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61.
Using Leaf Mass per Area as predictor of light interception and absorption in crop/weed monoculture or mixed stands 总被引:1,自引:0,他引:1
The partitioning of light absorption is difficult to assess in natural or cultivated mixed vegetation canopies. Previous research has shown that it is possible to estimate light absorption in monospecific canopies from the Leaf Mass per Area (MA), which is closely related to the prevailing light conditions experienced by the leaf during its development.The effectiveness of this approach in assessing light partitioning at individual plant level was tested on monospecific and mixed crop/weed plots. Canopy absorbed PAR (APAR) was estimated in monocultures or 1:1 mixed stands of Abutilon theophrasti Medicus and Glycine max L. (soybean) using a relationship between intercepted PAR (IPAR) and MA, calibrated at individual leaf level against incident light measurements. The accuracy of estimates was evaluated through comparison with APAR calculated from incident light measurements taken independently at various heights at whole canopy level.The use of the experimentally assessed relationship of IPAR vs. MA provided acceptable absorption estimates. The average departure of estimates from measurements, expressed as Root Mean Squared Error (RMSE), was 10.2%. By comparison, a numerically optimized version of the model that excluded the effects of experimental errors in single-leaf PAR measurements, yielded estimates with an average RMSE of 4.8%. The lower accuracy of the estimates based on the experimental IPAR-MA relationship was due to experimental error but also to a high sensitivity of the MA-based estimates to the model coefficients.MA variability in monoculture or mixed canopies was confirmed to be highly dependent on the PAR distribution, so MA is potentially suitable for use as a predictor of light absorption. However, due to the sensitivity of the model, a high experimental accuracy in IPAR-MA assessment as well as in MA and LAI distribution has to be guaranteed in order to perform reliable estimates by this method. 相似文献
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63.
Alfaro Rene I.; Humble Leland M.; Gonzalez Paola; Villaverde Raul; Allegro Gianni 《Forestry》2007,80(4):471-479
We describe the life cycle of Megaplatypus mutatus (Chapuis)(=Platypus mutatus) and the damage it causes to poplar resourcesin Argentina. This insect, native to the subtropical and tropicalareas of South America, has extended its range into temperateregions, reaching as far south as Neuquén in ArgentineanPatagonia. The damage is caused by the adult insects, whichbore large gallery systems into living poplars (Populus spp.),willows (Salix spp.) and many other broadleaf species, includingimportant fruit trees species such as apples (Malus spp.), walnuts(Juglans spp.) and avocados (Persea spp.). The galleries degradethe lumber and weaken the tree stems, which often then breakduring windstorms. A recent introduction of M. mutatus to Italydemonstrates that this insect can be transported long distancesbetween countries, and therefore presents a threat worldwide—particularlyto poplar cultivation. We review the taxonomic nomenclaturefor this pest, provide a summary of the life cycle, hosts anddamage and summarize actions taken to reduce the risk of introductionof M. mutatus to Canada. 相似文献
64.
Gianni Andreottola Luca Bonomo Giorgia De Gioannis Elisa Ferrarese Aldo Muntoni Alessandra Polettini Raffaella Pomi Sabrina Saponaro 《Journal of Soils and Sediments》2010,10(1):142-150
Purpose
The fairly high amounts of sediments dredged in coastal or internal water bodies for navigational and/or environmental purposes claims for the identification of appropriate management strategies. Dredged sediments are frequently affected by organic and inorganic contamination, so that their reuse, as an alternative to final landfill disposal, could need remediation. In this framework, a two-year joint research project was carried out to assess the feasibility of different remediation technologies for the treatment of polluted sediments. 相似文献65.
66.
The objective of the present study was to evaluate the fertility of tetraploid plants obtained from diploid mutants that produced
2n gametes via bilateral (BSP) and unilateral sexual polyploidization (USP) schemes. Controlled matings between selected plants
from BSP and USP were carried out according to a complete diallel. The level of male and female fertility of each plant was
estimated within full-sib, half-sib and non-inbred crosses. Crosses with unrelated self-fertile and male-sterile testers were
also performed. Pollen size and stainability were determined by acetocarmine staining. The number of ovules per ovary was
counted and the callose deposition within ovules examined to evaluate embryo sac fecundity. Cross-fertility was generally
much higher for USP than BSP plants (on average, 0.3 vs. 0.03 seeds per flower pollinated). Both male and female fertility
were inversely related to the inbreeding level of cross combinations. The in vitro pollen germinability was positively correlated
to male fertility of BSP plants. The level of in vivo embryo sac sterility was not correlated to female fertility in either
BSP or USP plants. Female fertility was restored in both BSP and USP groups when plants were crossed with unrelated tetraploid
testers. Male fertility also increased in USP plants but remained rather low in the BSP plants. Scaling up the ploidy level
by means of 2n gamete union resulted in tetraploid plants with low fertility. In particular, the BSP process yielded virtually
self-sterile and highly cross-sterile plants. The well documented positive effect of sexual tetraploidization on forage yield
was accompanied by worsening of fertility traits.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
67.
Composition of peptide mixtures derived from simulated gastrointestinal digestion of prolamins from different wheat varieties 总被引:1,自引:0,他引:1
Barbara Prandi Mariangela Bencivenni Andrea Faccini Tullia Tedeschi Arnaldo Dossena Rosangela Marchelli Gianni Galaverna Stefano Sforza 《Journal of Cereal Science》2012
Gliadin content of wheat is highly variable, both qualitatively and quantitatively, in function of the plant genetic and of the growing conditions. The gliadins are among the major triggers of celiac disease: peptides derived from the gastrointestinal digestion of these proteins and absorbed from the lamina propria cause the immunological reactions that damage the villous structure in affected subjects. In the present work, the peptide mixtures generated by simulated gastrointestinal digestion of the prolamin fraction extracted from different wheat varieties (Triticum turgidum subsp. durum and Triticum aestivum) were characterized by LC/MS and LC-MS/MS techniques. Peptides related to the amount of α-gliadin, as well as toxic and immunogenic peptides for celiac patients have been identified and quantified using an isotopically labeled internal standard. The quantification demonstrated strong differences among the varieties tested. Some samples, belonging to the same varieties and/or cultivation area, showed a lower α-gliadin content, and a smaller amount of toxic and immunogenic peptides. 相似文献
68.
Marcello Donatelli Gianni Bellocchi Ephrem Habyarimana Roberto Confalonieri Fabio Micale 《Computers and Electronics in Agriculture》2009,69(2):165-170
Wind is a library providing a collection of stochastic approaches to generate wind speed data on daily and hourly time steps. Daily generation refers to as mean, maximum and minimum daily wind speed. The library is made available as software component, inclusive of hypertext help file, allowing the development of language-independent clients under Windows operating systems. The component includes advanced features for re-use in custom developed applications, and it allows independent extensions by third parties without requiring its re-compilation. Illustrative examples on how to extend and re-use the library are provided as C# code projects. 相似文献
69.
70.
Davide A. L. Vignati Elisa Burdino Antonio M. Congiu Franco Cicala Michel Pardos Gianluigi F. Nieddu Giancarlo Ugazio 《Water, air, and soil pollution》2008,190(1-4):129-141
Sediment samples from 24 tributaries of the Po River (Italy) were screened for selected trace elements (Cd, Cu, Hg, Pb, and Zn) and extractable organic compounds; a proxy for contamination by organic microcontaminants. The toxicity of sediment extracts was evaluated using a battery of biotests (Dugesia gonocephala, Paracentrotus lividus, and Tamnocephalus platyurus). Contamination by trace elements (including very high Hg pollution – 4 to 16ppm total Hg – in one sub-basin) reached potentially harmful levels only in the sediments of four tributaries; while contamination by organic microcontaminants was present in most sub-basins. Sediments from most study sites did actually show signs of anthropogenic stress and were able to elicit a toxic response. A more detailed evaluation of sediment quality in the Po River tributaries seems to be urgently needed for developing the necessary remediation strategies. Research priorities should include more thorough testing of sediment toxicity, determination of metal background levels in the various sub-basins and a more detailed identification of the organic micropollutants of possible concern. 相似文献