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991.
Laveda F Núñez-Delicado E García-Carmona F Sánchez-Ferrer A 《Journal of agricultural and food chemistry》2001,49(2):1003-1008
The kinetics of the activation process of latent peach PPO by trypsin was studied. By coupling this activation process to the oxidation of 4-tert-butylcatechol (TBC) to its corresponding quinone, it was possible to evaluate the specific rate constant of active PPO formation, k(3), which showed a value of 0.04 s(-1). This proteolytic activation of latent peach PPO permitted us to characterize the monophenolase activity of peach PPO for the first time using p-cresol as substrate, and it showed the characteristic lag period of the kinetic mechanism of monophenols hydroxylation, which depended on the enzyme and substrate concentration, the pH and the presence of catalytic amounts of o-diphenol (4-methylcatechol). The enzyme activation constant, k(act), was 2 microM. 相似文献
992.
993.
Jaciele Beserra de Lira Alberício Pereira de Andrade André Luiz Rodrigues Magalhães Fleming Sena Campos Gherman Garcia Leal de Araújo Diana Signor Deon 《Communications in Soil Science and Plant Analysis》2020,51(5):701-709
ABSTRACTThe objective is to determine the growth, yield and chemical characteristics of pearl millet irrigated with different levels of brackish water and organic matter in two cultivation cycles. The experimental design was randomized blocks in a 4 × 4 factorial arrangement, composed of 4 levels of brackish irrigation (25, 50, 75 and 100% evapotranspiration), 4 levels of organic matter (0, 15, 30 and 45 t ha?1) with 3 repetitions. Along two cultivation cycles, pearl millet crop was analyzed for: plant growth variables, fresh and dry mass production, water-use efficiency, and chemical composition. There was significant interaction between applied water levels and organic matter for lignin in the 2nd cut (P < .05). The number of leaves, number of dead leaves and fresh mass production were influenced by the isolated effect of brackish water levels in cut 1 (P < .05). In turn, fresh mass production, dry mass production, plant height, leaves length, panicle length, fresh mass production, crude protein and ether extract were influenced by the isolated effect of saline water levels in the 2nd cut (P < .05). Growth, biomass production and chemical composition variables in second cut are positively influenced by different brackish irrigation levels under low rainfall conditions. 相似文献
994.
María del Mar Alguacil Fuensanta Caravaca Gisela Díaz Purificacin Marín Antonio Roldn 《植物养料与土壤学杂志》2004,167(5):637-644
A field experiment was carried out to evaluate the effectiveness of mycorrhizal inoculation with three arbuscular mycorrhizal (AM) fungi (Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge), and Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe) and the addition of composted sewage sludge (SS) with respect to the establishment of Retama sphaerocarpa L. seedlings, in a semiarid Mediterranean area. Associated changes in soil chemical (nutrient content and labile carbon fractions), biochemical (enzyme activities), and physical (aggregate stability) parameters were observed. Six months after planting, both the addition of composted SS and the mycorrhizal‐inoculation treatments had increased total N content, available‐P content, and aggregate stability of the soil. Values of water‐soluble C and water‐soluble carbohydrates were increased only in the mycorrhizal‐inoculation treatments. Rhizosphere soil from the mycorrhizal‐inoculation treatments had significantly higher enzyme activities (dehydrogenase, protease‐BAA, acid phosphatase, and β‐glucosidase) than the control soil. In the short‐term, mycorrhizal inoculation with AM fungi was the most effective treatment for enhancement of shoot biomass, particularly with G. mosseae (about 146% higher with respect to control plants). The addition of the composted SS alone was sufficient to restore soil structural stability but was not effective with respect to improving the performance of R. sphaerocarpa plants. 相似文献
995.
Some recalcitrant organic wastes, which contain a large proportion of lignin or cellulose, are not changed much by composting, and thus the effectiveness of the compost as fertilizer is usua.lly low. In this study, incubation of unripe compost with ligno-cellulolytic microorganisms —Trichoderma viride orBacillus spp. — was investigated to increase the degree of humification of the organic matter present, and improve ils quality as a soil amendment. High-performance liquid chromatography (HPLC) analyses together with humification indices and electrofocusing patterns were used to monitor the evolution of the humic substances during the incubation process. Plant growth effects exerted by Azotobacter chroococcum on lettuce plants growing on the previously incubated compost were affected by the length of incubation and by changes in the composition of humic substances. Higher organic matter content and better humification seem to be important factors for predictingA. chroococcum hebaviour in the rhizosphere. 相似文献
996.
Marcos Gallo Alfredo Trento Ana Alvarez Horacio Beldoménico Darío Campagnoli 《Water, air, and soil pollution》2006,174(1-4):367-384
The objective of this work is to analyze Fe, Mn, Cr, Cd, Cu, Pb, and Zn distributions in the water column in terms of total, dissolved, and particulate concentrations in the Salado River (Santa Fe – Argentina); their relationship with total, dissolved and suspended solids; and the impact of two pollution sources on the watercourse: a stream that collects domestic and industrial wastewater discharges of the region and a direct discharge that releases urban and industrial effluents to the river. Water samples obtained from 5 surveys were analyzed. The Salado River transported a load of heavy metals that ranged from 700 g/s to 2200 g/s of Fe, 20 g/s to 60 g/s of Mn and 1 g/s to 3 g/s of Cr. Results show that most metals were found in particulate form, that the metal input from the direct discharge may be significant at low water levels, whereas a lesser impact was produced by the stream, and that both pollution sources were negligible at high water levels. 相似文献
997.
Solubility of purified lutein diesters obtained from Tagetes erecta in supercritical CO(2) and the effect of solvent modifiers 总被引:2,自引:0,他引:2
Naranjo-Modad S López-Munguía A Vilarem G Gaset A Bárzana E 《Journal of agricultural and food chemistry》2000,48(11):5640-5642
Purified lutein diesters deposited on commercial nonporous glass beads were solubilized in supercritical CO(2) in a computerized batch extractor, and their solubilities were compared to their solubilities in hexane. Densities of 0.7, 0.8, and 0.9 g/mL were evaluated without modifiers. Both pressure and temperature increased solubility, although temperatures >50 degrees C promoted carotenoid loss as determined by mass balance. Solubility was enhanced by the use of modifiers and was related to their log P. Chloroform (log P = 2) increased 2.8 times the amount of solubilized lutein diesters compared to pure CO(2) at the same extraction conditions (0.9 g/mL and 40 degrees C) to yield 65% of the amount extracted with hexane. Supercritical CO(2) extraction of lutein diesters could represent a cleaner technology as compared to the current industrial use of hexane with important ecological and health-related implications. 相似文献
998.
A complete study was made of 20 Spanish herbaria and of the literature concerning the regional flora of Spain in order to define the geographical limits of the different genera of the subtribe Hordeineae found in Spain. Accordingly, several expeditions were undertaken to the greater part of the Spanish mainland and its islands in order to collect samples of wild populations of the genera Hordeum L., Taeniatherum Nevski and Hordelymus Jessen. This paper, which contains information garnered from both collection activities and the study of herbaria, describes the distribution and ecological characteristics of the habitats where populations of H. bulbosum, H. secalinum, H. murinum subsp. murinum, H. murinum subsp. leporinum, H. marinum subsp. marinum, H. marinum subsp. gussoneanum, Taeniatherum caput-medusae and Hordelymus europeus grow.The bioclimatic and geographical characteristics of the populations of the different genera and species from which samples were taken during collect ing expeditions are also described. 相似文献
999.
E. Franco-Vizcaíno 《Biology and Fertility of Soils》1997,24(1):32-38
This study assessed differences in soil quality linked to differences in the diversity of residues returned to the soil in nine pairs of farm fields in central Michigan. To assure that management was the main difference within pairs, study sites were selected that mapped to the same soil series. Analysis of variance using subsamples as replicates for all nine comparisons revealed significantly higher maize (Zea mays L.) yield and total and mineralizable N for the high-diversity fields. Manuring history reported by farmers was difficult ro reconcile with levels of total C and extractable P. To account for uncertainty in manuring histories, comparisons were separated into four subsets on the Basis of residue diversity (DVS) and extractable P (high DVS high P, low DVS low P, high DVS low P, and low DVS high P). For these segregates, analysis of variance (ANOVA) using subsamples as replicates revealed significant improvements in 6 of 21 soil quality indices in the high-DVS-P subset. For all nine comparisons, correlation analysis revealed moderately strong relationships between total C, extractable P, as well as their ratio (Ctot/Pext), and both bulk density and log(infiltration time). When the data were segregated as before, these relationships were much stronger for the high-DVS high-P subset, and their slopes differed significantly from those of the other subsets, indicating that the data points originated from different populations. These results suggest a strong interaction between residue diversity, and P likely applied in manure, that influenced soil quality. 相似文献
1000.
Oxidation of the flavonol quercetin by polyphenol oxidase 总被引:5,自引:0,他引:5
Because direct oxidation of flavonols by polyphenol oxidase (PPO) has not previously been reported and, given the importance of flavonols, the ability of broad bean seed PPO to oxidize the flavonol quercetin was studied. The reaction was followed by recording spectral changes with time. Maximal spectral changes were observed at 291 nm (increase) and at 372 nm (decrease). The presence of two isosbectic points (at 272 and 342 nm) suggested the formation of only one absorbent product. These spectral changes were not observed in the absence of PPO. The oxidation rate, which varied with pH, was highest at pH 5.0. The following kinetic parameters were also determined: V(m) = 11 microM/min, K(m) = 646 microM, V(m)/K(m) = 17 x 10(-)(2) min(-)(1). Flavonol oxidation was efficiently inhibited (K(I) = 3.5 microM) by specific PPO inhibitors such as 4-hexylresorcinol. The results obtained showed that quercetin oxidation was strictly dependent on the presence of PPO. 相似文献