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Tolerance Index (tolerance + index)
Selected AbstractsThe relative importance of landscape and community features in the invasion of an exotic shrub in a fragmented landscapeECOGRAPHY, Issue 2 2006Anne M. Bartuszevige Although invasive plants are recognized as a major ecological problem, little is known of the relative importance of plant community characteristics versus landscape context in determining invasibility of communities. We determined the relative importance of community and landscape features of 30 woodlots in influencing the invasion of Lonicera maackii. We sampled woodlots using the point-quarter method and calculated canopy openness and basal areas and densities of shrub, sapling and tree species, as well as woody species richness. We used aerial photos and ArcView GIS to calculate landscape parameters from the same woodlots using a buffer distance of 1500,m. We used logistic and linear regression analyses to determine the community and landscape factors that best explain L. maackii presence and density. We also tested whether woodlot invasion by L. maackii begins at woodlot edges. Presence of L. maackii was significantly explained only by distance from the nearest town (logistic regression, p=0.017); woodlots nearer town were more likely to be invaded. Among invaded woodlots, density of L. maackii was positively related to the amount of edge in the landscape (partial R2=0.592) and negatively related to total tree basal area (partial R2=0.134), number of native woody species (partial R2=0.054), and sapling shade tolerance index (partial R2=0.054). Lonicera maackii in woodlot interiors were not younger than those on the perimeters, leading us to reject the edge-first colonization model of invasion. Our findings reveal that landscape structure is of primary importance and community features of secondary importance in the invasion of L. maackii. This shrub is invading from multiple foci (towns) rather than an advancing front. Connectivity in the landscape (i.e. the number of corridors) did not promote invasion. However, edge habitat was important for invasion, probably due to increased propagule pressure. The community features associated with L. maackii invasion may be indicators of past disturbance. [source] Similar breakdown rates and benthic macroinvertebrate assemblages on native and Eucalyptus globulus leaf litter in Californian streamsFRESHWATER BIOLOGY, Issue 4 2010IGOR LA Summary 1.,Eucalyptus globulus, a tree species planted worldwide in many riparian zones, has been reported to affect benthic macroinvertebrates negatively. Although there is no consensus about the effects of Eucalyptus on aquatic macrobenthos, its removal is sometimes proposed as a means of ecological restoration. 2.,We combined the sampling of macroinvertebrates with measurement of the colonisation of leaf packs in mesh bags, to examine the effects of riparian Eucalyptus and its litter on benthic macroinvertebrates in three small streams in California, U.S.A. Each stream included one reach bordered by Eucalyptus (E-site) and a second bordered by native vegetation (N-site). 3.,The macrobenthos was sampled and two sets of litter bags were deployed at each site: one set with Eucalyptus litter (Euc-bags) and one with mixed native tree litter (Nat-bags) containing Quercus, Umbellularia, Acer and Alnus. Bags were exposed for 28, 56 and 90 days and this experiment was repeated in the autumn, winter and spring to account for effects of changing stream flow and insect phenology. 4.,Litter input (average dry mass: 950 g m,2 year,1 in E-sites versus 669 g m,2 year,1 in N-sites) was similar, although in-stream litter composition differed between E- and N-sites. Litter broke down at similar rates in Euc-bags and Nat-bags (0.0193 day,1 versus 0.0134 day,1), perhaps reflecting the refractory nature of some of the leaves of the native trees (Quercus agrifolia). 5.,Summary metrics for macroinvertebrates (taxon richness, Shannon diversity, pollution tolerance index) did not differ significantly between the E and N sites, or between Euc-bags and Nat-bags. No effect of exposure time or site was detected by ordination of the taxa sampled. However, distinct seasonal ordination clusters were observed in winter, spring and autumn, and one of the three streams formed a separate cluster. 6.,The presence of Eucalyptus was less important in explaining the taxonomic composition of the macrobenthos than either ,season' or ,stream'. Similarly, these same two factors (but not litter species) also helped explain the variation in leaf breakdown. We conclude that patches of riparian Eucalyptus and its litter have little effect on stream macrobenthos in this region. [source] Classification of protein content and technological properties of eighteen wheat varieties grown in IranINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2006Mohammad Ali Sahari Summary The best method for wheat planning and its food industrial usage is evaluation of its technological properties. Classification of protein content and some technological properties of eighteen important Iranian wheat cultivars were investigated. Statistical analysis revealed, highest protein content (11%), protein quality (SDS = 35.6 mL), hardness degree (63%), in Rooshan of Karaj (I), Zagroos of Ahvaz (K) and Marvdasht of Karaj (O) varieties, respectively. On the basis of the quality, the Zagross of Ahvaz (K), Zarrine of Aurumieh (L), Rooshan of Karaj (I), and Chamran of Ahvaz (D) varieties were recognized for their farinograph and extensograph characteristics (water absorption = 61,65%, dough development time = 2.3,5.3 min, dough stability to break down = 15,19.3 min, mixing tolerance index = 22.3,32.3 BU, valorimetry index = 55,64.3 Unit, maximum resistance to extension = 134,450 BU, dough energy = 11.3,100.3 cm2 and extensibility = 156,179 mm). The dendrogram was classified into four groups and in general, the wheat cultivar K was the most separated from the other cultivars, followed by L and I. [source] Evaluation of Common Bean for Drought Tolerance in Juana Diaz, Puerto RicoJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2009T. G. Porch Abstract Drought tolerance is an increasingly important trait in common bean (Phaseolus vulgaris L.) due to the reduction in water resources, a shift in production areas and increasing input costs. The objective of this study was to evaluate 29 genotypes for drought tolerance under drought stress (DS) and reduced stress treatments in Juana Diaz, Puerto Rico. The use of DS and reduced stress treatments facilitated the identification of drought tolerant germplasm that also had good yield potential under more optimal conditions. Based on the results of seed yield under DS and reduced stress conditions, and DS indices, including the geometric mean (GM), stress tolerance index (STI) and percent yield reduction (YR), genotypes were identified with greater yield potential under the tested environment. Based on average GM over the 2 years, the superior common bean genotypes identified were SEA 5, G 21212, A 686, SEN 21 and SER 21. These genotypes performed well in both years and under both treatment conditions and thus may serve as parents for DS improvement and genetic analysis. [source] Root Distribution of Drought-Resistant Peanut Genotypes in Response to DroughtJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2008P. Songsri Abstract The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought. This study aimed at assessing root distributions, variations in root length density (RLD) and percentage of root distribution, and the relevance of root traits for yield of drought-resistant peanut genotypes under different available soil water levels. The experiment was conducted in the dry season during the years 2003/04 and 2004/05. Eleven peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60-3 and Tifton-8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a split-plot design with four replications. Roots were sampled by a core sampler at 37, 67 and 97 days after sowing (DAS). Root length was determined by a scanner and the WINRHIZO Pro 2004a software. RLD was calculated as the ratio of root length (cm) and soil volume (cm3). Graphical illustration of root distribution was constructed by merging RLD in the first and second soil layers (0,40 cm) as upper roots and pooling RLD at the third, fourth and fifth layers (40,100 cm) as lower roots. Pod yield, biomass and harvest index (HI) were recorded at harvest. A drought tolerance index (DTI) was calculated for each parameter as the ratio of the parameter under stress treatment to that under well-watered conditions. Variations in RLD in 40 to 100 cm layer (RLD40 to 100 cm) were found under well-watered conditions, and the peanut genotypes could be readily identified as high, intermediate and low for this trait. Changes in RLD in the 40 to 100 cm soil layer were found at 2/3 AW and were more evident at 1/3 AW. ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308 and KK 60-3 were classified as drought responsive as they increased RLD in the deeper subsoil level in response to drought. In general, RLD under drought conditions was not related to biomass production. The ability to maintain the percentage of RLD (DTI for %RLD) was related to pod yield, DTI for pod yield and DTI for HI. ICGV 98300, ICGV 98303, ICGV 98305 exhibited high DTI (RLD40 to 100 cm) which may explain their high pod yield, DTI (PY) and DTI (HI). Based on these observations we classified them as drought-avoiding genotypes. [source] WHEAT BRAN (TRITICUM AESTIVUM): COMPOSITION, FUNCTIONALITY AND INCORPORATION IN UNLEAVENED BREADJOURNAL OF FOOD QUALITY, Issue 3 2002ARCHANA SHENOY H. High fiber Chapathi, an Indian unleavened bread incorporating different levels (5,15%) of wheat bran to wheat flour was prepared and evaluated for acceptability and farinograph characteristics. Whole wheat flour, wheat bran and its differently milled fractions were analyzed for chemical composition and functional properties. The water absorption capacity of bran was slightly lower than that of flour and did not increase as a function of time. The bran incorporated doughs were difficult to knead and sticky with no change in rolling properties. Farinograph characteristics revealed an increase in dough development time and a decrease in mixing tolerance index as the level of incorporation of bran increased. Wheat bran incorporated products scored lesser for the sensory quality attributes than controls. The differences were statistically significant for products prepared with 10% and 15% bran and not significant for products prepared with 5% level of bran. It can be concluded that wheat bran can be incorporated up to a level of 5% for preparation of high fiber phulkas or chapathis without affecting sensory quality. [source] Physicochemical, rheological, and organoleptic characteristics of wheat-fenugreek supplemented blendsMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 4 2003Shalini Hooda Abstract The effect of blending of fenugreek (raw, soaked, and germinated) flour (Trigonella faenum graecum) from 5 to 20% in wheat flour on the rheological and sensory evaluation of bread, biscuit, noodle, and macroni was studied. Farinograph water absorption, dough development time, mixing tolerance index, and dough stability increased significantly with increased amount of fenugreek flour. Incorporation of fenugreek flour in wheat flour increased the protein and fat contents of blends but decreased the gluten contents. Among the supplemented blends, blends containing germinated fenugreek flour had higher protein contents (13.83,16.30%) up to 20%. Overall acceptability scores of bread, biscuit, noodles, and macroni were found highly acceptable up to 15, 10, and 20% levels, respectively. [source] In vitro selection and plant regeneration of copper-tolerant plants from leaf explants of Nicotiana tabacum L. cv. ,Xanthi'PLANT BREEDING, Issue 4 2007G. R. Rout Abstract Copper tolerance of Nicotiana tabacum L. var. Xanthi in vitro was achieved through plant regeneration from leaf explants on Murashige and Skoog's (MS) medium supplemented with 0.5 mg/l BA, 0.1,0.25 mg/l IAA and 60 ,m Cu. Tolerant organogenic calli showed more vigorous growth in medium containing 60 ,m Cu than the non-tolerant calli. Standard growth parameters such as fresh and dry weight of organogenic callus, growth tolerance index (GTI), enzyme activity (peroxidase and catalase) and copper accumulation were used as indicators of copper tolerance. The activities of peroxidase and catalase as well as estimation of protein, total amino acid and chlorophyll were greater in tolerant calli than non-tolerant ones. The GTI in the 4 weeks after the beginning of treatments yielded significant differences among the tolerant and non-tolerant organogenic callus cultures. The accumulation of copper in the tolerant calli increased significantly with an increase in copper concentration in the medium. Shoot bud regeneration was achieved in both tolerant and non-tolerant organogenic calli on MS medium containing 0.5 mg/l BA and 0.1 mg/l IAA. The tolerant regenerated shoots were rooted on half-strength basal MS medium with 60 ,m Cu for selection of tolerant clones. This study may help in the selection and characterization of Cu-tolerant lines of N. tabacum cv. ,Xanthi' for building conservation strategies and also for phytoremediation programmes. [source] | |||||||||||||