Nitrate uptake rates were determined for nonmycorrhizal and mycorrhizal maritime pine (Pinus pinaster) associated with the ectomycorrhizal basidiomycete Hebeloma cylindrosporum and for this fungal species grown in vitro. Different [NO3−] (0–1.3 and 10 mM) were supplied to nonmycorrhizal or mycorrhizal P. pinaster plants grown axenically in test tubes for 21 weeks. Uptake of NO3− by the plants was determined by measuring NO3− depletion from the medium that was added to the culture tubes without root pertubation. For all applied [NO3−] the uptake rates for NO3− in mycorrhizal plants were increased about twofold compared with nonmycorrhizal plants. The same range of [NO3−] was supplied to the fungus in pure culture, and uptake rates were calculated either from the measurement of NO3− depletion from the medium or by 15N accumulation in the mycelium. For the same external nitrate concentrations the results obtained with these two methods were not significantly different. The amount of fungal biomass in mycorrhizal root systems was determined with the chitin assay. The contribution of each partner to nitrate uptake in the mycorrhizal plant was calculated from the kinetic parameters of nitrate uptake by the fungus and host plant alone given by the Lineweaver–Burk plots. For external [NO3−] higher than 0.1 mM the measured uptake rates for NO3− in mycorrhizal plants were greater than the calculated sum of the individual symbiotic partners. The significance of this excess nitrate uptake is discussed in relation to the role of ectomycorrhizae in nitrogen accumulation. Key words: NO3− uptake rates, Km, Vmax, ectomycorrhizal symbiosis, Hebeloma cylindrosporum, Pinus pinaster.
Upgrading consists of a range of purification processes aimed at increasing the methane content of biogas to reach specifications similar to natural gas. In this perspective, an environmental assessment, based on the Life Cycle Assessment (LCA) method, of different upgrading technologies is helpful to identify the environmental characteristics of biomethane and the critical steps for improvement. The aim of this work is to conduct an LCA of biomethane production from waste feedstock, using the SimaPro software. The study focuses on the comparison of several upgrading technologies (namely, membrane separation, cryogenic separation, pressure swing adsorption, chemical scrubbing, high pressure water scrubbing) and the on-site cogeneration of electricity and heat, including the environmental benefits deriving from the substitution of fossil-based products. The results show a better environmental performance of the cogeneration option in most of the impact categories. The Fossil resource scarcity is the impact category which is mainly benefited by the avoided production of natural gas, with savings of about 0.5 kg oil eq/m3 of biogas for all the investigated technologies, with an average improvement of about 76% compared to conventional cogeneration. The results show that the membrane upgrading technology is slightly more environmentally convenient than the other upgrading technologies.
S U M M .\ R YGrowth, nitrogen uptake and mineral nutrient concentrations in the plant tissues were determined m nonmycorrhizal and mycorrhizal Norway spruce (Picea abies (L.) Karst.) seedhngs grown under controlled conditions in a semi-hydroponic culture system with quartz sand as substrate and a percolating nutrient solution. The culture system allowed the determination of nutrient uptake rates in mycorrhizal root systems with an intact extramatrical mycelium. The rate of infection of the roots by the mycorrhizal fungi Pisolithus tinctorius and Laccaria laccata was high but the rate of infection by Paxillus involutus was low.When supplied with ammonium nitrate, the d. wt of the roots and particularly of the shoots was .significantly lower in mycorrhizal than in non-mycorrhizal plants. Despite the lower root d. wt, the number of root tips and the root branching ratio (number of root tips per unit root length) were significantly higher in mycorrhizal plants infected with L. laccata and P. tinctorius than in non-mycorrhizal plants. The depletion of ammonium in the external solution was faster than the depletion of nitrate. Nitrate uptake rates increased at ammonium concentrations below 400/«l. The maximal N uptake rates (I^,,as)i calculated after Lineweaver-Burk. were significantly higher for ammonium than for nitrate. The N uptake rates did not differ significantly between nonmycorrhizal and mycorrhizai plants. The concentrations ot N, P, K, Ca and Alg tended to be higher in the smaller mycorrhiza! than in the larger non-mycorrhizal plants. .•\ significant increase in mineral nutrient concentration in mycorrhizal compared with non-mycorrhizal plants was found only for N concentrations in the needles of mycorrhizal plants infected with P. tinctorius.When they were supplied with ammonium ((NHj),SOj) as source of N, but not when they were supplied with nitrate (KNO,,), the d. wt was lower in mycorrhizal plants infected with P. tinctorius than it was in nonmycorrhizal plants, llierefore, N uptake rates were increased in mycorrhizal plants with P. tinctorius only when they were supplied with ammonium but not with nitrate.The insignificant differences in uptake rates of N, P, K, Ca and Mg between non-mycorrhizal and mycorrhizal plants indicate that at unlimited spatial nutrient availability the contribution of the extramatrical mycelium to nutrient uptake by mycorrhizal plants was small. It is suggested that the decreased growth of mycorrhizal plants is due to the demand of the mycorrhizal fungus for photosynthates, i.e. source limitation.
Natural populations of woody perennials on lead-mining sites in the Mechernich area of the Eifel Mountains were investigated with respect to soil factors determining the degree and type of heavy metal tolerance. Salix caprea L.
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