Functional rather than structural connectivity explains grassland plant diversity patterns following landscape scale habitat loss     

Kimberley  Adam  Hooftman  Danny  Bullock  James M.  Honnay  Olivier  Krickl  Patricia  Lindgren  Jessica  Plue  Jan  Poschlod  Peter  Traveset  Anna  Cousins  Sara A. O. 《Landscape Ecology》2021,36(1):265-280

Context

Functional connectivity is vital for plant species dispersal, but little is known about how habitat loss and the presence of green infrastructure interact to affect both functional and structural connectivity, and the impacts of each on species groups.

Objectives

We investigate how changes in the spatial configuration of species-rich grasslands and related green infrastructure such as road verges, hedgerows and forest borders in three European countries have influenced landscape connectivity, and the effects on grassland plant biodiversity.

Methods

We mapped past and present land use for 36 landscapes in Belgium, Germany and Sweden, to estimate connectivity based on simple habitat spatial configuration (structural connectivity) and accounting for effective dispersal and establishment (functional connectivity) around focal grasslands. We used the resulting measures of landscape change to interpret patterns in plant communities.

Results

Increased presence of landscape connecting elements could not compensate for large scale losses of grassland area resulting in substantial declines in structural and functional connectivity. Generalist species were negatively affected by connectivity, and responded most strongly to structural connectivity, while functional connectivity determined the occurrence of grassland specialists in focal grasslands. Restored patches had more generalist species, and a lower density of grassland specialist species than ancient patches.

Conclusions

Protecting both species rich grasslands and dispersal pathways within landscapes is essential for maintaining grassland biodiversity. Our results show that increases in green infrastructure have not been sufficient to offset loss of semi-natural habitat, and that landscape links must be functionally effective in order to contribute to grassland diversity.

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Identification and in vitro biological activities of hop proanthocyanidins: inhibition of nNOS activity and scavenging of reactive nitrogen species     

Stevens JF  Miranda CL  Wolthers KR  Schimerlik M  Deinzer ML  Buhler DR 《Journal of agricultural and food chemistry》2002,50(12):3435-3443

Oligomeric proanthocyanidins constitute a group of water-soluble polyphenolic tannins that are present in the female inflorescences (up to 5% dry wt) of the hop plant (Humulus lupulus). Humans are exposed to hop proanthocyanidins through consumption of beer. Proanthocyanidins from hops were characterized for their chemical structure and their in vitro biological activities. Chemically, they consist mainly of oligomeric catechins ranging from dimers to octamers, with minor amounts of catechin oligomers containing one or two gallocatechin units. The chemical structures of four procyanidin dimers (B1, B2, B3, and B4) and one trimer, epicatechin-(4beta-->8)-catechin-(4alpha-->8)-catechin (TR), were elucidated using mass spectrometry, NMR spectroscopy, and chemical degradation. When tested as a mixture, the hop oligomeric proanthocyanidins (PC) were found to be potent inhibitors of neuronal nitric oxide synthase (nNOS) activity. Among the oligomers tested, procyanidin B2 was most inhibitory against nNOS activity. Procyanidin B3, catechin, and epicatechin were noninhibitory against nNOS activity. PC and the individual oligomers were all strong inhibitors of 3-morpholinosydnonimine (SIN-1)-induced oxidation of LDL, with procyanidin B3 showing the highest antioxidant activity at 0.1 microg/mL. The catechin trimer (TR) exhibited antioxidant activity more than 1 order of magnitude greater than that of alpha-tocopherol or ascorbic acid on a molar basis.  相似文献   

Prediction of wetting front stability in dry field soils using soil and precipitation data   总被引：1，自引：0，他引：1  

Jan M. H. Hendrickx  Tzung-mow Yao 《Geoderma》1996,70(2-4):265-280

A need exists for information regarding the stability of wetting fronts in field soils because they increase the vulnerability for groundwater contamination. In this study, we develop a simple approach for the evaluation of wetting front stability in dry soils. We show that the stability of wetting fronts in the top layer of a soil depends both on the type of soil and the intensity of the precipitation. Our approach distinguishes stability criteria for wetting events that are different for a high, intermediate, and low infiltration rate. At high infiltration rates, wetting fronts are stable if the infiltration rate exceeds or equals the saturated hydraulic conductivity of the soil. The stability criterion for low infiltration rates (less than approximately 0.2 cm/h for sand soils) is based on two characteristics times[ a gravitational time and an infiltration time. The gravitational time, t_grav, indicates when gravity and capillarity each contribute equally to the process of infiltration. The infiltration time, t_infil, is the duration of the infiltration event. Experimental and literature data show that in well-sorted laboratory sands, wetting fronts are stable when t_infil < 0.002 t_grav. This expression can also be expressed as Wi < 0.002 S² with W the total amount of precipitation, i its intensity, and S the sorptivity at a slightly positive soil-water pressure. For intermediate infiltration rates, wetting fronts remain stable as long as W is smaller than the amount of water needed to wet a distribution layer near the surface. The application of the stability criteria is demonstrated with a case study from the Sevilleta dunes near Socorro, NM.  相似文献   

Antioxidant capacity manipulation in transgenic potato tuber by changes in phenolic compounds content   总被引：1，自引：0，他引：1  

Lukaszewicz M  Matysiak-Kata I  Skala J  Fecka I  Cisowski W  Szopa J 《Journal of agricultural and food chemistry》2004,52(6):1526-1533

The main goal of this study was to generate potato tubers with increased levels of flavonoids and thus modified antioxidant capacities. To accomplish this, the vector carrying multigene construct was prepared and several transgenic plants were generated, all overexpressing key biosynthesis pathway enzymes. The single-gene overexpression or simultaneous expression of genes encoding chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) resulted in a significant increase of measured phenolic acids and anthocyanins. The increase in phenolic compounds synthesis is accompanied by decreases in starch and glucose levels in transgenic plants. The flavonoids-enriched plants showed improved antioxidant capacity; however, there is a complex relationship between antioxidant capacity and flavonoids content, suggesting the great participation of other compounds in the antioxidant potential of the plants. These other compounds are not yet recognized.  相似文献   

Factors contributing to the development of aluminum resistance in the Madeiran maize germplasm     

Miguel . A. Pinheiro de Carvalho  Jan J. Slaski  Ivo Abreu  Filipe T. Ganana  Teresa M. M. dos Santos  Lurdes Freitas  Maria R. Clemente Vieira  Antonieta Nunes  Ana Domingues  Gregory J. Taylor 《植物养料与土壤学杂志》2004,167(1):93-98

Forty genotypes representing maize genetic diversity from the Island of Madeira were screened for resistance to aluminum (Al) in nutrient solution. Seeds of maize were obtained from local farmers from field plots spread around the island in a range of altitudes from 99 to 1000 m above sea level. The content of ionic aluminum and the pH of soils cultivated with maize were determined. The mean pH value of all examined soils was 4.9, while the mean ionic Al content was 0.76 cmol kg^–1. Seventy‐two hours (h) exposure to 100 and 200 μM Al followed by a 48 h recovery period of 4‐day old seedlings revealed significant differences in Al resistance in the Madeiran maize germplasm. Root survival and regrowth exceeding 80 % of the seedlings were observed in 22 and 8 of the tested genotypes screened at 100 and 200 μM Al in nutrient solution. High Al resistance among Madeiran maize genotypes appeared not to be associated with the lower pH of soil, and did not correlate with the amount of soil Al³⁺ or the altitude at the site of collection. The high level of Al resistance of the maize cultivars indicates an initial genetic trait enhanced by open pollination of maize.  相似文献   

TAXI type endoxylanase inhibitors in different cereals   总被引：2，自引：0，他引：2  

Goesaert H  Gebruers K  Brijs K  Courtin CM  Delcour JA 《Journal of agricultural and food chemistry》2003,51(13):3770-3775

An affinity-based purification procedure with the immobilized family 11 Bacillus subtilis endoxylanase XynA allowed us to obtain high yields of highly pure endoxylanase inhibitor fractions from rye, barley, and durum wheat. In contrast, no inhibitors interacting with the B. subtilis endoxylanase affinity column are present in corn, buckwheat, rice, and oats. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis and inhibitor specificity showed that the isolated inhibitors belonged to the TAXI endoxylanase inhibitor family, thus providing a view on the diversity of this cereal inhibitor family. The isolated inhibitors are basic proteins of ca. 40 kDa, occurring in two molecular forms, with pI values of ca. 8.5 (durum wheat) and ca. 9.0 (rye, barley). They are, in general, strong inhibitors of family 11 endoxylanases but not of family 10 endoxylanases. Because cereal endogenous endoxylanases belong to the latter family, this probably indicates that they do not influence cereal metabolic processes. For the first time, endoxylanase inhibitors, similar to TAXI I and TAXI II from wheat, were isolated from durum wheat and characterized. For each cereal, high-resolution cation exchange chromatography revealed the presence of multiple isoinhibitors, each of which occurs in two molecular forms. However, in durum wheat and barley, a single isoform is predominantly present.  相似文献   

Pleiotropic effect of phenolic compounds content increases in transgenic flax plant     

Lorenc-Kukuła K  Amarowicz R  Oszmiański J  Doermann P  Starzycki M  Skała J  Zuk M  Kulma A  Szopa J 《Journal of agricultural and food chemistry》2005,53(9):3685-3692

The principal goal of this paper was to generate flax (Linum usitatissimum L.) plants with increased antioxidant properties. To accomplish this a vector containing a multigene construct was prepared, and transgenic plants overexpressing essential flavonoid biosynthesis pathway enzymes were generated and analyzed. The simultaneous expression of genes encoding chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) resulted in a significant increase of flax antioxidant capacity. To investigate the determinants of higher antioxidant properties of transgenic plants, the phenolic acids and lignans compound contents were measured. In both green part and seed extracts from transgenic plants, the phenolic acids level was increased when compared to the control. The calculated correlation coefficient between phenolic acids content and antioxidant capacity (0.82 and 0.70 for green part and flaxseed, respectively) perfectly reflects their strong relationship. The increase in yield of transgenic plants and their higher resistance to Fusarium culmorum and Fusarium oxysporum when compared to the control plants was a characteristic feature. It was assessed a very high correlation (correlation coefficient = 0.9) between phenolic acids level in flaxseed extract and resistance to F. culmorum. The flowering date of transgenic plants was approximately 3 weeks earlier than that of the control plants. Interestingly, a significant increase in monounsaturated fatty acids and a slight increase in lignans content accompanied the increase in antioxidant properties of flaxseeds.  相似文献   

Improving nutritional quality of maize proteins by expressing sense and antisense zein genes   总被引：8，自引：0，他引：8  

Huang S  Adams WR  Zhou Q  Malloy KP  Voyles DA  Anthony J  Kriz AL  Luethy MH 《Journal of agricultural and food chemistry》2004,52(7):1958-1964

The predominant proteins in maize grain are a family of alcohol-soluble prolamin storage proteins called zeins. They account for >50% of total seed proteins but are deficient in several essential amino acids. As a result, the corn grain is considered to be nutritionally poor for monogastric animals with respect to key essential amino acids, most notably lysine, tryptophan, and methionine. Thus, corn mutants with reduced levels of zeins, such as opaque-2 (o2), have been demonstrated to possess grain with improved nutritional quality characteristics. The o2 mutant has a superior amino acid composition and has been used through conventional breeding to develop Quality Protein Maize (QPM) for human and animal consumption in developing countries. With the understanding of molecular genetics of zeins and progress in biotechnology, an alternative approach to zein reduction is explored here. Through the targeted reduction of the 19-kDa alpha-zeins, increased levels of lysine, tryptophan, and methionine have been engineered in grain of transgenic hybrids. Currently, the agronomic properties and nutritional values of these transgenic lines are being evaluated.  相似文献   

Conference on the study and preservation of European Orchids,Halle, East Germany, 4–5 April 1970     

Jan Cerovsky 《Biological conservation》1971

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The responses of understorey birds to forest fragmentation, logging and wildfires: An Amazonian synthesis     

J. Barlow  C.A. Peres  P.C. Stouffer  J.M. Wunderle 《Biological conservation》2006,128(2):182-192

We combine mist-net data from 24 disturbance treatments taken from seven studies on the responses of understorey Amazonian birds to selective logging, single and recurrent wildfires, and habitat fragmentation. The different disturbance treatments had distinct effects on avian guild structure, and fire disturbance and the isolation of forest patches resulted in bird communities that were most divergent from those in continuous, undisturbed forest in terms of their species composition. Although low-intensity logging treatments had the least noticeable effects, the composition of understorey birds was still markedly different from the composition in undisturbed forest. This analysis demonstrates the importance of preventing habitat fragmentation and the spread of fires in humid tropical forests, and highlights the need for more research to determine the long-term suitability of large areas of degraded forest for forest birds.  相似文献