ABSTRACT. The effect of different light regimes (100, 85 and 70 % solar exposition) on coffee plants (Coffea arabica L. var. Caturra) was studied. There was an overall effect of solar exposition levels on growth at different crop growth stages, plant height and stem diameter being the most affected varia- bles with higher values in 85 % solar exposition. Relativewatercontent showed daily variations with minimum values at midday for higher exposition level treatments. Transpiration was slightly higher in 100 % level at 11:00 h, and an increased chlorophyll a and b content was observed in 85 % solar exposition, while carotene content was similar in the three levels. The total chlorophyll a+b showed a highest value in the 85 % level of solar exposition. Results indicated some adaptability features of coffee plants to slight shade conditions, because of the constancy observed for chlorophyll a/b ratio among solar radiation exposition levels, and the highest vegetative growth showed in moderated shade (85 % solar exposition).
B(OH) 3 and 100 mM NaCl and 0.08 mM B(OH) 3 ) were applied on days 23 and 34, respectively, before the final solution was applied. The plants were watered daily with 400 mL of solution per pot, and the pots were washed with purified water every third day to avoid concentrating the salts. These chemical compounds were added to Jensen’s medium. The eight accessions were identified according to their place of origin as Chiza, San Pedro I (SPI), Taltal, Azapa, San Pedro II (SPII), Frantoio and Lluta. Five replicates were used for each accession, with one plant per replicate. The treatments were applied for 132 days. The param- eters measured included vegetative growth, leaf dry weight, relativewatercontent (RWC), water potential ( Ψ w ) and the B and Cl - contents of the
We investigated the physiological responses of two epiphytic orchids under three light regimes of 20, 50, and 70% of total daily radiation under drought and rewatering conditions. Stanhopea tigrina was the one more affected because it exhibited strong photoinhibition and reduction of both electron transport rate and nocturnal acidity under drought and high radiation. However, this species maintained relatively high relativewatercontent (RWC) values and underwent osmotic adjustment during the drought period and recovered photosynthetic variables during watered period. Prosthechea cochleata maintained similar water and photosynthetic responses to light conditions during the drought period and was more tolerant than S. tigrina. Principal component analysis provided evidence that water variables, such as RWC and succulence of both leaf and pseudobulb, were the most important variables for both species. Our results suggest that S. tigrina is more sensitive to drought than P. cochleata, and could be more affected by global warming.
Present production and processing practices of the mentioned Capsicum spp. in Bolivia and Peru remains traditional, , where the farmers spread fruits on their fields after harvest and leave them exposed until they are dry, which contributes to the development of undesirable microorganisms that pose health risks due to the production of toxic substances namely mycotoxins (Erdogan, 2004). Tropical and subtropical region are optimal areas for the development of this fungus due to the climatic characteristics as for example high temperature and relative humidity (Martins, et al., 2001, Moss, 2002). Several studies have documented the occurrence mycotoxins presence in dried capsicums(Almela, et al., 2007, Aydin, et al., 2007, O' Riordan and Wilkinson, 2008) .
In all cases, the shapes of the heat evolution curves measured by isothermal conduction calorimetry (Figure 1A) are consistent with what has been reported previously for silicate- activated slags (Fernández-Jiménez and Puertas, 1997, Shi, 1997, Bernal et al., 2014). A pre- induction period (first peak) is observed during the first hours of reaction (2.5 h), followed by a short induction period, and a high intensity acceleration and deceleration period (second peak) corresponding to the nucleation, growth and precipitation of reaction products. The content of water in the mix clearly modifies the onset time, intensity and duration of the peak assigned to the acceleration/deceleration period, so that a w/b ratio of 0.44 promotes the highest heat release over the testing time, followed by pastes formulated with w/b ratios of 0.48 and 0.40 respectively. Comparable heats of reaction (Figure 1B) are identified in the first 7 h of testing in pastes with w/b ratios of 0.40 and 0.48. At all times of reaction beyond 4 hours (the onset of the acceleration period for the sample with w/b = 0.44), significant differences in the cumulative heat of reaction are observed as a function of the watercontent, so that higher reaction heats are observed at all testing times for pastes with w/b = 0.44, followed by pastes with a w/b ratio of 0.48, and the paste with w/b = 0.40 showing the lowest heat release. This is particularly notable when considering that the heat release data are normalised to the total paste mass, meaning that the heat release per mass of slag in the mixes is actually much lower for the paste with the lowest watercontent, indicating a much lower degree of reaction in this system. The w/b 0.44 sample still shows a higher maximum heat release rate and a higher reaction heat than the w/b 0.48 mix when these data are compared on a basis of slag mass, indicating this effect must be associated with a chemical one.
In this study the effect of modifying the watercontent of an alkali-activated slag binder was assessed, in terms of the kinetics of reaction and the structural development of the material. The results reveal that there is not a systematic correlation between the watercontent of the mix and the rate of reaction, indicating that there is an optimal value that favours dissolution of the slag and precipitation of reaction products in these binders. A higher watercontent reduced the crystallinity and density of the reaction products, especially at advanced age. Small changes in the watercontent can have a significant impact on the compressive strength development of alkali-silicate activated slag mortars, suggesting that when producing materials based on alkali-activated binders, it is essential to carefully control the watercontent.
addition, the existence of suspended organic solids in liquid can enhance the solubility of VOCs of low water solubility. The sorption of VOCs in activated sludge biomass has been an investigation topic in many studies. The accumulation of some VOCs or hazardous pollutions by live (Smith et al., 1993; Wang and Grady Jr., 1995), dead (Dobbs et al., 1989; Tsezos and Wang, 1991), and pasteurized (Moretti and Neufeld, 1989; Dobbs et al., 1995) microorganisms has been investigated. By the sorption of the biomass, the total VOC contents in the liquor will be raised, that is, the existence of biomass will increase the apparent solubility of VOCs in the liquor.
Plant internal water potential is a consequence of the soil–plant atmospheric continuum and consists of the ten- sion caused by the water pressure deficit of the atmosphere, regulative processes of leaves, general flow regulation resistances and the soil water potential (Philip 1966; Duhme and Richter 1977; Kozlowski et al. 1991; Kramer and Boyer 1995; Donovan et al. 2003). It is a dependable measure of plant and soil water status and quickly mea- sured directly in the field, a great advantage especially for plant comparison (Slatyer 1967; Sala et al. 1981; Pallardy et al. 1991; Kramer and Boyer 1995; Mitlo¨hner 1998; Vertovec et al. 2001; Donovan et al. 2003). The water balance of a plant becomes negative when the uptake of water is insufficient to meet the requirements of transpi- ration (Sellin 1998) and plants begin to suffer water stress. Declining water potentials indicate water stress, which can be divided into static stress and dynamic stress. The first one is caused by low water availability in the soil, and the second one results from the resistance of water flow through the plant due to transpirational water loss from foliage, so plant water potentials decline (Tyree and Ewers 1991). The dynamic of leaf water potentials at a certain daytime (W wmd , in our case at midday) can be treated as the
not only exhibited the highest absorbance intensity at about 500 nm, but also reported the highest diameter (103 nm), the optimum length (0.9 µm), and the largest crystallite size (36 nm) among all of the modified samples. EDX analysis revealed that the vanadium content in this sample was equal to 9.08 wt %. In sum, the photocatalytic properties of these highly efficient nanocomposites, obtained through the most suitable method (electrochemical technique), permit new insights into the exploitation of industrially oriented applications, for instance, photocatalytic devices for air purification. The presented materials are photoactive under a low powered light source, and thus, the use of low cost light-emitting diodes (LEDs) as an irradiation source can significantly reduce the cost of photocatalytic air treatment processes, which is consistent with the principles of green chemistry.
manage the water resources in these zones, it is important to quantify the evaporation fluxes. Evaporation from saline soils is a complex process that couples the movement of salts, heat, liquid water and water vapor, and strongly depends on the soil watercontent. Precipitation/dissolution reactions can change the soil structure and alter flow paths, modifying evaporation flows. In this research, the effect of sodium adsorption ratio (SAR) on soil hydraulic properties was evaluated experimentally. HYDRUS-1D was used to represent the movement of liquid water and water vapor in a saline soil column using experimental results. To determine the effect of SAR on evaporation fluxes, soils with different SAR were used in numerical simulations. It was found that for higher sodium concentrations, the soil increase its water retention capacity, increasing the cumulative evaporation. Also, it was found that evaporation fluxes increase salt concentration in the region near the soil surface, changing the soil’s water retention capacity in those zones. Then, the movement of salts causes differences in evaporation fluxes. It is thus necessary to incorporate salt precipitation/dissolution and its effects on the retention curve to correctly simulate evaporation in saline soils.
3. The guidance being created uses as its basis the guidelines developed during the Expert Meeting on Methods and Guidelines for the Rapid Assessment of Biological Diversity of Inland Water Ecosystems, which was held in Montreal from 2 to 4 December 2002. The draft guidance, which is contained in this document, is currently under review by a Liaison Group. This group, which is operating electronically through a listserv and a restricted web site, has representatives from the following organizations or assessments: The Global International Waters Assessment (GIWA); Marine Rapid Assessment Programme of Conservation International; Atlantic and Gulf Rapid Reef Assessment (AGRRA); Ramsar Convention; UNEP-WCMC; Northwest Hawaiian Islands Rapid Reef Assessment (NOW-RAMP); The Intergovernmental Oceanographic Commission (IOC) of UNESCO; The Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (GPA); Land-Ocean Interactions in the Coastal Zone (LOICZ); Reef Check; Reefs at Risk of the World Resources Institute; Coral Reef
The plant microbial fuel cells (PMFCs) used in this study consisted of 450 mL plastic pots (with holes at the bottom to allow free drainage) filled with 400 mL of plant growth substrate. This growing media was collected in May 2013 from a green roof under construction (i.e., before the plants were established) on the Campus San Joaquín at the Pontificia Universidad Católica de Chile (PUC) in Santiago, Chile (Figure A.1). It was composited of a mineral matrix of sand, silt, and clay amended with organic matter (Table 2-1). Electrodes made of a circular graphite fiber felt of 92 mm in diameter and 6 mm thick (MudWatt, California, USA) were initially installed; one was buried at a depth of 7 cm and the other one was placed on the substrate surface. The buried electrodes were inoculated with mud from a pond used as a water supply for irrigation located at the same campus. Each PMFC reactor contained one of the seven Sedum species used in this study (S. album, S. hybridum, S. kamtschaticum, S. reflexum, S. rupestre, S. sexangulare and S. spurium) and one pot was left without a plant as a control (Fig. 2-1).
At the time of maximum photosynthetic activity in lea- ves exposed and unexposed, N-S and E-W had the highest values of potential, differing markedly from the two inter- mediate orientations, with an average increase, for the three years of study, of 16 and 17% for sunny and shaded leaves. In early morning, the E-W direction intercepts the least amount of direct solar radiation when compared to N-S, N+45 and N+20 (Champagnol, 1984), which determines the highest level of moisture in leaves. Moreover, N-S reaches punctual values of radiation interception higher than those at N+45 and N+20, but these last orientations accumulate more radia- tion throughout the cycle and achieve higher levels of stress, so they have more difﬁculties both in rehydration and in rea- ching the harvest with an adequate water level in the plant. Direct solar radiation and vapor pressure deﬁcit, determine the water demand of the leaf (its transpiration is regulated by the opening and closing of stomata), linked to its micro- climate, (Choné et al., 2000; Deloire et al., 2004). In gene- ral, at the time of maximum net photosynthesis differences between treatments for both sides of the trellis were clearer.
Maldonado et al. (2005) found that medium-sized fish farms located on semi exposed western Mediterranean coasts have fewer environmental impacts than traditional fish farms located in shallow, sheltered sites. Impact characterization in these new farms may require refinement of the standard approach to deal with rapid dispersal of effluents and sub-lethal levels of environmental disturbance. Similar results were found in small farms in this study. The changes in redox potential showed a linear relationship with the organic carbon concentration in the sediments of sea cages area as well as water temperature. In a study conducted by Holmer & Kristensen (1994) on sediment metabolism, a strong correlation was observed in a sea cage farm between total anaerobic metabolism (TCO 2 production) and input of feed pellets and the water temperature explained the 40% of this behavior. Various studies had reported that the input of organic matter affects the seasonal variation of the major biochemical cycles (Hargrave et al. 1993). Pawar et al. (2002) found that the acid volatile sulphide -S content is strongly correlated with the water temperature and the seasonal organic carbon input. In this study, the redox potential in water and the organic carbon content in sediment were strongly correlated with water temperature, this can be explained due the increase of fish metabolism generated by high temperatures in summer causing a higher demand of food input, resulting in an increase of the organic carbon matter quantity in the sediment and provoking higher sulfate reduction rates and an increase of organic carbon content in the sediment and a decrease of redox potential in the column of water. The redox potential was highly correlated with the organic carbon in sediment, than water temperature. Thus, among the indicators used to evaluate environmental impact of the sea cage fish farm, redox potential proves to be a better indicator.
Sorption models have been evaluated rigorously by Simpson (1973) for temperatures between 0 and 100°C. Unfortunately, these models cannot be applied directly to processes such as the hot pressing of wood-based composite panels (García 2002, Humphrey 1989) and high temperature wood drying due to temperatures higher than 100°C reached in these processes. A modification of Bradley’s model to determine relative vapor pressure as a function of wood moisture content and temperature has been extensively used for wood drying at temperatures below 100ºC (Tremblay 1999, Defo 2000, Turner 1996). Representative conditions for high-temperature wood drying include temperatures up to 130°C and vapor pressure up to 250 kPa (Perré, 1996). For the hot-pressing of wood-based panels, temperatures vary typically from 150 to 220°C and vapor pressure can reach values up to 150 kPa depending on the type of panel. Unfortunately, there are no studies which indicate a sorption model appropriate for temperature and vapor pressure conditions encountered in these processes (Dai and Changming , 2004). Therefore, there is a major interest in understanding and determining the most appropriate model
The PMFCs performance showed differences in relation to previous studies in two aspects, that is, start-up time and radiation. The start-up period was shorter than those reported under laboratory conditions, where the start-up time was observed in more than 100 days [9,21]. This difference in the start-up may be due to the fact that the PMFCs tested in this study were installed on a green roof built about a year before the experiment, which could lead to a greater number of roots and therefore a higher organic matter content available for microorganisms, allowing the fast establishment of electroactive microorganisms (EAMs) in anodes. The solar radiation during the testing period was greater than that previously used in the laboratory for PMFC experiments, which does not exceed 596 ± 161 µ mol m −2 s −1 [22,23]. However, a relationship between solar/light radiation and current was not observed in contrast to previous PMFC studies conducted with wetland plants [24,25]. There seems to be a slight increase in current during the night, which could be related to variations in the moisture content allowing an increase of ion mobility through the substrate or affecting the release of exudates from the roots. Previous studies had reported that the exudation of carbohydrates increases with the soil watercontent . Crassulacean acid metabolism of Sedum might also lead to exudation of organic compounds in darkness periods when carbon is fixed. Hence, the plant metabolism can affect the exudation response to different factors, for example light intensity . However, to the best of our knowledge, in the literature, there is no conclusive evidence related to this process. Further detailed research is needed to understand the root exudation of CAM species.
to a two-way analysis of variance (ANOVA) at each sampling date. The differences were validated using the Tukey’s honestly significant differences (HSD) test and were considered statistically significant at p≤0.05 for all pairwise comparisons (Steel and Torrie, 1980). On a seasonal basis, correlation coefficients between morning and afternoon soil respiration rates and environmental variables (soil temperature, soil watercontent, absolute maximum air temperature, maximum mean air temperature, monthly mean air temperature, minimum mean air temperature, absolute minimum air temperature and monthly precipitation) at each land use were quantified by the Spearman’s rank order correlation analyses since the null hypothesis of normality was rejected at p<0.05 (Steel and Torrie, 1980; Ott, 1993). Linear regression analyses were performed between soil respiration rate and morning and afternoon soil temperature at each land use. All statistical methods were applied according to the SPSS (Statistical Package for the Social Sciences) software package (standard released version 9.0 for Windows, SPSS Inc., Chicago, IL).
of the sediments in the vials, caused by the addition of HCl, the water was siphoned and the vials with the wet sediments were oven dried at 55-60 ºC for 24 to 48 h and then weighed. From these weights, the amount of water and the mass of soil contained in suspension in the vials were calculated and extrapolated to the flood volume of the tanks. Thus, total water and soil losses were calculated for each erosive rainfall. The procedures for collecting samples in the field, their processing in the laboratory, and the calculation of the total losses followed the methodology suggested by Cogo (1978). In the field, other samples of runoff were collected in vials of the same volume for further chemical analysis. After sedimentation without chemical addition, the water was siphoned, filtered, and conditioned in a refrigerator, and the sediments were air dried and conditioned for further chemical analysis.