| Natural vegetation rehabilitation is an essential way and the main measure to control soiland water loss and improve ecological environment in the hilly-gullied Loess Plateau.In-depth study on the effects of soil erosion environment on physiological activities of naturalvegetation and the physiological mechanisms and adaptive capacities of different plants is ofgreat significance for selecting erosion-resistant plants available to vegetation rehabilitation inthis region. Furthermore, antioxidant properties and osmotic adjustments are importantphysiological characteristics reflecting the resistances of plants. Thus, the objective of thisstudy was to explore antioxidative and osmoregulatory mechanisms and correspondinglyrestricting factors of native plants and their adaptive capacities on different sites of hilly-gullysystems in the Yanhe watershed of this region. And this study was based on defining thecharacteristics of soil erosion environment and the relative effect of genetic background andsoil erosion environment on antioxidant properties and osmotic adjustments. Throughsampling of plant leaves of thirty-eight species of thirty-two genera in eighteen families,activities of three antioxidases (superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT)), contents of two non-enzymatic antioxidants (reduced glutathione (GSH) andcarotenoid (Car)), and contents of malondialdehyde (MDA) and six osmotic adjustmentsubstances (Na+, K+, Cl-, proline, soluble protein and soluble sugar) were determined. Andenvironmental data of sampling sites were accessed. The main results are shown as follows:1. In the study region, soil erosion intensities on shady gully lands, shady intergully landsand sunny intergully lands were mediate or strong and those on sunny gully lands werestronger or severe while on hilltops were lighter. The soil possessed features of appropriatetightness, alkalescence and water and nutrient deficiency. Hydrothermal condition, soilvolume weight, altitude, soil organic matter and soil water were selected as typical soilerosion environmental factors which represented climate condition, soil tightness, terrain, soilnutrient and water condition, respectively.2. The antioxidative mechanisms and capacities of test plants depended on geneticbackground largely, while soil erosion environment determined their adaptation and evolutiondirection. Antioxidase-dominated mechanisms were adopted by plants of Gramineae and Leguminous. Their main antioxidases were greatly subjected to soil erosion environment, butthey had strong antioxidant capacities. GSH-dominated mechanism was adopted by plants ofRhamnaceae and Thymelaeaceae while antioxidases and non-enzymatic antioxidants werejointly adopted by plants of other families. For plants of Rhamnaceae, Thymelaeaceae,Aceraceae, Fagaceae, Rosaceae, Caprifoliaceae, Cyperaceae, Elaeagnaceae, Oleaceae,Betulaceae, Labiatae and Asclepiadaceae, their inhibitions of main antioxidants on membranelipid peroxidations were not strong and plants of Oleaceae and Rosa xanthina of Rosaceaewere subjected to soil nutrients while plants of Cyperaceae were weakly subjected. For plantsof Compositae and Loganiaceae, their inhibitions of main antioxidants on membrane lipidperoxidations were strong, but the former was greatly subjected to soil erosion environment.For plants of Valerianaceae and Cupressaceae, antioxidases and non-enzymatic antioxidantswere all low in activities and contents, and the former was subjected to both terrain and soilconditions. For different species of Gramineae, Leguminosae, Compositae and Rosaceae,there were certain differences in antioxidative mechanisms and restricting environmentalfactors.3. The overall trend in antioxidant capacities of test plants was as follows: for differentfamilies, Gramineae and Leguminosae＞Aceraceae and Fagaceae＞Asclepiadaceae,Compositae, Betulaceae, Oleaceae, Rosaceae, Elaeagnaceae, Cyperaceae, Rhamnaceae,Caprifoliaceae, Loganiaceae, Labiatae, Thymelaeaceae, Valerianaceae and Cupressaceae; forthe species of Gramineae, Stipa bungeana and Cleistogenes chinensis＞Cleistogenessquarrosa, Leymus secalinus, Bothriochloa ischaemum and Stipa grandis＞Phragmitesaustralis; for the species of Leguminosae, Astragalus scaberrimus, Astragalus melilotoidesand Lespedeza davurica＞Glycyrrhiza uralensis and Sophora davidii; for the species ofCompositae, Heteropappus altaicus＞Dendranthema indicum and Artemisia leucophylla＞Artemisia gmelinii, Artemisia scoparia and Artemisia frigid; and for the species of Rosaceae,Rosa xanthina＞Cotoneaster multiflorus, Pyrus betulifolia, Potentilla tanacetifolia andSpiraea salicifolia.4. The osmoregulatory mechanisms and functions of test plants also depended on geneticbackground largely. Drought resulted in the accumulations of osmotic adjustment substancesdirectly while terrain, soil tightness and nutrient condition interfered or assisted osmoticadjustments mediately. Inorganic ions and organic solutes were joinly adopted by plants ofElaeagnaceae, Compositae, Loganiaceae and Thymelaeaceae to maintain their turgorpressures. Thereinto, plants of Compositae was greatly subjected to soil erosion environment,but they had strong osmoregulatory functions; there was significantly coordinated variationbetween contents of Na+and K+of plants of Thymelaeaceae, but for plants of Elaeagnaceae and Loganiaceae, their main osmotic adjustment substances exerted non-synergistic effectsand negatively synergistic effects, respectively. By contrast, plants of other families adoptedinorganic ions involved in their osomtic adjustments, thus their osmoregulatory functionswere not strong. Thereinto, plants of Rosaceae, Gramineae, Valerianaceae and Oleaceae wereweakly subjected to soil erosion environment. There were obvious differences inosmoregulatory mechanisms and restricting environmental factors among different species ofCompositae while unconspicuous among different species of Rosaceae, Leguminosae andGramineae.5. The overall trend in osmoregulatory function of test plants was as follows: fordifferent families, Elaeagnaceae, Compositae, Loganiaceae and Thymelaeaceae＞Asclepiadaceae, Aceraceae, Rosaceae, Caprifoliaceae, Rhamnaceae, Labiatae, Betulaceae,Valerianaceae, Fagaceae, Oleaceae, Leguminosae, Cyperaceae, Gramineae and Cupressaceae;for the species of Compositae, Artemisia leucophylla, Artemisia scoparia, Dendranthemaindicum and Heteropappus altaicus＞Artemisia gmelinii and Artemisia frigid; for the speciesof Rosaceae, Potentilla tanacetifolia and Rosa xanthina＞Spiraea salicifolia, Pyrusbetulifolia and Cotoneaster multiflorus; for the species of Leguminosae, Glycyrrhiza uralensis＞Sophora davidii, Astragalus melilotoides, Lespedeza davurica and Astragalusscaberrimus; and for the species of Gramineae, Leymus secalinus, Bothriochloa ischaemumand Phragmites australis＞Cleistogenes chinensis, Stipa bungeana, Cleistogenes squarrosaand Stipa grandis.6. Based on the above two physiological characteristics, the overall trend in test plants’adaptations to the soil erosion environment was as follows: for different families, Gramineae,Leguminosae and Aceraceae＞Compositae, Loganiaceae and Elaeagnaceae＞Rosaceae,Asclepiadaceae, Betulaceae, Caprifoliaceae, Cyperaceae, Oleaceae and Valerianaceae; for thespecies of Gramineae, Stipa bungeana, Cleistogenes chinensis, Leymus secalinus,Cleistogenes squarrosa and Bothriochloa ischaemum＞Stipa grandis and Phragmitesaustralis; for the species of Leguminosae, Astragalus scaberrimus, Astragalus melilotoidesand Lespedeza davurica＞Glycyrrhiza uralensis and Sophora davidii; for the species ofCompositae, Artemisia leucophylla, Dendranthema indicum, Heteropappus altaicus andArtemisia scoparia＞Artemisia gmelinii and Artemisia frigid; and for the species ofRosaceae, Rosa xanthina, Potentilla tanacetifolia and Cotoneaster multiflorus＞Pyrusbetulifolia and Spiraea salicifolia.7. The activities of SOD and contents of MDA, Na+, proline, solute protein and solutesugar of test plants, which were all sensitive to soil erosion environment, could bephysiological indexes used to select erosion-resistant plants. |
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