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Soils with scarce plant covering are very susceptible to water and wind erosion. Two species recommended for permanent cover of soil are Lotus creticus creticus and Cynodon dactylon. The performance of both species cultivated in p...
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Soils with scarce plant covering are very susceptible to water and wind erosion. Two species recommended for permanent cover of soil are Lotus creticus creticus and Cynodon dactylon. The performance of both species cultivated in pure stands and in mixture and with 2 watering regimes, high (12.64 L/bag) and low (8.36 L/bag), was analysed in polyethylene bags between March and July in greenhouse conditions. With low watering the growth of both species was lower but mortality of plants was not observed. Growth of stems in L. creticus and stolons in C. dactylon did not stop with low watering. The growth of C. dactylon was higher than that of L. creticus at both watering regimes. Total root and green shoot biomass of each species was affected by watering. Green leaf area, root weight ratio, root hydraulic resistance, and watering efficiency (g biomass/L watering) differed with the combination of species. Green leaf area, root hydraulic resistance, and watering efficiency were higher in C. dactylon than in L. creticus. Root weight ratio was higher in L. creticus than in C. dactylon, but the specific length and area of roots were higher in C. dactylon than in L. creticus. Net photosynthesis rate of each species was only affected by watering regime. Performance of both species was not affected by the mixture and it has the potential to be a successful ground cover.
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Phytoremediation technologies must tolerate and degrade mixtures of contaminants, as most contaminated sites contain mixtures of compounds. This study assessed the ability of plant-bacteria associations to degrade mixtures of mono...
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Phytoremediation technologies must tolerate and degrade mixtures of contaminants, as most contaminated sites contain mixtures of compounds. This study assessed the ability of plant-bacteria associations to degrade mixtures of mono-and dichlorinated benzoic acids. Sixteen forage grasses and combinations of these grasses with several bacterial inoculants were screened of growth in soil contaminated with various concentrations of mono- or dichlorinated benzoic acids. Dahurian wild rye (Elymus dauricus) inoculated with a combination of Pseudomonas aeruginosa strain R75 and Pseudomonas savastanoi strain CB35 reduced 3- chlorobenzoic acid (3CBA) levels in soil by 74/100 (i.e., 583 to 149 mg/kg).
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Phytoseiulus persimilis is a predatory mite that in absence of vision relies on the detection of herbivore-induced plant odors to locate its prey, the two-spotted spider-mite Tetranychus urticae. This herbivorous prey is feeding o...
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Phytoseiulus persimilis is a predatory mite that in absence of vision relies on the detection of herbivore-induced plant odors to locate its prey, the two-spotted spider-mite Tetranychus urticae. This herbivorous prey is feeding on leaves of a wide variety of plant species in different families. The predatory mites respond to numerous structurally different compounds. However, typical spider-mite induced plant compounds do not attract more predatory mites than plant compounds not associated with prey. Because the mites are sensitive to many compounds, components of odor mixtures may affect each other's perception. Although the response to pure compounds has been well documented, little is known how interactions among compounds affect the response to odor mixtures. We assessed the relation between the mites' responses elicited by simple mixtures of two compounds and by the single components of these mixtures. The preference for the mixture was compared to predictions under three conceptual models, each based on one of the following assumptions: (1) the responses elicited by each of the individual components can be added to each other; (2) they can be averaged; or (3) one response overshadows the other. The observed response differed significantly from the response predicted under the additive response, average response, and overshadowing response model in 52, 36, and 32% of the experimental tests, respectively. Moreover, the behavioral responses elicited by individual compounds and their binary mixtures were determined as a function of the odor concentration. The relative contribution of each component to the behavioral response elicited by the mixture varied with the odor concentration, even though the ratio of both compounds in the mixture was kept constant. Our experiments revealed that compounds that elicited no response had an effect on the response elicited by binary mixtures that they were part of. The results are not consistent with the hypothesis that P. persimilis perceives odor mixtures as a collection of strictly elemental objects. They suggest that odor mixtures rather are perceived as one synthetic whole.
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Phytoseiulus persimilis is a predatory mite that in absence of vision relies on the detection of herbivore-induced plant odors to locate its prey, the two-spotted spider-mite Tetranychus urticae. This herbivorous prey is feeding o...
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Phytoseiulus persimilis is a predatory mite that in absence of vision relies on the detection of herbivore-induced plant odors to locate its prey, the two-spotted spider-mite Tetranychus urticae. This herbivorous prey is feeding on leaves of a wide variety of plant species in different families. The predatory mites respond to numerous structurally different compounds. However, typical spider-mite induced plant compounds do not attract more predatory mites than plant compounds not associated with prey. Because the mites are sensitive to many compounds, components of odor mixtures may affect each other's perception. Although the response to pure compounds has been well documented, little is known how interactions among compounds affect the response to odor mixtures. We assessed the relation between the mites' responses elicited by simple mixtures of two compounds and by the single components of these mixtures. The preference for the mixture was compared to predictions under three conceptual models, each based on one of the following assumptions: (1) the responses elicited by each of the individual components can be added to each other; (2) they can be averaged; or (3) one response overshadows the other. The observed response differed significantly from the response predicted under the additive response, average response, and overshadowing response model in 52, 36, and 32% of the experimental tests, respectively. Moreover, the behavioral responses elicited by individual compounds and their binary mixtures were determined as a function of the odor concentration. The relative contribution of each component to the behavioral response elicited by the mixture varied with the odor concentration, even though the ratio of both compounds in the mixture was kept constant. Our experiments revealed that compounds that elicited no response had an effect on the response elicited by binary mixtures that they were part of. The results are not consistent with the hypothesis that P. persimilis perceives odor mixtures as a collection of strictly elemental objects. They suggest that odor mixtures rather are perceived as one synthetic whole.
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Key message Our study shows for the first time a complete guabiroba micropropagation system with acclimatized plants. BA was the best plant growth regulator for multiplication and IBA for rooting. Campomanesia xanthocarpa O. Berg ...
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Key message Our study shows for the first time a complete guabiroba micropropagation system with acclimatized plants. BA was the best plant growth regulator for multiplication and IBA for rooting. Campomanesia xanthocarpa O. Berg (Myrtaceae), popularly known as guabiroba, is a woody species native to Brazil, important for its potential as a medicinal plant and fruit tree. For the first time, this study shows a complete system of micropropagation for this species. For this, nodal segments with two axillary buds each were used as starting material. Plant Preservative Mixture (TM) (0.1%) added to culture media was efficient in controlling contamination throughout the culture process. Two formulations of culture medium were compared for in vitro establishment. 2-Isopentenyladenine, 6-benzyladenine, kinetin and zeatin were tested during the multiplication step. Woody plant medium (WPM) was appropriate for all culture steps and, during the multiplication process, 2.2 mu M BA induced the best numbers of new shoots per explant during three subcultures (3.0-3.5 per month). For rooting of microcuttings, a rate of 53% was reached in the WPM supplemented with 4.9 mu M indol-3-butyric acid. A plastic box containing a mixture of commercial substrate and vermiculite (1:1 v/v) was used for plantlet acclimatization, allowing 52% of survival after two months. In conclusion, a complete micropropagation protocol was developed providing healthy plants. Further studies are needed to improve multiplication and survival rates.
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This two-year study focused on mechanisms of nutrient removal efficiency and variation in this efficiency in a pilot-scale natural wetland with different macrophyte species. Effects of plant harvesting and the differences among pl...
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This two-year study focused on mechanisms of nutrient removal efficiency and variation in this efficiency in a pilot-scale natural wetland with different macrophyte species. Effects of plant harvesting and the differences among plant species (Ceratophyllum demersum, Nelumbo nucifera, Zizania latifolia, Hemarthria sibirica, Phragmites communis, and Typha orientalis) were investigated. Results show that the mean retention of total nitrogen (N), total dissolved N, ammonia N, nitrite N, total phosphorus (P), total dissolved P, and phosphate P in the second year was generally lower than that found in the first year. Harvest of above-ground macrophytes had a beneficial effect on retention capacity, especially for total dissolved N and ammonia N, whereas an increase in nutrient concentration was observed in zones that were not harvested. The total N removal efficiency had a positive relationship with inflow loading. A mixture of Z. latifolia and T. orientalis demonstrated the best potential for both N and P retention.
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Silage making is discussed broadly. Crops suitable for silage making include maize, sunflower, carrots with tops, top cabbage leaves, pea haulm, oat-vetch mixture, grass mixture and weeds (group 1); and clover, lucerne, vetch and ...
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Silage making is discussed broadly. Crops suitable for silage making include maize, sunflower, carrots with tops, top cabbage leaves, pea haulm, oat-vetch mixture, grass mixture and weeds (group 1); and clover, lucerne, vetch and wild plants (group2). Group-2 plants are usually added at 30-40% to group-1 plants during silage making. Moisture content of the ensiling material should be 70-85%. Various combinations of material could be used for silage making. The most valuable are mixed silages and are useful feeds for many types of farm animals.
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Abstract Recent studies have demonstrated that cultivar mixtures can reduce aphid plant acceptance and population development. It is still unknown as to which underlying mechanisms may contribute to this phenomenon. We investigate...
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Abstract Recent studies have demonstrated that cultivar mixtures can reduce aphid plant acceptance and population development. It is still unknown as to which underlying mechanisms may contribute to this phenomenon. We investigated the effects of volatile interactions between undamaged barley cultivars on aphid feeding behavior and performance in the laboratory. Spring barley (Hordeum vulgare L.) cultivar Salome was exposed to volatiles from Fairytale (SeF), Anakin (SeA), or clean air (Se0). We used an electrical penetration graph to test the effect of exposure to neighbor volatiles on the feeding behavior and performance of bird cherry-oat aphids (Rhopalosiphum padi L.). We also assessed aphid relative growth rate, intrinsic rate of increase, and development time on exposed and unexposed Salome plants. Aphids spent significantly longer time on epidermis and mesophyll plant tissues on SeF than Se0, and no difference was observed between SeA and Se0. Significant decreases in the duration of phloem ingestion and phloem sustained ingestion were recorded in SeF showing that volatile-induced effects cause difficulty for aphids to feed. However, no differences in these variables were detected between SeA and Se0. We also observed reduced aphid relative growth rate and intrinsic rate of increase on SeF compared to Se0 and SeA. Our study demonstrated that, in a specific combination, exposure of one barley cultivar to volatiles from another one can change aphid feeding behavior and performance, probably due to changes in host plant properties/quality. Our results provide an insightful explanation of mechanisms responsible for the reduced aphid population development previously observed in the field.
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Understanding how the spatial organization of diversified plant communities alters their performance is an important step in designing and managing diversified agroecosystems. The high level of spatial heterogeneity in tropical ag...
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Understanding how the spatial organization of diversified plant communities alters their performance is an important step in designing and managing diversified agroecosystems. The high level of spatial heterogeneity in tropical agroforests makes this task challenging. In 19 agroforestry plots in Talamanca (Costa Rica), we analyzed the effect of the structure of the plant community in the neighborhood of each individual cacao tree and banana plant on their growth and yield parameters. We developed an individual-based analysis in two steps. First, we selected without a priori the distance at which the number of neighboring plants of a given functional group (banana plants, cacao trees, fruit trees, or wood trees) best explained the proportion of attainable yield (PAY) of cacao and banana plants. In a second step, we tested the significance of the abundances of the four groups of plants in a complete model that predicted the PAY of banana and cacao plants. The abundance of neighboring plants did not increase banana PAY except in the case of other banana plants, suggesting that banana plants yield better when aggregated. All other groups of plants tended to reduce both banana and cacao PAY. In the case of wood trees, these trends were not significant. Interestingly, our results suggests that it is possible to associate banana plants and cocoa trees to moderate densities of other plants without reducing their yield. The two complete linear models predicted about 60 % of the variance of the average response of the PAY to the neighboring plant assemblage. We suggest that in the future, it would be important to differentiate processes (resources partitioning, pest and diseases) inside our statistical approach. While requiring much more data, it could be useful to address the effect of cultural practices.
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The biotic ligand model (BLM) is a bioavailability model for metals based on the concept that toxicity depends on the concentration of metal bound to a biological binding site; the biotic ligand. Here, we evaluated the BLM to inte...
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The biotic ligand model (BLM) is a bioavailability model for metals based on the concept that toxicity depends on the concentration of metal bound to a biological binding site; the biotic ligand. Here, we evaluated the BLM to interpret and explain mixture toxicity of metals (Cu and Zn). The mixture toxicity of Cu and Zn to barley (Hordeum vulgare L.) was tested with a 4 days root elongation test in resin buffered nutrient solutions. Toxicity of one toxicant was tested in presence or absence of a low effect level of the other toxicant or in a ray design with constant toxicant ratios. All treatments ran at three different Ca concentrations (0.3, 2.2 and 10 mM) to reveal ion interaction effects. The 50 % effect level (EC50) of one metal, expressed as the free ion in solution, significantly (p < 0.05) increased by adding a low level effect of the other metal at low Ca. Such antagonistic interactions were smaller or became insignificant at higher Ca levels. The Cu EC10 was unaffected by Zn whereas the Zn EC10 increased by Cu at low Ca. These effects obeyed the BLM combined with the independent action model for toxicants. The BLM model explains the observed interactions by accounting for competition between both metals free ions and Ca2+ at the Cu and Zn biotic ligands. The implications of these findings for Cu/Zn interactions in soil are discussed
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