidia sibiricaLinn increased, on the same plant, SOD and CAT activity in the leaf above the sand werehigher than that buried under the sand, in which mild sand burial and moderate buried sandleaf CAT activity respectively12%and24%higher than that under the sand; Vitex trifoliavar.simplicifolia after buried in sand5Days, POD and SOD activity in the adult and juvenileleaves increases with sand bury gradient changing, the POD and SOD activity of leaves werehigher than the buried; With the conditions buried under the sand, whole plant leaf POD andCAT activity of Artemisia ha lodendron increased, meanwhile the activity of POD and CAT ofleaves is higher than that of the buried; only the activity of CAT in Lespedeza bicolor isrising.Research showed that sand burial stress induced intracellular oxygen free radicalsproduced activation of the antioxidant system, make the sand plant anti-oxidative enzymeactivity increased, but a variety of plant response to sand burial stress needed for antioxidantenzymes of different types, the plant species adapt to adverse environment is related todifferent physiological mechanism. (3)The influence of plant leaves to osmotial content by sand buriedThe three kinds of plants (Messerschmidia sibirica Linn,Artemisia ha lodendron andVitex trifolia var.simplicifolian)are increasing the proline content of whole leaves with theincrease in the thickness of sand burial, especially Artemisia halodendron. The whole plantdeal with by Sand burial average proline content increased1.4times,1.2times and2.9times(P <0.05) respectively compared with the control. At the same time the proline content ofleaves on the sand was lower than the under sand leaves, but leaf soluble sugar and prolineresponses to sand burial contrary, decreased as the sand buried depth increased. The solubesugar content of Messerschmidia sibiricasoluble content decreased more, decline of60%,63%and80%respectively. Research showed that the accumulation of proline can improvethe osmotic adjustment capacity of plant leaf cells and maintain the integrity of the cellmembrane structure. However, if proline accumulation was excessive, it can damage the plantcell, such as the accumulation of proline in Lespedeza bicolor TurczTo sum up, plants under sand buried stress can improve the vitality of the antioxidantenzymes, gets rid of active oxygen radicals in vivo, protect cell membranes from harm.Meanwhile, the rapid accumulation of osmolytes, can reduce the water potential of the cells,to ensure that cells absorb moisture from the surrounding normally, plays an important role toresist damage caused by sand burial and maintain the normal physiological metabolism forplants. Thus plants can continue to growth normally..