Weed abundance and soil seedbank responses to tillage systems in continuous maize crops

Weed abundance in crops undergoes frequent changes, often due to changes in tillage practices. Annual species, with quick germination, a short vegetative stage, profuse seed production and long-lived seeds become problematic under zero-tillage systems. Portulaca oleracea L. and Amaranthus blitoides L. are widespread weeds in the Mediterranean area, prominent in irrigated crops. We studied the total weed abundance in the field, and specifically these two species (Portulaca oleracea and Amaranthus blitoides) with high frequency of occurrence in monoculture maize, from 2012 to 2014, in the field and soil seedbank. Results showed significant differences between zero-tillage (ZT) and conventional tillage (CT) systems on total weed abundance and relative abundance of Portulaca oleracea. Total weed abundance decreased in ZT plots (from 136 plants m^?2 to 25 and 46 plants m^?2, in 2013 and 2014 respectively). The same trend was observed in Portulaca oleracea recorded in ZT plots, but the abundance of Amaranthus blitoides did not vary in this system. Weed seedling germination and weed seed numbers both of total weed seedbank and Portulaca oleracea, were greater in ZT plots compared to CT, regarding Amaranthus blitoides seedling germination and seed count, the values did not increase with ZT, in continuous maize crops.     

Effect of nutrient solution salinity and ionic concentration on parsley (Petroselinum crispum Mill.) essential oil yield and content

The growth and essential oil (EO) production of parsley were evaluated in response to salinity and nutrient solution concentrations in a soilless culture. Parsley plants that were 60 days old were potted in a coconut fiber and peat moss medium and were treated with four different nutrient solutions, including T1, T2, T3 and T4. The T1 nutrient solution was the standard, the T2 and T3 solutions contained incremental macronutrient concentrations with an electrical conductivity (EC) of up to 2.2 and 3.2 dS m^?1, respectively, and the T4 solution was the same as T2 but with sodium chloride (NaCl) and an incremental macronutrient concentration with an EC of 3.2 dS m^?1. Next, these plants were grown for 90 days in a greenhouse with natural daylight in Nador, Morocco. Shoot and root growth significant decreased with increasing EC. However, the salinity that resulted from the addition of NaCl did not affect plant growth in the nutrient solutions. The optimum obtained growth and EO production were 1.2 and 2.2 dS m^?1, respectively. Consequently, the optimum EC value (based on the EO production) of parsley in the soilless culture was 1.2–2.2 dS m^?1.     

Short‐term degradation of semiarid grasslands—results from a controlled‐grazing experiment in Northern China

The assessment of grassland degradation due to overgrazing is a global challenge in semiarid environments. In particular, investigations of beginning steppe degradation after a change or intensification of the land use are needed in order to detect and adjust detrimental land‐use management rapidly and thus prevent severe damages in these sensitive ecosystems. A controlled‐grazing experiment was established in Inner Mongolia (China) in 2005 that included ungrazed (UG) and heavily grazed plots with grazing intensities of 4.5 (HG4.5) and 7.5 (HG7.5) sheep per hectare. Several soil and vegetation parameters were investigated at all sites before the start of the experiment. Topsoil samples were analyzed for soil organic C (SOC), total N (N_tot), total S (S_tot), and bulk density (BD). As vegetation parameters, aboveground net primary productivity (ANPP), tiller density (TD), and leaf‐area index (LAI) were determined. After 3 y of the grazing experiment, BD increased and SOC, N_tot, S_tot, ANPP, and LAI significantly decreased with increasing grazing intensity. These sensitive parameters can be regarded as early‐warning indicators for degradation of semiarid grasslands. Vegetation parameters were, however, more sensitive not only to grazing but also to temporal variation of precipitation between 2006 and 2008. Contrary, soil parameters were primarily affected by grazing and resistant against climatic variations. The assessment of starting conditions in the study area and the application of defined grazing intensities is essential for the investigation of short‐term degradation in semiarid environments.     

Heterogeneous aspects of lipid oxidation in dried microencapsulated oils

This work was aimed at studying lipid oxidation in dried microencapsulated oils (DMOs) during long-term storage. Samples were prepared by freeze-drying of emulsions containing sodium caseinate and lactose as encapsulating components. Evaluation of lipid oxidation was approached by quantitative analysis of nonvolatile lipid oxidation products and tocopherol. Lipid oxidation products were analyzed by separation of polar compounds by adsorption chromatography followed by HPSEC with refraction index detection for quantitation of oxidized triglyceride monomers, dimers, and oligomers. The analytical method applied enabled the detection of different oxidative patterns between the free and encapsulated oil fractions. The free oil fraction of DMOs showed a typical oxidative pattern for oils in continuous phase, which consisted of a clear induction period, in which hydroperoxides (oxidized triglyceride monomers) accumulated, before oxidation accelerated. The end of the induction period was marked by the total loss of tocopherol and the initiation of polymerization. On the contrary, the encapsulated oil showed a pattern characteristic of a mixture of oils with different oxidation status. Thus, high contents of advanced oxidation compounds (polymerization compounds) were detected when the antioxidant (tocopherol) was still present in high amounts. It is concluded that the encapsulated oil was comprised of oil globules with very different oxidation status. The results obtained in this study gave evidence of heterogeneous aspects of lipid oxidation in a dispersed-lipid food system.     

Use of Aloe vera gel coating preserves the functional properties of table grapes

Table grapes (Vitis vinifera L. cv. Crimson Seedless) were coated with Aloe vera gel according to our developed patent (SP Patent P200302937) and then stored for 35 days at 1 degrees C, and the subsequent shelf life (SL) was monitored at 20 degrees C. Uncoated clusters showed a rapid loss of functional compounds, such as total phenolics and ascorbic acid. These changes were accompanied by reduction of the total antioxidant activity (TAA) and increases in total anthocyanins, showing an accelerated ripening process. On the contrary, table grapes coated with Aloe vera gel significantly delayed the above changes, such as the retention of ascorbic acid during cold storage or SL. Consequently, Aloe vera gel coating, a simple and noncontaminating treatment, maintained the functional properties during postharvest storage of table grapes.     

Purification of xylitol obtained by fermentation of corncob hydrolysates

Hydrolysates obtained by autohydrolysis-posthydrolysis of corncobs were detoxified with charcoal, concentrated, supplemented with nutrients, and fermented with Debaryomyces hansenii. After biomass removal, the fermented media contained 0.1137 kg of nonvolatile components (NVC)/kg of liquor, which corresponded mainly to xylitol (0.6249 kg/kg of NVC) but also to minor amounts of inorganic components (measured as ashes), proteins, nonfermented sugars (xylose and arabinose), uronic acids, arabitol, and other nonvolatile components (ONVC). The media were subjected to further processing (sequential stages of adsorption, concentration, ethanol precipitation, concentration, and crystallization) to obtain food-grade xylitol. Adsorption experiments were carried out at various solid-to-liquor ratios. Under selected conditions (1 kg of charcoal/15 kg of liquors), the xylitol content increased to 0.6873 kg/kg of NVC, and almost total decoloration was achieved. The resulting liquor was concentrated by evaporation to increase its NVC content to 0.4032 kg/kg of liquor (corresponding to a xylitol concentration of 0.280 kg/kg of liquor), and ethanol was added to precipitate a part of the NVC (mainly proteins, but also uronic acids, ashes, and other nonvolatile compounds). Refined liquors (containing 0.7303 kg of xylitol/kg of NVC) were concentrated again, and ethanol was added (to reach 40-60% volume of the stream) to allow crystallization at -10 or -5 degrees C. Under selected conditions, 43.7% of xylitol contained in the initial fermentation broth was recovered in well-formed, homogeneous crystals, in which xylitol accounted for 98.9% of the total oven-dry weight. Material balances are presented for the whole processing scheme considered in this work.     

Time-resolved spectral studies of blue-green fluorescence of artichoke (Cynara cardunculus L. Var. Scolymus) leaves: identification of chlorogenic acid as one of the major fluorophores and age-mediated changes

Synchrotron radiation and the time-correlated single-photon counting technique were used to investigate the spectral and time-resolved characteristics of blue-green fluorescence (BGF) of artichoke leaves. Leaves emitted BGF under ultraviolet (UV) excitation; the abaxial side was much more fluorescent than the adaxial side, and in both cases, the youngest leaves were much more fluorescent than the oldest ones. The BGF of artichoke leaves was dominated by the presence of hydroxycinnamic acids. A decrease in the percentage of BGF attributable to the very short kinetic component (from 42 to 20%), in the shape of the BGF excitation spectra, and chlorogenic acid concentrations indicate that there is a loss of hydroxycinnamic acid with leaf age. Studies on excitation, emission, and synchronized fluorescence spectra of leaves and trichomes and chlorogenic acid contents indicate that chlorogenic acid is one of the main blue-green fluorophores in artichoke leaves. Results of the present study indicate that 20-42% (i.e., the very short kinetic component) of the overall BGF is emitted by chlorogenic acid. Time-resolved BGF measurements could be a means to extract information on chlorogenic acid fluorescence from the overall leaf BGF.     

Effect of fruiting body maturity stage on chemical composition and antimicrobial activity of Lactarius sp. mushrooms

The effects of fruiting body maturity on chemical composition and antimicrobial activity of the wild mushrooms, Lactarius deliciosus and Lactarius piperatus, were evaluated. Immature and mature samples were analyzed for proximate constituents (moisture, fat, crude protein, ash, carbohydrates), nutritional value, and individual composition in fatty acids and sugars. Protein content, MUFA (monounsaturated fatty acids), and PUFA (polyunsaturated fatty acids) percentages increased with the fruiting body maturity stage, while carbohydrate and SFA (saturated fatty acids) content decreased. The maturity stage did not significantly affect the individual sugar profile. The antimicrobial activity of the mushrooms was screened against Gram positive and Gram negative bacteria and fungi, and correlated to the amounts of phenols, flavonoids, ascorbic acid, beta-carotene, and lycopene present in the immature and mature fruiting bodies. Mature fruiting bodies with mature spores presented lower antimicrobial activity, which was in agreement with the bioactive compound content found in those samples.     

Defining the validity of a biochemical index of soil quality

 The native soils of Galicia (NW Spain) exhibit a biochemical equilibrium such that total soil N is a function of five biochemical and microbiological parameters: microbial biomass C, mineralized N, phosphomonoesterase, β-glucosidase and urease activities. To investigate whether the ratio of the total N calculated from biochemical soil properties (Nc) and the total N as measured by the Kjeldahl method (Nk; Nc/Nk) can be used as an index of soil quality, we determined these variables and consequently the ratio in three kinds of disturbed soils: an artificially Cu-contaminated soil, two lignite mine soils, and a number of arable soils. In none of the studied soils did the individual biochemical parameters respond consistently to the factors influencing soil quality, but in all cases soil degradation was reflected by the Nc/Nk value, which differed more or less markedly from 100%. Nc/Nk can therefore be used for the rapid evaluation of soil degradation, since it distinguishes among biochemically balanced soils, soils in a transient state of high microbiological and biochemical activity and degraded soils. It can also serve as a reliable basis for the rapid calculation of the "ecological dose" (ED₅₀) of soil pollutants. The use of Nc/Nk as an objective index of the biochemical quality of soils is recommended. Received: 20 December 1998     

1-methylcyclopropene increases storability and shelf life in climacteric and nonclimacteric plums

The effect of 1-methylcyclopropene (1-MCP) at three different doses (0.25, 0.50, and 0.75 microL L(-1)) on the ripening processes of a climacteric, cv. Santa Rosa, and a suppressed climacteric type, cv. Golden Japan, plum was studied. For both cultivars, positive effects were observed in terms of inhibition of ethylene production and delays of the physical, chemical, and biochemical changes associated with ripening. 1-MCP-treated plums were firmer with lower weight loss, reduced degrees Brix/titratable acidity ratios, and lower color changes during cold storage and subsequent shelf life at 20 degrees C than controls. For most factors, the effectiveness of 1-MCP was dose-dependent in Santa Rosa but dose-independent for Golden Japan.