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Polyploidization is regularly regarded as an important tool for the generation of innovative germplasm resources and plant breeding. In this study, autopolyploid switchgrass lines were produced from calli derived from immature inflorescence of tetraploid switchgrass ( Panicum virgatum L.), both lowland cv. Alamo and Kanlow, and upland cv. Ranlow, through colchicine treatments. Ploidy levels of plantlets regenerated from the calli were screened by flow cytometry. Growth characteristics of the tetraploid and octoploid switchgrass cultivars were further investigated in a field experiment. Compared with the tetraploid plants of the three switchgrass cultivars, the corresponding octoploid plants showed significant reduction in plant height, number of tillers per plant and fresh matter, but an increase in leaf length and width.

Grass hedges provide an efficient way to prevent soil and water loss on sloping croplands in numerous countries throughout tropical and subtropical regions. However, the effects of grass hedges on sloping land are still not well understood in temperate regions where there is severe soil and water loss. Therefore, the soil and water conservation benefits of two native grass hedges, Pennisetum alopecuroide ( Pennisetum alopecuroides (Linn.) Spreng.) and Arundinella hirta ( Arundinella hirta (Thunb.) C. Tanaka), were investigated using simulated rainfall with different slope gradients (5, 10, 15 and 20%), rainfall intensities (14, 22, 36 and 63 mm h − 1 ), and coverage of alfalfa ( Medicago sativa L.) on sloping lands of northern China. The results showed that Pennisetum hedges were more efficient in controlling soil and water loss compared with Arundinella hedges, possibly due to the more numerous, finer, and deeper roots in Pennisetum hedges. Overland flow and soil loss in sloping cropland were decreased by 52% and 75%, respectively, using Pennisetum hedges and 29% and 52%, respectively, using Arundinella hedges. The contribution of independent variables to overland flow followed the order rainfall intensity > coverage of alfalfa > type of grass hedges > slope gradient. The contribution to soil loss followed the order slope gradient > types of grass hedges > coverage of alfalfa > overland flow > rainfall intensity. Tillering ability and root characteristics should be considered in the selection of grass species when designing grass hedges. These findings may be helpful in the remediation of serious soil and water losses on sloping croplands in northern China and similar regions.

SummaryCalamagrostis brachytricha Steud. (feather reed grass) and Festuca glauca Lam. (blue fescue) were grown in mini-lysimeters under four irrigation regimes based on maximum crop evapotranspiration [ETc; 100% ETc (control)], 75% ETc, 50% ETc, or 25% ETc in order to estimate potential water savings in landscape management. Plant responses showed that shoot width, the number of tillers, and shoot dry weights (DWs) in feather reed grass were affected by deficit irrigation, and that there were significant linear correlations between these measurements and irrigation regime. However, in 2006, none of these parameters showed any significant difference between 75% ETc irrigation and the 100% ETc control. In 2007, plant height and the number of tillers gave similar results. There were significant linear correlations between irrigation regime and shoot height, shoot width, and shoot DW in blue fescue plants in 2006 and in 2007, while plants irrigated at 75% ETc showed no significant differences from control 100...

Soil and water loss have become a critical problem on sloping croplands in Northern China. Vetiver grass (Vetiveria zizanioides (L.) Nash) hedges have been suggested to be effective in preventing soil and water in tropical and subtropical regions but appear to be ineffective in temperate regions because they cannot withstand the low temperatures in winter time. Here we evaluated the soil and water conservation function of two native grass hedges, Pennisetum alopecuroide (Pennisetum alopecuroides (Linn.) Spreng.) and Arundinella hirta (Arundinella hirta (Thunb.) C. Tanaka), in Northern China. Three hydrologically isolated plots were used to test each combination of hedges and slope gradients (5%, 10%, 15% and 20%) under different levels of rainfall intensities (i.e. 14, 22, 36 and 63 mm h−1). The experiments were carried out on a different type of croplands (i.e. soybean (Glycine max (L.) Merr.), winter wheat (Triticum aestivum L.), alfalfa (Medicago sativa L.), and no crops) alternatively in a four-year period (2006–2009). Comparing to the case of using no grass hedges, on average Pennisetum hedges reduced soil loss by 84% and overland flow by 68%, and Arundinella hedges reduced soil loss and overland flow by 55% and 38%, respectively. These results suggested that both Pennisetum and Arundinella hedges provided effective protection against soil and water loss, and Pennisetum hedges had almost doubled efficacies over Arundinella hedges. Their protection efficacies varied across different types of croplands. However grass hedges action alone, under the experimental conditions, did not provide sufficient protection under steep slope and intense rain conditions. It was found that the impact of grass hedges on the control of runoff and erosion is more significant than rain intensity and slope gradient. The influence of root architecture on overland flow was assessed. One empiric model was derived to describe the influence of the independent variables (including slope gradient, rainfall intensity, age and type of grass hedges, and type of crops) on overland flow and soil transport and simulated the extent of protection under the range of experimental conditions. These findings may be helpful in the remediation of serious soil and water losses on sloping croplands in northern China and similar regions.

The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles in air, which were synthesized by using the thermal reduction in the polyol solution. The rutile structure of the ruthenium oxide was proved by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The oxide has good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent. The assembling of the silane to the oxide surface was proved by Infrared (IR) absorption spectroscopy. By mixing the nanoparticles with poly(methylvinylsiloxane) (PMVS) silicone rubber, a composite filled with dispersive conducting phase was fabricated. The temperature dependent conductivity shows that the electron transportation through composite is mainly dominated by tunneling. The measurement of piezoresistance shows that the composite at low strain has high piezoresistance repeatability. The 3D reconstruction images of the composite filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites. The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence.

To achieve possible water savings in irrigation, the maximum crop evapotranspiration (ETc) of three perennial flower plants (Sedum spectabile, Iris tectorum, and Dianthus chinensis) commonly used for landscaping in Beijing, China was studied in 2006 and 2007 using mini‐lysimeters. The plants were provided sufficient water based on the ETc measurements. Although meteorological conditions differed significantly between 2006 and 2007, each species had similar evapotranspiration curves in both years. The reference evapotranspiration ET0 during the growth stage (May‐October) in the 2 years was similar, being 524.93 mm in 2006 and 572.15 mm in 2007. However, marked monthly variations were noted in ET0 as well as in crop coefficients Kc. Based on the precipitation, the plants required supplemental irrigation during September and October of 2006, and May, June, August, and September of 2007. Using 20 years’ average precipitation for further analysis, we estimated that the plants would require supplementa...

Moderate-density molecular maps were constructed for the genomes of Eucalyptus urophylla S. T. Blake and E. tereticornis Smith using RAPD markers and an interspecific cross between the two species. One hundred and eighty-three primers were employed to generate 245 and 264 parent-specific markers in E. urophylla and E. tereticornis, respectively, as well as 49 parent-shared markers. The normally segregating markers, including 208 (84.9%) specific to maternal E. urophylla, 175 (66.3%) to paternal E. tereticornis, and 48 shared by both parents, were used for framework map construction for each parental species. For maternal E. urophylla, the linkage map consisted of 23 linkage groups, 160 framework markers, and 60 accessory markers, defining a total map distance of 1504.6 cM and an average interval of 11.0 ± 8.07 cM. For paternal E. tereticornis, the linkage map contained 23 linkage groups, 126 framework markers, and 92 accessory markers, defining a total map distance of 1035.7 cM and an average interval of 10.1 ± 7.23 cM. Genome length was estimated at 1585.7 and 1507.5 cM for E. urophylla and E. tereticornis, respectively, indicating map coverage of 94.9 and 68.7% of the corresponding genomes. Construction of such maps will be valuable for quantitative trait loci (QTLs) detection, marker-assisted selection (MAS), comparative mapping, and whole genome based fingerprint characterization in Eucalyptus breeding programs.

Correctly quantifying the relationships between soil respiration and environmental factors and their sources of variability is essential to predict future carbon fluxes and climate feedback. Soil water conditions and soil temperature strongly affect soil respiration and the dynamics of soil organic matter. Despite this, simulation of soil respiration (Rs) based on soil temperature (Ts) and soil volumetric water content (θ) must still be improved, as demonstrated by its discrepant model performance among different seasons. With the objective of gaining a further understanding of the relationships of Rs with Ts and θ and providing an improved model to simulate Rs variations, we measured hourly Rs, Ts and θ using the chamber technique in artificial smooth brome grassland for analysis. We began by dividing the four seasons of a year according to the daily mean air temperature, followed by representing the seasonal variation of Rs, Ts and θ. We found that Rs correlated significantly with Ts in an exponential relationship and with θ in a parabolic relationship seasonally, where the determination coefficient of the Rs-θ relationship was significantly larger than that of the Rs-Ts relationship. We also discovered that the shape of the Rs-θ relationship was seasonally dependent because the optimal θ and the width of the peak Rs around the optimal θ were seasonally specific. Finally, by considering seasonality, the combinational simulation model explained more variation of soil respiration. Thus, seasonality should be considered for more reliable model simulations of soil respiration. These findings are relevant for more accurate predictions and modelling of soil respiration, particularly in temperate artificial grasslands with a continental monsoon climate, where the ‘Birch effect’ strengthens seasonality, and these findings further our understanding of changes in the rates of soil carbon losses as artificial grassland is established.

Awareness and concern for problems related to environmental quality are growing at a steady pace: climate change, biodiversity, soil fertility decay and above all food quality and pollution are everyday subjects for debates and discussions. The complexity of the problems and the uncertainty about many basic data quite often make discussions inconclusive; even indications issued by scientific authorities are sometimes misleading, and the problems are exacerbated by the frequent influence of ideological positions. In an endeavour to contribute to clarify agriculture-related environmental issues, a review is made here of the principles of sustainable agriculture and of the ways to deal with them. The need is emphasized for a system approach which is able to reconcile economic-productive, environmental and social aspects, the three ‘pillars’ of sustainability, permitting to consider simultaneously the numerous factors concurring to determine the most appropriate production strategy, and the necessary flexibility in selecting and combining such factors is also outlined. A critical overview is made of the possible options for improving the sustainability of the four principal groups of agricultural operations: cultivation, fertilization, irrigation and pest control. For each of them, the sustainability level of various possible courses of action is estimated as resulting from their expected impact on the three ‘pillars’ of sustainability and indications are given to avoid risks deriving to agricultural sustainability from misconceptions of non-scientific approaches, including some typical of organic farming. For cultivation, the adoption of some form of conservation tillage is suggested and the various possible options are critically examined. The conclusions for fertilization are that generally the best solution is a blending of organic and mineral fertilizers and that food quality is not influenced by the origin of the fertilizer. Criteria for optimizing irrigation system design and management are illustrated, with reference to energy input, soil protection against erosion and salinity build-up, and reduction in production risks. For pest control, integrated pest management approaches including proactive activities and the parallel reduction to the possible extent of synthetic pesticide applications result in the most sustainable solution. Emphasis is given to those aspects of sustainability, such as soil and water conservation, energy savings, CO2 balance, which are often overlooked, yet are an important component of sustainability. It is argued that an effective, long-term sustainability of agriculture must primarily gain farmers acceptance and therefore selected solutions must guarantee profit levels and productivity while not increasing risks. It is concluded that since the concept of sustainability is fundamentally dynamic, site- and time-specific, proposed solutions are expected to be flexible, custom-tailored for the single farms and open to technological and scientific progress, avoiding any pre-concocted paradigm and dogmatism; as a consequence, it is evidenced that some rigid principles typical of organic farming are not compatible with sustainable agriculture.

A new conductive rubber composite was fabricated by mixing the ruthenium oxide nanoparticles with silicone rubber. The ruthenium oxide nanoparticles were synthesized by oxidation of metallic ruthenium nanoparticles, which were made using a polyol method. The size of the ruthenium oxide can be tuned by changing the annealing duration in inert atmosphere. It was found that the composite filled with ruthenium oxide of the less size presents more stable piezoresistance recurrence. Based on the random resistor network model and transfer matrix approach, a numerical calculation of the tunneling bonds resistor lattice was conducted to simulate the percolation and piezoresistance behavior of the composite. The simulation shows that the particle size and distribution have strong influences on both the percolative conductivity and the piezoresistance sensitivity.

This paper presents a robust watermark detector in the discrete cosine transform (DCT) domain. First, the watermark detection problem is formulated as a binary hypothesis testing problem according to the statistical inference. Then, the alternative current DCT coefficients are statistically modeled by symmetric alpha-stable distributions. More specifically, the scale mixture of Gaussians as an analytical approximation of alpha-stable distribution is employed. Finally, based on the theory of statistical inference and weak signal detection in non-gaussian noise, a robust blind detection algorithm is derived. And the validity of the detector is also tested.

Moderate-density molecular maps were constructed for the genomes of Eucalyptus urophylla S. T. Blake and E. tereticornis Smith using RAPD markers and an interspecific cross between the two species. One hundred and eighty-three primers were employed to generate 245 and 264 parent-specific markers in E. urophylla and E. tereticornis, respectively, as well as 49 parent-shared markers. The normally segregating markers, including 208 (84.9%) specific to maternal E. urophylla, 175 (66.3%) to paternal E. tereticornis, and 48 shared by both parents, were used for framework map construction for each parental species. For maternal E. urophylla, the linkage map consisted of 23 linkage groups, 160 framework markers, and 60 accessory markers, defining a total map distance of 1504.6cM and an average interval of 11.0 +/- 8.07 cM. For paternal E. tereticornis, the linkage map contained 23 linkage groups, 126 framework markers, and 92 accessory markers, defining a total map distance of 1035.7 cM and an average interval of 10.1 +/- 7.23 cM. Genome length was estimated at 1585.7 and 1507.5 cM for E. urophylla and E. tereticornis, respectively, indicating map coverage of 94.9 and 68.7% of the corresponding genomes. Construction of such maps will be valuable for quantitative trait loci (QTLs) detection, marker-assisted selection (MAS), comparative mapping, and whole genome based fingerprint characterization in Eucalyptus breeding programs.