The root habits of desert plants /

Photocopy. Ann Arbor, Mich. : University Microfilms International, 1980.

腾格里沙漠沙坡头地区几种植物水分生理生态特性的比较研究

本研究是中日合作项目“中国沙漠化机制及其控制”下的子项目“人工环境下植物抗逆性及其生理生态特性研究”的一个重要部分。研究工作选取腾格里沙漠东南缘的沙坡头地区作为研究地点和种子采集地，选择分布于不同类型沙丘的一年生草本作为供试植物。 通过对两种沙生植物沙米(Aqriophyllum squarrosum)和雾冰藜（Bassia dasyphylla)水分生理生态特性的比较研究，野外调查与控制环境下的生理生态学研究相结合，探讨了它们对不同水分生境的适应性。 结果表明，水分胁迫下沙米（流动沙丘先锋种）与雾冰藜（半固定和固定沙丘伴生种）表现出不同的生理生态特性，即沙米对水分胁迫比雾冰藜更为敏感，表现出不耐旱的水分生理生态特性;而雾冰藜则表现出旱生植物的水分生理生态特性。联系其分布生境水分条件可知，沙米和雾冰藜水分生理生态特性的差异是导致二者分布生境不同的主要原因之一。 本研究同时也从气孔功能的角度探讨了水分胁迫下植物蒸腾和光合速率下降的可能原因，并就本实验结果讨论了流动沙丘先锋植物沙米的生态类型划分及其对流动沙丘沙埋逆境的适应性。

中国西北地区分布的几种荒漠植物的生理生态学特性研究

白沙蒿(Artemisia sphaerocephala Krasch.)是中国西北部沙漠的流动及固定沙丘上广泛分布的优势种灌木。瘦果小而轻;借助显微镜和扫描电镜对瘦果的形态结构进行了观察，其种子的种皮与果皮愈合，果皮外层为很厚的粘液层，其粘液层在遇湿后迅速吸水膨胀，其重量增至原来的589倍。在自然生境中，粘液物质将沙粒粘附于瘦果的周围，使瘦果的重量发生变化。瘦果能长时间在水上漂浮，粘液物质有助于种子的萌发和苗的发育。白沙蒿产生三种不同颜色的瘦果，其种子具有不同的萌发速率但最终达到相同的萌发率。瘦果的粘液物质对白沙蒿种子的传播与萌发具有重要的生态意义。白沙蒿种子为需光种子，种子在光下萌发而在暗中受到抑制。种子萌发的适宜温度为250 C，在100 C和300 C萌发速率和萌发率都很低，萌发在50 C受到抑制。种子在沙中被埋越深，其萌发速率和萌发率就越低。在沙平面下2厘米或更深层沙土下出苗率为零。但是，当将种子上层沙土移走，只保留0.5厘米沙土覆盖种子，这些种子的萌发率达到原先就位于沙土下0.5厘米的种子的萌发率，但是后者的萌发速率较高。土壤水分含量越高，从1. 7%到14. 7%，其萌发就越快。土壤水分含量从19.4%起，种子的萌发受到了延迟，苗的发育受到了抑制。 梭梭(Haloxylon ammodendron)是我国西北荒漠中分布的多年生植物，属中亚荒漠植被成分。其种子萌发的最适温度为loo C，亚适宜温度为15-20 0C。从200C起，温度越高，萌发比率越低。种子无论在光下和暗中都能萌发，萌发率无显著性差异。浓度低于0.2 molL的NaCl溶液对萌发的影响不大;但从0.8 mol/L起，萌发率随着浓度增高而降低，直至为零。将在盐溶液中处理9d的种子转移至蒸馏水后，原来较高浓度下的种子具有较高的萌发恢复率。不同浓度下的种子的萌发率和萌发恢复率要比蒸馏水中的低，表明NaCl处理后的部分种子永久地失去萌发力。梭梭的种子为短命种子，在自然状态下，种子的含水量为8.5%，寿命约为10个月。将梭梭种子含水量降至2. 5%和1.4%，其耐贮藏力增强。经过500 C下5天和10天的人工加速老化后，超干种子表现出较强的抗老化能力。与对照相比，超干种子萌发率、根长及活力指数等均显著提高。较低的电导率和较高的脱氢酶活性，说明种子在超干处理后表现出了膜系统的完整性和较高的种子生活力。超干处理既能显著提高梭梭种子的耐贮性，也能有效保持种质的稳定性，是梭梭种质资源保护的重要途径之一。 沙柳（Salix psammophila）是毛乌素沙地流动沙丘和固定沙丘上广泛分布的重要固沙植物。沙柳叶片的光合速率呈现出双峰型的日动态变化，在午后14点出现光合午休现象。蒸腾速率呈现出单峰型的日动态变化，蒸腾在午后15点达到最大。水分利用效率在早晨9点后保持在2.5 μmol C02．mmol-l H20左右。叶片水分亏缺也表现出规律性的变化。从早晨开始，叶片水分亏缺逐渐增强，在18时达到最大值。比较生长季节的不同时期环境因子的变化情况表明，春末的光照强度和气温比夏末高，但土壤水分含量则相反。沙柳在春末的光合速率、蒸腾速率分别是夏末的79%和72.4%，表明水分亏缺是影响沙柳生长发育的主要限制因素。

Bioprospecção de fungos endofílicos Camarops sp., Periconia atropurpurea e Pseudofusicoccum stromaticum e avaliação epigenética de Phoma sp

Pós-graduação em Química - IQ

In vitro efficacy of selected medicinal plants from Cholistan desert, Pakistan, against gastrointestinal helminths of sheep and goats

Gastrointestinal helminths are a major constraint to small ruminants in extensive husbandry systems of tropical regions. Yet, unavailability, high prices, side effects, and development of parasite resistance often limit the use of synthetic anthelmintics. Traditional medicinal plants might be an effective low-cost alternative. Therefore the in vitro anthelmintic activity of leaf extracts of the ligneous plants Capparis decidua, Salsola foetida, Suaeda fruticosa, Haloxylon salicornicum, and Haloxylon recurvum from Cholistan, Pakistan, was investigated against adult worms of Haemonchus contortus, Trichuris ovis, and Paramphistomum cervi. Various concentrations (from 7.8 to 500 mg dry matter ml^(−1)) of three extracts (aqueous, methanol, and aqueous-methanol) of each plant were tested at different time intervals for their anthelmintic activity via adult motility assay. Plant species (p<=0.01), extract type (p<=0.001), parasite species (p<=0.001), extract concentration (p<=0.001), time of exposure (p<=0.001) and their interactions (p<=0.001) affected the number of immobile or dead helminths. The 50% lethal concentration (LC_(50)) values indicated that the methanol and aqueous-methanol extracts of C. decidua, H. recurvum, and H. salicornicum as well as the methanol extract of S. fruticosa have the potential to be developed into plant-based remedies against the studied helminths. Further studies are needed to investigate the in vivo anthelmintic activity of these extracts, in order to develop effective, cheap and locally available anthelmintics for pastoralists in Cholistan and neighbouring desert regions.

Feasibility of cyanobacterial inoculation for biological soil crusts formation in desert area

Practical testing of the feasibility of cyanobacterial inoculation to speed up the recovery of biological soil crusts in the field was conducted in this experiment. Results showed that cyanobacterial and algal cover climbed up to 48.5% and a total of 14 cyanobacterial and algal species were identified at the termination of inoculation experiment; biological crusts' thickness, compressive and chlorophyll a content increased with inoculation time among 3 years; moss species appeared in the second year; cyanobacterial inoculation increased organic carbon and total nitrogen of the soil; total salt, calcium carbonate and electrical conductivity in the soil also increased after inoculation. Diverse vascular plant communities composed of 10 and 9 species are established by cyanobacterial inoculation on the windward and leeward surface of the dunes, respectively, after 3 years. The Simpson index for the above two communities are 0.842 and 0.852, while the Shannon-Weiner index are 2.097 and 2.053, respectively. In conclusion, we suggest that cyanobacterial inoculation would be a suitable and effective technique to recover biological soil crusts, and may further restore the ecological system. (C) 2008 Published by Elsevier Ltd.

Investigating the removal of some pharmaceutical compounds in hospital wastewater treatment plants operating in Saudi Arabia

The concentrations of 12 pharmaceutical compounds (atenolol, erythromycin, cyclophosphamide, paracetamol, bezafibrate, carbamazepine, ciprofloxacin, caffeine, clarithromycin, lidocaine, sulfamethoxazole and Nacetylsulfamethoxazol (NACS)) were investigated in the influents and effluents of two hospital wastewater treatment plants (HWWTPs) in Saudi Arabia. The majority of the target analytes were detected in the influent samples apart from bezafibrate, cyclophosphamide, and erythromycin. Caffeine and paracetamol were detected in the influent at particularly high concentrations up to 75 and 12 ug/L, respectively. High removal efficiencies of the pharmaceutical compounds were observed in both HWWTPs, with greater than 90 % removal on average. Paracetamol, sulfamethoxazole, NACS, ciprofloxacin, and caffeine were eliminated by between >95 and >99 % on average. Atenolol, carbamazepine, and clarithromycin were eliminated by >86 % on average. Of particular interest were the high removal efficiencies of carbamazepine and antibiotics that were achieved by the HWWTPs; these compounds have been reported to be relatively recalcitrant to biological treatment and are generally only partially removed. Elevated temperatures and high levels of sunlight were considered to be the main factors that enhanced the removal of these compounds.

Vegetation changes in a river oasis on the southern rim of the Taklamakan Desert in China between 1956 and 2000

The indigenous vegetation surrounding the river oases on the southern rim of the Taklamakan Desert has drastically diminished due to overexploitation as a source of fodder, timber and fuel for the human population. The change in the spatial extent of landscape forms and vegetation types around the Qira oasis was analyzed by comparing SPOT satellite images from 1998 with aerial photographs from 1956. The analysis was supplemented by field surveys in 1999 and 2000. The study is part of a joint Chinese-European project with the aim of assessing the current state of the foreland vegetation, of gathering information on the regeneration potential and of suggesting procedures for a sustainable management. With 33 mm of annual precipitation, plants can only grow if they have access to groundwater, lakes or rivers. Most of the available water comes into the desert via rivers in the form of seasonal flooding events resulting from snow melt in the Kun Lun Mountains. This water is captured in canal systems and used for irrigation of arable fields. Among the eight herbaceous and woody vegetation types and the type of open sand without any plant life that were mapped in 2000 in the oasis foreland, only the latter, the oasis border between cultivated land and open Populus euphratica forests and Tamarix ramosissima-Phragmites australis riverbed vegetation could be clearly identified on the photographs from 1956. The comparison of the images revealed that the oasis increased in area between 1956 and 2000. Shifting sand was successfully combated near to the oasis borders but increased in extent at the outward border of the foreland vegetation. In contrast to expectations, the area covered with Populus trees was smaller in 1956 than today due to some new forests in the north of the oasis that have grown up since 1977. Subfossil wood and leaf remnants of Populus euphratica that were found in many places in the foreland must have originated from forests destroyed before 1956. In the last 50 years, the main Qira River has shifted its bed significantly northward and developed a new furcation with a large new bed in 1986. The natural river dynamics are not only an important factor in forming the oasis’ landscape but also in providing the only possible regeneration sites for all occurring plant species. The conclusion of the study is that the oasis landscape has changed considerably in the last 50 years due to natural floodings and to vegetation degradation by human overexploitation. The trend towards decreasing width of the indigenous vegetation belt resulting from the advancing desert and the expansion of arable land is particularly alarming because a decrease in its protective function against shifting sand can be expected in the future.

Flower and seed biomass, and germination rate of arctic tundra plants in response to long term experimental warming

We provide new information on changes in tundra plant sexual reproduction in response to long-term (12 years) experimental warming in the High Arctic. Open-top chambers (OTCs) were used to increase growing season temperatures by 1-2 °C across a range of vascular plant communities. The warming enhanced reproductive effort and success in most species; shrubs and graminoids appeared to be more responsive than forbs. We found that the measured effects of warming on sexual reproduction were more consistently positive and to a greater degree in polar oasis compared with polar semidesert vascular plant communities. Our findings support predictions that long-term warming in the High Arctic will likely enhance sexual reproduction in tundra plants, which could lead to an increase in plant cover. Greater abundance of vegetation has implications for primary consumers - via increased forage availability, and the global carbon budget - as a function of changes in permafrost and vegetation acting as a carbon sink. Enhanced sexual reproduction in Arctic vascular plants may lead to increased genetic variability of offspring, and consequently improved chances of survival in a changing environment. Our findings also indicate that with future warming, polar oases may play an important role as a seed source to the surrounding polar desert landscape.

Dry cooling with night cool storage to enhance solar power plants performance in extreme conditions areas

Solar thermal power plants are usually installed in locations with high yearly average solar radiation, often deserts. In such conditions, cooling water required for thermodynamic cycles is rarely available. Moreover, when solar radiation is high, ambient temperature is very high as well; this leads to excessive condensation temperature, especially when air-condensers are used, and decreases the plant efficiency. However, temperature variation in deserts is often very high, which drives to relatively low temperatures during the night. This fact can be exploited with the use of a closed cooling system, so that the coolant (water) is chilled during the night and store. Chilled water is then used during peak temperature hours to cool the condenser (dry cooling), thus enhancing power output and efficiency. The present work analyzes the performance improvement achieved by night thermal cool storage, compared to its equivalent air cooled power plant. Dry cooling is proved to be energy-effective for moderately high day–night temperature differences (20 °C), often found in desert locations. The storage volume requirement for different power plant efficiencies has also been studied, resulting on an asymptotic tendency.

Ornamentals for low-elevation desert areas of southern California /

Mode of access: Internet.

Error, Bias, and Long-Branch Attraction in Data for Two Chloroplast Photosystem Genes in Seed Plants

Sequences of two chloroplast photosystem genes, psaA and psbB, together comprising about 3,500 bp, were obtained for all five major groups of extant seed plants and several outgroups among other vascular plants. Strongly supported, but significantly conflicting, phylogenetic signals were obtained in parsimony analyses from partitions of the data into first and second codon positions versus third positions. In the former, both genes agreed on a monophyletic gymnosperms, with Gnetales closely related to certain conifers. In the latter, Gnetales are inferred to be the sister group of all other seed plants, with gymnosperms paraphyletic. None of the data supported the modern ‘‘anthophyte hypothesis,’’ which places Gnetales as the sister group of flowering plants. A series of simulation studies were undertaken to examine the error rate for parsimony inference. Three kinds of errors were examined: random error, systematic bias (both properties of finite data sets), and statistical inconsistency owing to long-branch attraction (an asymptotic property). Parsimony reconstructions were extremely biased for third-position data for psbB. Regardless of the true underlying tree, a tree in which Gnetales are sister to all other seed plants was likely to be reconstructed for these data. None of the combinations of genes or partitions permits the anthophyte tree to be reconstructed with high probability. Simulations of progressively larger data sets indicate the existence of long-branch attraction (statistical inconsistency) for third-position psbB data if either the anthophyte tree or the gymnosperm tree is correct. This is also true for the anthophyte tree using either psaA third positions or psbB first and second positions. A factor contributing to bias and inconsistency is extremely short branches at the base of the seed plant radiation, coupled with extremely high rates in Gnetales and nonseed plant outgroups. M. J. Sanderson,* M. F. Wojciechowski,*† J.-M. Hu,* T. Sher Khan,* and S. G. Brady