等渗的盐分和水分胁迫对芦荟幼苗生长和离子分布的效应

 研究了等渗透势（-0.44、-0.88 MPa）NaCl和PEG 6000处理对六叶龄芦荟(Aloe vera)幼苗叶片生长速率、干物质积累、电解质渗漏和离子吸收、分配的效应。结果表明: -0.44、-0.88 MPa NaCl和PEG处理10 d均明显抑制芦荟幼苗叶片伸长生长,植株干物质积累速率显著降低, 叶片含水量降低,叶片细胞电解质渗漏率上升。NaCl对芦荟幼苗生长的抑制作用显著大于PEG处理的。不同器官离子含量、根系和叶片横切面X-射线微区分析结果表明, NaCl胁迫导致芦荟体内Na+、Cl－含量显著上升,根中增幅明显高于叶片,其中Cl－尤为显著。NaCl胁迫严重抑制芦荟对K+ 和Ca2+ 的吸收及其向叶片的运输,根、叶K+/Na+、Ca2+/Na+ 比率显著下降,而PEG胁迫对离子平衡的干扰较轻,是芦荟对水分胁迫的适应能力高于盐胁迫的主要原因之一。但芦荟对 -0.44～-0.88 MPa NaCl胁迫仍有一定的适应能力,主要原因是：1) 根系对离子的选择性吸收和运输较强,并随着盐胁迫强度增加其选择性增强; 2) 芦荟叶片中的盐分在贮水组织中显著积累,明显高于其它组织细胞。同时,芦荟是CAM（景天酸代谢）途径植物,蒸腾极小,盐分随蒸腾流进入地上部的机会小。     

Interferences between Sphagnum and vascular plants: effects on plant community structure and peat formation

The interference between vascular plants and peat mosses with respect to nitrogen and phosphorus was studied in a fertilization experiment and with respect to competition for light in a removal experiment in poor fens with either soligenous or topogenous hydrology using Narthecium ossifragum (L.) Huds. and three species of Sphagnum sect. Sphagnum as targets. Adding fertilizer either on the moss surface or below it confirmed the hypotheses of an asymmetric competition for nutrients, viz. that the Sphagnum mosses relied on the atmospheric supply while Narthecium depended on mineralization in the peat. The results of the removal experiments and the negatively correlated growth of Narthecium and Sphagnum mosses demonstrated a symmetric competition for light. The intensity of the competition for light increased as the availability of N and P increased. The nutrient resources in the total biomass decreased with decreasing standing crop of Narthecium . Only with a considerable amount of mineral nutrients in the biomass has Narthecium the capacity to grow ahead of Sphagnum, because the asymmetric competition for N and P gives Sphagnum the capacity to reduce the performance of vascular plants. The mosses are more efficient in their use of nutrients and produce a decay-resistant litter inducing low mineralization and increasing the peat accumulation rate, and that withdraws N and P from the rhizosphere. The Sphagnum mosses thus act as ecological engineers structuring the plant community and determining the carbon balance of the system. The development of ombrotrophic conditions through peat accumulation seems less probable on soligenous than on topogenous mires owing to the higher mineralization rate there supporting the growth of the vascular plants. Correspondingly, disturbances of the Sphagnum cover, such as through airborne pollutants, increase the productivity of the vascular plants and decrease the capacity for carbon accumulation.     

Response curves and the environmental limits for peat-forming species in the northern Andes

Peatlands, with organic soils, are usually dominated by one or a few species. Above and belowground ecological processes are regulated by the characteristics of the dominant species in the peat. Understanding how these species relate to climatic or water chemistry gradients will help to predict the fate of those ecosystems under current climate change. The patterns of abundance and occurrence of 12 major peat-forming species from different structural plant groups were quantified along gradients of elevation, precipitation, and water chemistry. The species were distributed in four major structural groups: cushion plants, true mosses, sedges, and Sphagnum mosses. A response curve for each species was built with Generalized Additive Models. Niche breadths, species tolerances, and species optima were estimated using bootstrap resampling. Our results showed that species were limited in their elevational ranges; Sphagnum species were biased toward low to intermediate elevations, sedges, and true mosses to intermediate elevations and cushion plants to very high elevations. Sphagnum species were more likely to occur in sites with low precipitation, while sedges preferred wet sites. Sphagnum species preferred habitats with acidic pH. The species tolerances and optimum distributions are an indication to the vulnerability of the species to changes in their environment. Species with limited tolerances are more vulnerable, such as the narrow elevational distribution of cushion plants or the low pH and narrow tolerances observed for Sphagnum species. Climate and hydrological changes will very possibly affect the distribution of those species forcing changes on ecosystem functioning.     

离子吸收分布与几种荒漠植物适应性的关系

用压力室灌流挤压法结合原子吸收分光光度计测定了胡杨、沙枣、柽柳、梭梭和花棒等5种荒漠优势植物组织以及细胞内和质外体溶液中K+、Na+含量,并用TPS-1型光合蒸腾测定系统和露点微伏压计测定了叶片(同化枝)的蒸腾速率和组织渗透势,以分析荒漠植物离子吸收特点与其适应性的关系。结果表明:5种植物叶片(同化枝)中K+含量差异较小,但Na+含量却有极显著差异,其中梭梭Na+含量最高、胡杨和柽柳次之、花棒和沙枣相对较低,且梭梭和柽柳的根系和组织细胞膜对Na+也具有更高的透性。另外,实验结果还显示组织Na+含量与组织渗透势和蒸腾失水率均呈显著负相关,即Na+的吸收、积累可能在渗透调节和减少水分散失中具有重要作用。由此可见,梭梭和柽柳能够通过大量吸收和积累无机离子来降低渗透势、增强吸水力,同时减少蒸腾失水,具有很强的荒漠环境适应能力;而胡杨蒸腾耗水量较大、花棒和沙枣生理吸水的动力不足,与梭梭和柽柳相比,其荒漠环境适应能力相对较弱。     

Physiological and Biochemical Aspects of Halophyte Ecology

Physiological and biochemical features of euhalophytes, сrinohalophytes, and glycohalophytes growing in natural conditions in El’ton Lake area were studied. The water content in tissues, intensity of lipid peroxidation, and membrane permeability were found to determine the differentiation of plants by their salt accumulation strategy. The concentration of pigments and their ratio are related to the mesostructure of leaves and are dependent on the salt accumulation strategy and life form. The membrane complex is connected with the cell structure and photosynthetic apparatus. The specificity of ion transportation depends on the specific features of plants.     

ATPase与植物抗盐性

本文综述了高等植物细胞ATPase在盐胁迫下的活性变化及其调控机制。V型H+_ATPase与细胞离子区隔化和植物抗盐性密切相关。盐胁迫提高抗盐植物液泡膜H+_ATPase活性,主要是通过增加V型H+_ATPase主要功能亚基的基因表达以及蛋白质合成。盐胁迫通常降低质膜H+-ATPase活性,很可能是由于酶蛋白质合成受阻,质膜H+-ATPase活性的变化与盐胁迫的强度和时间长短有关。此外,本文还对ABA和Ca2+-CaM等胁迫信号物质对ATPase活性的调控及其与植物抗盐性的关系进行了总结。研究ATPase对盐胁迫的响应和调控机制,有助于阐明植物的盐生境适应机制,也有利于植物的抗盐育种工作。     

ATPase 与植物抗盐性

 本文综述了高等植物细胞ATPase在盐胁迫下的活性变化及其调控机制。V型H+_ATPase与细胞离子区隔化和植物抗盐性密切相关。盐胁迫提高抗盐植物液泡膜H+_ATPase活性, 主要是通过增加V型H+_ATPase主要功能亚基的基因表达以及蛋白质合成。盐胁迫通常降低质膜H+-ATPase活性, 很可能是由于酶蛋白质合成受阻, 质膜H+-ATPase活性的变化与盐胁迫的强度和时间长短有关。此外, 本 文还对ABA和Ca2+-CaM等胁迫信号物质对ATPase活性的调控及其与植物抗盐性的关系进行了总结。研究ATPase对盐胁迫的响应和调控机制, 有助于阐明植物的盐生境适应机制, 也有利于植物的抗盐育种工作。     

喀斯特地区植物钙含量特征与高钙适应方式分析

喀斯特地区土壤的高钙含量是影响该地区植物生理特征的最重要环境因素之一。高钙影响植物的光合作用、生长速率及磷代谢, 从而限制了许多物种在该地区的分布。选取贵州4个石漠化程度不同的地区, 测定采集地内45种优势种或常见种的地上部分和地下部分的全钙含量以及土壤的交换性钙含量。通过分析喀斯特地区植物与土壤钙含量的特征发现: 喀斯特地区植物具有较高的钙含量平均值; 土壤交换性钙含量对植物地上部分钙含量的影响总体上不显著, 对植物地下部分钙含量的影响显著; 不同类别植物的钙含量存在显著差异, 蕨类植物地上部分钙含量平均值明显低于被子植物; 不同类别植物钙的分布部位也存在显著差异, 在蕨类植物和单子叶植物中地上部分和地下部分的钙含量相近, 而双子叶植物的地上部分钙含量明显高于地下部分。分析了喀斯特地区14种优势灌木和草本植物地上部分与地下部分钙含量的差异性以及与土壤交换性钙含量的相关关系, 以此为根据将14种优势植物对土壤高钙的适应方式分为3种类型: 随遇型、高钙型和低钙型。随遇型植物的钙含量主要受土壤交换性钙含量影响, 其地上部分和地下部分的钙含量均与土壤交换性钙含量成显著正相关关系; 高钙型植物具有较强的钙富集能力, 其地上部分即使在低钙含量的土壤中也可维持较高的钙含量; 低钙型植物的地上部分即使在高钙含量的土壤中亦可维持较低的钙含量。对植物适应钙的不同方式的研究可用于筛选退化生态系统恢复所需的植物资源。     

Salt tolerance, salt accumulation, and ionic homeostasis in an epidermal bladder-cell-less mutant of the common ice plant Mesembryanthemum crystallinum

The aerial surfaces of the common or crystalline ice plant Mesembryanthemum crystallinum L., a halophytic, facultative crassulacean acid metabolism species, are covered with specialized trichome cells called epidermal bladder cells (EBCs). EBCs are thought to serve as a peripheral salinity and/or water storage organ to improve survival under high salinity or water deficit stress conditions. However, the exact contribution of EBCs to salt tolerance in the ice plant remains poorly understood. An M. crystallinum mutant lacking EBCs was isolated from plant collections mutagenized by fast neutron irradiation. Light and electron microscopy revealed that mutant plants lacked EBCs on all surfaces of leaves and stems. Dry weight gain of aerial parts of the mutant was almost half that of wild-type plants after 3 weeks of growth at 400 mM NaCl. The EBC mutant also showed reduced leaf succulence and leaf and stem water contents compared with wild-type plants. Aerial tissues of wild-type plants had approximately 1.5-fold higher Na(+) and Cl(-) content than the mutant grown under 400 mM NaCl for 2 weeks. Na(+) and Cl(-) partitioning into EBCs of wild-type plants resulted in lower concentrations of these ions in photosynthetically active leaf tissues than in leaves of the EBC-less mutant, particularly under conditions of high salt stress. Potassium, nitrate, and phosphate ion content decreased with incorporation of NaCl into tissues in both the wild type and the mutant, but the ratios of Na(+)/K(+) and Cl(-)/NO(3)(-)content were maintained only in the leaf and stem tissues of wild-type plants. The EBC mutant showed significant impairment in plant productivity under salt stress as evaluated by seed pod and seed number and average seed weight. These results clearly show that EBCs contribute to succulence by serving as a water storage reservoir and to salt tolerance by maintaining ion sequestration and homeostasis within photosynthetically active tissues of M. crystallinum.     

Occurrence of sucrose phosphatase in vascular and non-vascular plants

Green plants including representatives of angiosperms, gymnosperms, ferns, mosses, liverworts and green algae were shown to contain a specific sucrose phosphatase, the last enzyme in the pathway of sucrose synthesis. The enzyme from all species required Mg²⁺ for activity and it was partially inhibited by sucrose. It was not detected in a red alga, brown algae, or mushroom species which contain little or no sucrose.     

小陇山有毒被子植物调查

据调查统计,甘肃小陇山有毒被子植物共107种,其有毒化学成分主要为非蛋白质氨基酸、肽类、生物碱、酚类衍生物、萜类、甙类和无机及有机物等.对有毒植物的民间用毒、解毒方法进行了调查.     

Comparison of crenarchaeal consortia inhabiting the rhizosphere of diverse terrestrial plants with those in bulk soil in native environments

To explore whether the crenarchaeal consortium found in the rhizosphere is distinct from the assemblage of crenarchaeotes inhabiting bulk soil, PCR-single-stranded-conformation polymorphism (PCR-SSCP) profiles were generated for 76 plant samples collected from native environments. Divergent terrestrial plant groups including bryophytes (mosses), lycopods (club mosses), pteridophytes (ferns), gymnosperms (conifers), and angiosperms (seed plants) were collected for this study. Statistical analysis revealed significant differences between rhizosphere and bulk soil PCR-SSCP profiles (Hotelling paired T(2) test, P < 0.0001), suggesting that a distinct crenarchaeal consortium is associated with plants. In general, phylotype richness increased in the rhizosphere compared to the corresponding bulk soil, although the range of this increase was variable. Examples of a major change in rhizosphere (versus bulk soil) PCR-SSCP profiles were detected for all plant groups, suggesting that crenarchaeotes form associations with phylogenetically diverse plants in native environments. In addition, examples of minor to no detectable difference were found for all terrestrial plant groups, suggesting that crenarchaeal associations with plants are mediated by environmental conditions.     

Comparison of Crenarchaeal Consortia Inhabiting the Rhizosphere of Diverse Terrestrial Plants with Those in Bulk Soil in Native Environments

To explore whether the crenarchaeal consortium found in the rhizosphere is distinct from the assemblage of crenarchaeotes inhabiting bulk soil, PCR-single-stranded-conformation polymorphism (PCR-SSCP) profiles were generated for 76 plant samples collected from native environments. Divergent terrestrial plant groups including bryophytes (mosses), lycopods (club mosses), pteridophytes (ferns), gymnosperms (conifers), and angiosperms (seed plants) were collected for this study. Statistical analysis revealed significant differences between rhizosphere and bulk soil PCR-SSCP profiles (Hotelling paired T² test, P < 0.0001), suggesting that a distinct crenarchaeal consortium is associated with plants. In general, phylotype richness increased in the rhizosphere compared to the corresponding bulk soil, although the range of this increase was variable. Examples of a major change in rhizosphere (versus bulk soil) PCR-SSCP profiles were detected for all plant groups, suggesting that crenarchaeotes form associations with phylogenetically diverse plants in native environments. In addition, examples of minor to no detectable difference were found for all terrestrial plant groups, suggesting that crenarchaeal associations with plants are mediated by environmental conditions.     

Remodeling of chloroplast proteome under salinity affects salt tolerance of <Emphasis Type="Italic">Festuca arundinacea</Emphasis>

Acclimation of photosynthetic apparatus to variable environmental conditions is an important component of tolerance to dehydration stresses, including salinity. The present study deals with the research on alterations in chloroplast proteome of the forage grasses. Based on chlorophyll fluorescence parameters, two genotypes of a model grass species—Festuca arundinacea with distinct levels of salinity tolerance: low salt tolerant (LST) and high salt tolerant (HST), were selected. Next, two-dimensional electrophoresis and mass spectrometry were applied under both control and salt stress conditions to identify proteins accumulated differentially between these two genotypes. The physiological analysis revealed that under NaCl treatment the studied plants differed in photosystem II activity, water content, and ion accumulation. The differentially accumulated proteins included ATPase B, ATP synthase, ribulose-1,5-bisphosphate carboxylase large and small subunits, cytochrome b6-f complex iron-sulfur subunit, oxygen-evolving enhancer proteins (OEE), OEE1 and OEE2, plastidic fructose-bisphosphate aldolase (pFBA), and lipocalin. A higher level of lipocalin, potentially involved in prevention of lipid peroxidation under stress, was also observed in the HST genotype. Our physiological and proteomic results performed for the first time on the species of forage grasses clearly showed that chloroplast metabolism adjustment could be a crucial factor in developing salinity tolerance.     

Changes in chemical composition of hydrophyte leaves during adaptation to aquatic environment

Leaf chemical composition of 19 hydrophytes was studied. The content of carbon, nitrogen, nonstructural carbohydrates, organic acids, minerals, and water was determined. Hydrophytes were shown to contain less carbon (below 410 mg/g dry wt in 60% species) than terrestrial plants. Hydrophytes and terrestrial plants did not differ in the nitrogen concentration in the leaves (33 and 29 mg/g dry wt, respectively). Hydrophytes were characterized by a low content of organic acids (40–90 mg/g dry wt in 60% species) and high content of mineral compounds (90–170 mg/g dry wt in 50% species). Total amount of nonstructural carbohydrates was similar in the leaves of hydrophytes and terrestrial plants (from 120 to 190 mg/g dry wt), but the proportions of various carbohydrate fractions differed substantially. In the hydrophyte leaves, the content of soluble carbohydrates was 2.4-fold lower, whereas the content of nonstructural polysaccharides 1.2-fold higher than in terrestrial plant leaves. Two groups of correlations between parameters of leaf chemical composition were distinguished: the contents of carbon, nitrogen, and soluble sugars were positively correlated, and the negative correlation was observed between these parameters and the amounts of mineral compounds, organic acids, water, and nonstructural polysaccharides. We concluded that hydrophyte leaf chemical composition reflects a specificity of plant adaptation to aquatic environment.     

The Specific Mineral Metabolism of Selected Plant Species and its Ecological Implications

In order to assess and compare the species-specific mineral metabolism of various plants, we raised eight selected species from different families under identical nutritional conditions. Five different nutrient solutions with varying Ca/K ratios were used. After two months of growth, the leaves were harvested, arranged according to age, and analyzed with respect to their K, Ca, and Mg contents. The ion ratios, the changes of ion contents with increasing age, the differences in water- and acid-soluble Ca (calcium oxalate), and the dependence of ion uptake on variations of ion concentrations in the solutions revealed a species-specific (“physiotypic”) feature of mineral metabolism. These features are discussed taking into consideration the ecological demands of the investigated species, and assuming that the physiological peculiarities of a species should affect its ecological behavior.     

Determination of Prenylquinones in Green Photosynthetically Active Moss and Liver Moss Tissues

The prenylquinone composition of two species of mosses (Polytrichum formosum Hedw., Sphagnum acutifolium Ehrh.) and two species of liver mosses (Lunularia cruciata (L.) Dum., Pellia epiphylla (L.) Cord.) was determined and compared with the chlorophyll content and the photosynthetic activity of the intact moss and liver moss tissues.

• 1 Green moss and liver moss tissues possess in principle the same prenylquinone composition as higher plants with plastoquinone-9, α-tocopherol, α-tocoquinone and the phylloquinone K₁ as main components. On a chlorophyll basis the lipoquinone levels are lower than in higher plants. Differences among the individual mosses as well as within one species only occur in the quantitative levels of the chloroplast prenylquinones, but there are no differences between musci and liver mosses.
• 2 There are differences in the maximal fluorescence of liver mosses and mosses. The variable fluorescence in turn, which is a measure of in vivo photosynthetic activity, is very similar for all examined species of mosses and liver mosses (values from 0.7 to 1.0) but somewhat lower than in leaf pieces of higher plants. DCMU blocks the variable fluorescence and the concomitant oxygen evolution in all mosses and liver mosses.
• 3 From the lower prenylquinone levels and the low values for the variable fluorescence it is concluded that mosses and liver mosses exhibit on a chlorophyll basis fewer reaction centres and electron transport chains than chloroplasts of higher plants.

     

The Impact of Sheep Grazing on Net Nitrogen Mineralization Rate in Two Temperate Salt Marshes

Abstract: Nitrogen mineralization rate was studied in grazing trials with three different stocking rates (0, 3, 10 sheep ha^-1) in two man-made salt marshes, viz. a Puccinellia maritima -dominated low salt marsh and a high salt marsh dominated by Festuca rubra. Mineralization rates were derived from the amounts of mineral N which accumulated in situ during six-week incubation periods in tubes containing undisturbed soil cores from the upper 10 cm soil layer. The annual rates of net N mineralization were significantly higher in the better drained, high salt marsh (71 - 81 kg ha^-1 yr^-1) than in the low salt marsh (39 - 49 kg ha^-1 yr^-1). High amounts of belowground litter accumulated in the low salt marsh due to frequent water logging. Both N mineralization and nitrification rate were negatively correlated with soil water content. In the Puccinellia maritima salt marsh, grazing had neither an effect on N mineralization rates during any of the incubation periods nor on annual mineralization rates. In the Festuca rubra salt marsh, N mineralization rates increased earlier during spring at the intensively grazed site than at the moderately grazed and the ungrazed site. N mineralization and nitrification rates were significantly higher at the ungrazed site than at the intensively grazed site during the period of peak net N mineralization from the end of April until mid-June. Although sheep grazing affected the seasonal pattern of N mineralization in the high marsh, grazing did not affect the annual rate of net N mineralization.